JP2009141944A - Image processing apparatus, image display device, and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image processing apparatus for eliminating a pseudo contour caused by a void in an image level. <P>SOLUTION: The image processing apparatus for applying high gradation to image data to compensate the gradation of the image data is provided with: a data bit expanding part 5 for increasing the number of bits of the image data and expanding the gradation of the image data; a threshold control part 29 for obtaining a threshold according to the gradation of the image data; a smoothing filter 60 for smoothing the predetermined gradation of the image data while preserving a predetermined edge in the image data according to the threshold; and an output part for outputting the image data processed by the smoothing filter 60. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image processing apparatus, an image display apparatus, and an image processing method for interpolating tone of image data of a digital image, and more particularly to suppression of generation of a pseudo contour of a digital image.

  In recent years, the brightness of display devices such as televisions and monitors has been increasing. As the luminance increases, the amount of change in luminance per unit gradation also increases, and the change point becomes noticeable even when the gradation changes gradually. Therefore, display devices with high gradation resolution such as a 10-bit liquid crystal panel have been developed. However, since digital broadcasts and the like distribute video in 8 bits, the display device is effective regardless of the gradation of 10 bits. The typical number of gradations remains 8 bits. For this reason, at least three image levels are missing, and in an image signal whose gradation changes gently, such as sunset or sea, the image level of the adjacent area changes in a stepped manner and looks like a pseudo contour. End up.

  When image data having a pseudo contour with a missing image level is relaxed by a smoothing process (simple averaging or the like), there is a problem that the image is blurred. In the gradation interpolation method described in Patent Document 1, such a phenomenon that the image level of an adjacent region changes stepwise and at least one image level is missing is defined as “gradation jump”. Yes. In the technique described in Patent Document 1, in order to eliminate the gradation jump without performing the smoothing process, the first and second image levels where the gradation jump exists are specified to determine the level. A target region for tonal interpolation is extracted, the target region is divided into (N + 1) divided regions, and gradations of the target region are interpolated by sequentially assigning N intermediate image levels.

Japanese Patent Laid-Open No. 10-84481

  However, the above conventional technique has a problem that the pseudo contour of the gradual change cannot be eliminated because the gradation interpolation processing is performed based on the data in the narrow area.

  The present invention has been made in view of the above, and an object thereof is to obtain an image processing device, an image display device, and an image processing method capable of suppressing the generation of a pseudo contour of a digital image.

In order to solve the above-described problems and achieve the object, the present invention provides an image processing apparatus that interpolates the gradation of image data, a threshold control unit that obtains a threshold according to the gradation of the image data, and a response according to the threshold And a smoothing filter unit that smoothes a predetermined gradation of the image data while preserving a predetermined edge in the image data, and an output unit that outputs the image data processed by the smoothing filter unit .
Further, the step of expanding the number of bits of the image data to expand the gradation of the image data, the step of obtaining a threshold value according to the gradation of the image data, and storing a predetermined edge in the image data according to the threshold value Smoothing a predetermined gradation of the image data.

  According to the present invention, the threshold value is obtained according to the gradation of the image data, and the predetermined gradation of the image data is smoothed while storing the predetermined edge in the image data according to the threshold value. There is an effect that the generation of the pseudo contour can be suppressed without impairing the degree.

  Embodiments of an image processing apparatus, an image display apparatus, an image processing method, and an image display method according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments.

Embodiment 1 FIG.
FIG. 1 is a diagram showing a configuration of an image display apparatus (including an image processing apparatus) according to Embodiment 1 of the present invention. The image display apparatus 100 according to Embodiment 1 smoothes the gradation (interpolated gradation) increased by bit extension using an ε filter (nonlinear digital filter), and increases the effective number of gradations. An image display device that displays an image. The image display device 100 can be applied to, for example, a liquid crystal television or a plasma television.

  The image display device 100 includes an input terminal 1, a receiving unit 2, a multi-gradation processing unit 3, and a display unit 4. Among these, the receiving unit 2 and the multi-gradation processing unit 3 constitute an image processing apparatus (an apparatus that increases the effective number of gradations).

  In this embodiment, as an example of the receiving unit 2, a case where the receiving unit 2 is an A / D converter that converts an analog image signal into digital image data will be described. Note that a tuner may be provided in the receiving unit 2 so that the composite signal is demodulated into a luminance or chromaticity signal inside the receiving unit 2 and then converted into digital image data. Alternatively, the receiving unit 2 may be a digital interface, and the receiving unit 2 may receive digital data from the input terminal 1 and output n (n is a natural number) bit image data DI.

  The input terminal 1 is a terminal for inputting the analog image signal SA, and outputs the input analog image signal SA to the receiving unit 2. The receiving unit 2 converts the analog image signal SA into n-bit image data DI and outputs it to the multi-gradation processing unit 3.

  The multi-gradation processing unit 3 includes an original data bit expansion unit 5, a gradation conversion unit 28, an ε selection unit 29 as a threshold control unit, and a one-dimensional m-order ε filter unit 60 as a smoothing filter unit. The n-bit image data DI is converted into (n + α) bits (multi-gradation) and output to the display unit 4. Note that m and α are both natural numbers.

  The original data bit extension unit 5 may be arranged before the one-dimensional mth-order ε filter unit 60. The original data bit expansion unit 5 outputs (n + α) -bit image data DJ obtained by extending the n-bit image data DI by α bits to the gradation conversion unit 28. The gradation conversion unit 28 performs gradation conversion such as gamma conversion and contrast correction on the image data DJ, and sets the image data after gradation conversion as the image data DS ((n + α) bits) and the ε selection unit 29. The result is output to the one-dimensional m-order ε filter unit 60.

  Each image data (image data DS, image data DI, image data DJ, and image data DO described later) input / output in the image display apparatus 100 is data indicating the values of pixels arranged in a matrix. The position of each pixel indicated by the image data DS is represented by coordinate values (i, j) (i and j are both natural numbers) with the upper left corner of the image as the origin (0, 0), and the horizontal coordinate value i Is incremented by 1 every time one column is moved to the right, and the vertical coordinate value j is incremented by 1 every time one row is moved downward. Each of these image data is a data string that sequentially indicates data arranged in a plurality of rows. This data column is a column of data indicating a plurality of rows in order from top to bottom and a plurality of pixels in each row in order from left to right.

  Conversion from analog image signal SA to image data DI in the receiving unit 2, supply of image data DI from the receiving unit 2 to the original data bit expansion unit 5, bit expansion (expansion of the number of bits) in the original data bit expansion unit 5, The supply of image data DJ from the original data bit expansion unit 5 to the gradation conversion unit 28 and the supply of image data DS from the gradation conversion unit 28 to the data storage unit 7 are performed by a pixel clock supplied from a control unit (not shown). Done in sync with The operation of other parts of the multi-gradation processing unit 3 described below is also performed in synchronization with the pixel clock supplied from the control unit.

  The ε selection unit 29 has a threshold value table set for each gradation, and a threshold value corresponding to the input image data DS (gradation DS) (any one of threshold data TH (1) to TH (m)). Are selected from the table (tone threshold correspondence information) and output to the one-dimensional m-th order ε filter unit 60. The threshold here is a value to be compared with difference data ED described later.

  The one-dimensional m-th order ε filter unit 60 is based on pixel data aligned in a one-dimensional direction with respect to a target pixel (a pixel serving as a reference when smoothing gradation) as a pixel to be processed, It is used as an edge preserving smoothing filter (ε filter) that performs smoothing by treating small amplitude components as noise while preserving steep changes (edges). The one-dimensional m-th order ε filter unit 60 smoothes the gradations increased by the original data bit expansion unit 5 to eliminate gradation jumps and increase the effective number of gradations.

  The one-dimensional m-th order ε filter unit 60 includes a data storage unit 7, a first difference calculation unit 8-1 to an m-th difference calculation unit 8-m, a first ε determination unit 9-1 to an m-th ε determination. Unit 9-m, determination additional weight average unit 10, and data addition unit 11.

  The data storage unit 7 stores the image data DS from the gradation conversion unit 28, and also stores the image data DM (1) to the first difference calculation unit 8-1 to the m-th difference calculation unit 8-m, respectively. Output DM (m). The data storage unit 7 outputs the image data DM (c) to the first difference calculation unit 8-1 to the m-th difference calculation unit 8-m and the data addition unit 11.

  The image data DM (c) is image data when the target pixel is the target pixel c. Each of the image data DM (1) to DM (m) is image data of pixels separated from the target pixel c by a predetermined number of pixels (coordinate values) in the right direction or the left direction. For example, when m = 5, if the image data DM (3) is the image data DM (c), the image data DM (1) becomes the image data of the pixel two pixels before (on the left side) of the pixel of interest c. The data DM (2) is the image data of the pixel immediately before (on the left side) the pixel of interest c, and the image data DM (4) is the image data of the pixel after the pixel of interest c (on the right side). (5) is the image data of the pixel after (right side) two pixels after the target pixel c.

  The first difference calculation unit 8-1 to the m-th difference calculation unit 8-m represent differences between the image data DM (1) to DM (m) and the image data DM (c) as difference data (difference values), respectively. ) Calculated as ED (1) to ED (m). The first difference calculation unit 8-1 to the m-th difference calculation unit 8-m respectively send the difference data ED (1) to the first ε determination unit 9-1 to the m-th ε determination unit 9-m. ED (m) is output.

  The first ε determination unit 9-1 to the m-th ε determination unit 9-m are difference data ED (1) to ED (1) to -1 (m) from the first difference calculation unit 8-1 to the m-th difference calculation unit 8-m, respectively. It is determined whether or not ED (m) is larger than the threshold data TH (1) to TH (m) from the ε selector 29, and the determination result is determined as determination data EE (1) to EE (m). Output to the weighted average unit 10.

  The determination additional weight average unit 10 performs weighted average of the difference data ED (1) to ED (m) based on the determination data EE (1) to EE (m), and the weighted average value obtained as a result thereof is weighted average value. (Average data) Output to the data adder 11 as EM. The data adding unit 11 adds the image data DS (image data DM (c)) to the weighted average value EM.

  The above processing is performed on the image data DS with each pixel as a target pixel in order, and the image data (n + α-bit data) subjected to these processings is transferred from the data adding unit 11 of the one-dimensional m-order ε filter unit 60 to the image data DS. It outputs to the display part 4 as data DO. The display unit 4 is a display unit such as a liquid crystal monitor that displays (n + α) -bit image data DO.

  Here, the ε filter included in the one-dimensional m-order ε filter unit 60 will be described. The ε filter is described in, for example, Non-Patent Document 1 (supervised by Takao Hinamoto, Mitsuji Muneyasu, Ryo Otaguchi, “Nonlinear Digital Signal Processing”, Asakura Shoten, March 20, 1999, p. 106-107). Yes.

One-dimensional processing by the ε filter is expressed by Expression (1). In Expression (1), x (i) is the gradation of the input image data, and y (i) is the gradation of the output image data. Further, a _k is a coefficient, k is a relative pixel position from the target pixel, and ε is a threshold value.

FIG. 2 is a diagram illustrating the function f (u) of the equation (1). When the absolute value of u is less than or equal to the threshold ε, f (u) = u, and when the absolute value of u is greater than the threshold ε, f (u) = 0. In the case of the example shown in Expression (1), x (ik) −x (i) is supplied to the ε filter as u. When the difference x (ik) −x (i) between the gradation x (i) at the pixel position i and the gradation x (ik) at the pixel position (ik) around the pixel position i is small , F (u) = f {x (ik) -x (i)} is approximately linear. Assuming that the sum of the coefficients a _k is 1, Expression (1) is rewritten to Expression (2), and the ε filter is equal to the weighted average value filter.

  Also, equation (1) can be rewritten as equation (3).

  When x ′ (ik) newly defined when the nonlinear function of FIG. 2 is applied to f (u) of Equation (3), Equation (3) can be rewritten as Equation (4). Can do. In Expression (4), x ′ (ik) becomes x (ik) when the difference x (ik) −x (i) is less than or equal to the threshold ε, and the difference x (ik) − When x (i) is larger than the threshold ε, x (i) is obtained.

FIG. 3 is a diagram for explaining the ε filter processing by the ε filter. FIG. 3 shows the relationship between the pixel position and the gradation (gradation for each pixel position). A graph 201a shown in the upper part of FIG. 3 shows an input signal to the ε filter. Also, a graph 201b shown in the lower left part of FIG. 3 shows processing on the target pixel (point A) by the ε filter, and a graph 201c shown in the lower right part of FIG. 3 shows the target pixel (point B) by the ε filter. Shows the processing. In each of the graphs 201a to 201c, the horizontal axis is the pixel position i, and the vertical axis is the gradation of the input x (i).

  When the ε filter using the function f (u) in FIG. 2 processes the signal at the point A shown in the graph 201a, the gray level having a difference larger than ± ε from the gray level at the point A as shown in the graph 201b. All of them are replaced with the gradation of point A, and the weighted average is obtained. Therefore, the gradation is not affected by large amplitude signal components such as edges.

  Further, the ε filter using the function f (u) in FIG. 2 has a difference larger than ± ε from the gradation of the point B as shown in the graph 201c when processing the signal at the point B shown in the graph 201a. All the tones are replaced with the tone of point B, and the weighted average is obtained.

  In other words, even at an edge portion such as point B, as shown in the graph 201c, an average of pixels having values close to the pixel value of the edge is taken, and edge deterioration does not occur. As a result, the ε filter can remove small amplitude noise while maintaining a sharp change in signal such as an edge.

In this way, the ε filter treats the gradation increased by bit expansion as small amplitude noise (treats it as small amplitude noise) and performs ε filter processing. That is, when bit expansion is performed from n bits to (n + α) bits, the threshold ε of the ε filter is set to 2 ^α (2 ^ α). By doing so, the ε filter can increase the effective number of gradations while maintaining a sharp change in the image such as the contour. However, when gradation conversion such as gamma conversion is performed between bit expansion and ε filter processing, the size of gradation increased by bit expansion changes.

  Therefore, in the present embodiment, the image display apparatus 100 includes an ε selection unit 29 (threshold control unit) that changes the threshold ε according to the input gradation, and a one-dimensional m-th order in which the threshold is controlled by the ε selection unit 29. The threshold value ε is changed in accordance with the gradation conversion. That is, the edge size that can be stored in the ε filter is changed according to the input gradation. This will be described in detail below.

  FIG. 4 is a diagram showing the relationship between gradation and threshold. In FIG. 4, a table showing threshold values for each gradation is graphed. When the ε selection unit 29 corresponding to the threshold control unit has a table indicating threshold values for each gradation shown in FIG. 4, the ε filter retains a small edge in a small gradation region and is large in a large gradation region. Keep only edges.

  As described above, the input image includes the ε selection unit 29 (threshold control unit) and the one-dimensional m-order ε filter unit 60 (edge-preserving smoothing filter) whose threshold is controlled by the ε selection unit 29. It operates as a smoothing filter in which the edge to be held differs according to the gradation. For example, if the threshold control unit is set to increase the threshold when the gradation is low, the region with a low gradation level can be smoothed more strongly than the other regions.

  Hereinafter, as an example of multi-gradation processing, a case where α = 2, that is, a case where an n-bit image is subjected to multi-gradation processing to n + 2 bits will be described. FIG. 5 is a diagram illustrating the configuration of the image display apparatus according to the first embodiment when m = 4. Of the constituent elements in FIG. 5, constituent elements that achieve the same functions as those of the image display device 100 shown in FIG. 1 are given the same numbers, and redundant descriptions are omitted.

  The image display apparatus 101 includes a one-dimensional fourth-order ε filter unit 61 instead of the one-dimensional m-order ε filter unit 60. The one-dimensional fourth-order ε filter unit 61 includes a first difference calculation unit 8-1 to a fourth difference calculation unit 8-4, and a first ε determination unit 9-1 to a fourth ε determination unit 9-4. It is comprised including.

  In the image display apparatus 100 shown in FIG. 1, the image data DM (1) to DM (m) are input to the first difference calculation unit 8-1 to the m-th difference calculation unit 8-m. In the illustrated image display apparatus 101, image data DM (l2), DM (l1), DM (c), DM is input to the first difference calculation unit 8-1 to fourth difference calculation unit 8-4. (R1). Image data represented by image data DM (l2), DM (l1), DM (c), DM (r1) is image data DM (1), DM (2), DM (when m = 4, respectively. 3) The same as DM (4).

  The image data DM (c) is image data of the target pixel c, and is data representing the gradation DM (c). The image data DM (l1) is the image data of the pixel l1 immediately before the pixel c of interest (next to the left) (the difference in the coordinate value i in the horizontal direction is 1), and is data representing the gradation DM (l1). . The image data DM (l2) is image data of the pixel l2 which is two pixels before the target pixel c (the difference in the coordinate value i in the horizontal direction is 2), and is data representing the gradation DM (l2). The image data DM (r1) is image data of the pixel r1 that is one pixel after the target pixel c (next to the right) (the difference in the coordinate value i in the horizontal direction is 1), and is data representing the gradation DM (r1). is there.

  The difference data ED (l2) to (r1) output from the first difference calculation unit 8-1 to the fourth difference calculation unit 8-4, the first ε determination unit 9-1 to the fourth ε determination The determination data EE (l2) to EE (r1) output from the unit 9-4 are also the difference data ED (1) to ED (4) and the determination data EE (1) to EE (4) when m = 4, respectively. ). Also, the threshold data TH (l2) to TH (r1) output from the ε selector 29 are the same as the threshold data TH (1) to TH (4) when m = 4, respectively.

  FIG. 6 is a diagram for explaining the A / D conversion processing by the receiving unit. FIG. 6 shows the relationship between the analog signal SA and the image data DI. The vertical axis of the graphs 202a and 202b shown in FIG. 6 indicates the gradation, and the horizontal axis indicates the pixel position i. The graph 202a shows the gradation of the analog image signal SA, and the graph 202b shows the gradation of the digital image data DI.

  In the image display device 101, an analog image signal SA shown in the graph 202 a is input from the input terminal 1 to the receiving unit 2. The receiving unit 2 converts the analog image signal SA into n-bit image data DI as shown in the graph 202b and outputs the converted image data to the multi-gradation processing unit 3. In the multi-gradation processing unit 3, n-bit image data DI is input to the original data bit expansion unit 5.

  The image signal SA (gradation gradually changing signal) shown in the graph 202a has a gradual change in gradation, and the quantization resolution with respect to the change in gradation is low (the number of bits is small). In the case of the image data DI, binary gradation (X and X + 1) is converted.

  FIG. 7 is a diagram for explaining bit extension processing by the original data bit extension unit. FIG. 7 shows the relationship between the image data DI and the image data DJ. The vertical axis of the graphs 203a and 203b shown in FIG. 7 indicates the gradation, and the horizontal axis indicates the pixel position i. The graph 203a shows the gradation of the n-bit image data DI, and the graph 203b shows the gradation of the (n + 2) -bit image data DJ.

  The original data bit extension unit 5 bit-extends n-bit image data DI as shown in the graph 203a by 2 bits, and converts the (n + 2) -bit image data DJ as shown in the graph 203b into a one-dimensional fourth-order ε filter unit. To 61. Since the (n + 2) -bit image data DJ as shown in the graph 203b is bit-extended by 2 bits, the gradation of the image data DJ in the graph 203a is converted from the gradation X to the gradation 4X, and the gradation ( X + 1) is converted to gradation 4 (X + 1).

  FIG. 8 is a diagram for explaining gradation conversion processing by the gradation conversion unit. FIG. 8 shows the relationship between the image data DJ and the image data DS. The vertical axis of the graphs 204a and 204b shown in FIG. 8 indicates the gradation, and the horizontal axis indicates the pixel position i. The graph 204a shows the gradation of the n-bit image data DJ, and the graph 204b shows the gradation of the image data DS after gradation conversion. The gradation conversion unit 28 performs various gradation conversions such as gamma conversion and contrast correction. Here, the gradation conversion unit 28 converts gradation 4X into gradation 4Y and converts gradation 4 (X + 1) into gradation 4 (Y + 1) by performing various gradation conversions. .

  When the image data DS is near 4Y, all of the threshold data TH (l2) to TH (r1) are output as “4”, and when the image data DS is near 4 (Y + 1), the threshold data TH (l2) to TH (r1) are output. ) Is set in advance so as to output all “8” as “8”.

  The data storage unit 7 is configured as shown in FIG. 9, for example. FIG. 9 is a diagram illustrating an example of a detailed configuration of the data storage unit. The data storage unit 7 includes four flip-flops FF_1 to FF_4 connected in cascade, and the input image data DS is synchronized with the pixel clock by the four flip-flops FF_1 to FF_4. The data is transferred to the ε determination unit 9-1 to the fourth ε determination unit 9-4. That is, the data storage unit 7 supplies the input image data DS to the flip-flop FF_1, supplies the output of the flip-flop FF_1 to the input of the flip-flop FF_2, and outputs the output of the flip-flop FF_2 to the input of the flip-flop FF_3. The output of the flip-flop FF_3 is supplied to the input of the flip-flop FF_4, and the flip-flops FF_1 to FF_4 hold the image data DS, respectively.

  As a result, the input data for four consecutive pixels can be simultaneously held by the four flip-flops FF_1 to FF_4 and simultaneously output. Specifically, the data held in the flip-flop FF_2 is output as data representing the gray level DM (c) of the target pixel c, and the data held in the flip-flop FF_3 is the gray level DM of the pixel l1. The data output as data representing (l1) and held in the flip-flop FF_4 is output as data representing the gradation DM (l2) of the pixel l2, and the data held in the flip-flop FF_1 is output as the pixel r1. Is output as data representing the gray level DM (r1).

  FIG. 10 is a diagram for explaining the gradation of the image data output from the data storage unit. FIG. 10 shows the output of the data storage unit 7 when the pixel at the pixel position ic is the target pixel. The vertical axis of the graph 205 shown in FIG. 10 indicates the gradation of the image data DS input to the data storage unit 7 and the image data DM output from the data storage unit 7, and the horizontal axis indicates the pixel position i.

  In the example shown in FIG. 10, the data storage unit 7 outputs gradation DM (l2) = 4Y, gradation DM (l1) = 4Y, gradation DM (c) = 4Y, gradation DM (r1) = 4Y + 4. Then, the data output from the data storage unit 7 is supplied to the first difference calculation unit 8-1 to the fourth difference calculation unit 8-4, respectively. As described above, the data storage unit 7 stores the image data DM (c) of the pixel of interest at the pixel position ic and the image data DM (l2) and DM (l1) of the pixels around the pixel of interest that are continuous to the pixel of interest. , DM (r1) are simultaneously output.

  The first difference calculation unit 8-1 illustrated in FIG. 5 generates difference data ED (l2) between the gradation DM (l2) of the pixel l2 and the gradation DM (c) of the pixel of interest c, It outputs to the epsilon determination part 9-1 and the determination additional weight average part 10. FIG. Further, the second difference calculation unit 8-2 generates difference data ED (l1) between the gradation DM (l1) of the pixel l1 and the gradation DM (c) of the pixel of interest c, and the second ε determination unit 9-2 and the determination additional weight average unit 10. Further, the third difference calculation unit 8-3 generates difference data ED (c) between the gradation DM (c) of the pixel of interest c and the gradation DM (c) of the pixel of interest c, and the third ε determination Output to the unit 9-3 and the determination additional weight average unit 10. The fourth difference calculation unit 8-4 generates difference data ED (r1) between the gradation DM (r1) of the pixel r1 and the gradation DM (c) of the target pixel c, and a fourth ε determination unit. 9-4 and the determination additional weight average unit 10.

  As described above, the difference calculation units 8-1 to 8-4 include the image data DM (c) of the target pixel and the image data DM (l2) and DM () of the pixels around the target pixel that are continuous to the target pixel. c), a difference from each of DM (l1) and DM (r1) is calculated, and difference data ED (l2), ED (l1), ED (c), and ED (r1) representing the difference are output.

  FIG. 11 is a diagram showing data generated by the image display apparatus according to Embodiment 1 when the gradation changes gently. In FIG. 11, when the pixel at the pixel position ic shown in FIG. 10 is the target pixel P (c), the image data DM (k) and the difference data ED ( k), determination data EE (k), f {ED (k)}, weighted average value EM, and threshold data TH (k).

  The image data DM (k) in FIG. 11 is image data output from the data storage unit 7, and the difference data ED (k) is the first difference calculation unit 8-1 to the fourth difference calculation unit 8-4. Is data calculated based on the image data DM (k). The determination data EE (k) is data (determination result) calculated by the first ε determination unit 9-1 to the fourth ε determination unit 9-4, and the weighted average value EM is a determination additional weight. This is data generated by the averaging unit 10. Further, the threshold data TH is data output from the selection unit 29, and f {ED (k)} is a value obtained in the process of calculation by the determination additional weight average unit 10.

  The first difference calculation unit 8-1 outputs ED (l2) = DM (l2) -DM (c) = 4Y-4Y = 0, and the second difference calculation unit 8-2 outputs ED (l1). = DM (l1) -DM (c) = 4Y-4Y = 0, and the second difference calculation unit 8-3 outputs ED (c) = DM (c) -DM (c) = 4Y-4Y = 0 is output, and the fourth difference calculation unit 8-4 outputs ED (r1) = DM (r1) -DM (c) = (4Y + 4) -4Y = 4.

  The ε selection unit 29 is set to output all threshold data TH (l2) to TH (r1) as “4” when the image data DS is near 4Y. Therefore, in the case of image data DS = 4Y and image data DS = 4Y + 4, threshold data TH (l2) = 4, threshold data TH (l1) = 4, threshold data TH (c) = 4, threshold data TH (r1) = 4 are input to the first ε determination unit 9-1 to the fourth ε determination unit 9-4, respectively.

  The first ε determination unit 9-1 to the fourth ε determination unit 9-4 receive the difference data ED (k) and the threshold data TH (k), and the difference data ED (k) is the threshold data TH (k). It is determined whether or not it is larger.

  The first ε determination unit 9-1 to the fourth ε determination unit 9-4 determine whether or not the difference data ED (k) is larger than the threshold value data TH (k). It outputs to determination additional weight average part 10 as EE (k). That is, the first ε determination unit 9-1 to the fourth ε determination unit 9-4 set “0” as EE (k) when the difference data ED (k) is larger than the threshold data TH (k). When the difference data ED (k) is equal to or less than the threshold data TH (k), “1” is output as EE (k).

  Specifically, the first ε determination unit 9-1 generates “0” when the difference data ED (l2) is larger than the threshold data TH (l2), and the difference data ED (l2) is the threshold data. If it is less than TH (l2) (ε), “1” is generated. The second ε determination unit 9-2 generates “0” when the difference data ED (l1) is larger than the threshold data TH (l1), and the difference data ED (l1) is the threshold data TH (l1). ) "1" is generated in the following cases. The third ε determination unit 9-3 generates “0” when the difference data ED (c) is larger than the threshold data TH (c), and the difference data ED (c) is the threshold data TH (c ) "1" is generated in the following cases. Further, the fourth ε determination unit 9-4 generates “0” when the difference data ED (r1) is larger than the threshold data TH (r1), and the difference data ED (r1) is the threshold data TH (r1). ) "1" is generated in the following cases.

  As described above, the first ε determination unit 9-1 to the fourth ε determination unit 9-4 are based on the difference data ED (l1) to ED (r1) and the threshold data TH (l1) to TH (r1). Thus, determination data EE (l1) to EE (r1) are generated. Then, the generated determination data EE (l1) to EE (r1) are supplied to the determination additional weight average unit 10.

  In the example illustrated in FIG. 11, “0” is input to the first to third ε determination units 9-1 to 9-3 as difference data ED (l2), ED (l1), and ED (c), respectively. Then, “4” is input as the difference data ED (r1) to the fourth ε determination unit 9-4. Since the difference data ED (l2) to ED (r1) is equal to or less than the respective threshold data TH (l2) to TH (r1), the determination data EE (l2) to EE (r1) are all “1”. "

The determination additional weight average unit 10 performs weighted averaging of the difference data ED (l2) to ED (r1) based on the determination data EE (l2) to EE (r1), and outputs a weighted average value EM obtained as a result. . When the determination data EE (k) is “1”, the determination additional weight average unit 10 multiplies and adds the difference data ED (k) to the coefficient _ak , and the determination data EE (k) is “0”. Is not added. In other words, the determination additional weight average unit 10 performs a function (f {ED (k)}, which will be described later, etc.) represented by a predetermined expression on the difference data ED (k) according to the value of the determination data EE (k). ) To obtain the weighted average.

  FIG. 12 is a diagram for explaining the concept of the weighted average. The graph 206a shown in the upper side of FIG. 12 includes difference data ED (k) input to the first ε determination unit 9-1 to the fourth ε determination unit 9-4 and the first ε determination unit 9-1. It is a figure which shows the relationship of the determination data EE (k) output from the 4th (epsilon) determination part 9-4.

  The lower graph 206b shows difference data ED (k) input to the determination additional weight average unit 10 and difference data f {ED ( k)}.

  The first ε determination unit 9-1 to the fourth ε determination unit 9-4 determine the determination data based on the difference data ED (l1) to ED (r1) and the threshold data TH (l1) to TH (r1). EE (l1) to EE (r1) are generated. Then, the generated determination data (11) to EE (r1) are supplied to the determination additional weight average unit 10.

  As shown in the graph 206b, when the absolute value of the difference data ED (k) is less than or equal to the threshold ε, f {ED (k)} = ED (k), and the absolute value of the difference data ED (k) is the threshold. If it is greater than ε, f {ED (k)} = 0. As described above, the determination additional weight average unit 10 performs an operation for obtaining a weighted average of the difference data ED (l1) to ED (r1) so that the function f {ED (k)} having the relationship shown in the graph 206b is obtained. .

When all the coefficients a _k (= a _l2, a _l1 , a _c , a _r1 ) are set to 0.25, in the example shown in FIG. 11, all of the determination data EE (l2) to EE (r1) are “1”. Therefore, the output (weighted average value EM) of the determination additional weight average unit 10 is given by the following equation (5).
EM
= A _l2 × ED (l2) + a _l1 × ED (l1) + a _c ED (c) + a _r1 × ED (r1)
= (0.25 × 0) + (0.25 × 0) + (0.25 × 0) + (0.25 × 4)
= 1
... (5)

  In the image display device 100, the above processing (weighted average calculation processing) is performed on the image data DS supplied from the original data bit expansion unit 5 with each pixel as a target pixel in order. An operation is performed.

  FIG. 13 is a diagram illustrating a weighted average value of image data output from the data storage unit illustrated in FIG. 10. FIG. 13 shows the weighted average value EM (the weighted average value EM when the pixel at each pixel position i is the target pixel) corresponding to the image data DM. In the graph 207 shown in FIG. 13, the horizontal axis indicates the pixel position i of the target pixel, and the vertical axis indicates the gradation of the weighted average value EM. The determination additional weight average unit 10 outputs the weighted average value EM to the data addition unit 11.

  FIG. 14 is a diagram for explaining data addition processing by the data addition unit. In the graphs 208a to 208c of FIG. 14, the horizontal axis indicates the pixel position i, and the vertical axis indicates the gradation. The graph 208a shows the gradation of the image data DS, the graph 208b shows the gradation of the weighted average value EM, and the graph 208c shows the gradation of the image data DO.

  The data adding unit 11 adds the image data DS shown in the graph 208a and the weighted average value EM shown in the graph 208b, and outputs the image data DO shown in the graph 208c. For example, at the pixel position ia in the graphs 208a to 208c, since DS (ia) = 4Y and EM (ia) = 1, DO (ia) = DS (ia) + EM (ia) = 4Y + 1.

As described above, in this embodiment, the effective number of gradations in a region where the gradation change is gradual can be increased. When an n-bit image is converted into n + 2 bits, the image signal SA changes gradually. When the gradation of the image data DS obtained by bit-expanding the image signal SA jumps from 4Y to 4Y + 4 (only 4 = 2 ² ) as shown in the graph 208a, the gradation is changed as shown in the graph 208c. The gradation of the image data can be interpolated using 4Y + 1, 4Y + 2, 4Y + 3.

  Next, an operation when an analog image signal SA whose gradation changes sharply and greatly is input to the ε filter will be described. FIG. 15 is a diagram for explaining an operation in a case where an analog image signal whose gradation changes sharply and greatly is input to the image display device according to the first embodiment. In the graphs 209a to 209f shown in FIG. 15, the horizontal axis indicates the pixel position i, and the vertical axis indicates the gradation.

  The graph 209a shows the gradation of the analog image signal SA, the graph 209b shows the gradation of the n-bit image data DI, and the graph 209c shows the (n + α) -bit image data DJ. The graph 209d shows the gradation of the (n + α) -bit image data DS and the image data DM, the graph 209e shows the gradation of the weighted average value EM, and the graph 209f shows the gradation of the (n + α) -bit image data DO. Is shown.

  An analog image signal SA as shown in the graph 209a is input from the input terminal 1 to the receiving unit 2 to the image display device 100. The receiving unit 2 converts the analog image signal SA into digital image data DI (n bits) (binary gradation (X and X + 2)) as shown in the graph 209 b and outputs the converted data to the original data bit expansion unit 5. To do. In other words, the image signal SA (gradual gradation change signal) shown in the graph 209a has a sharply large change in gradation, and the quantization resolution with respect to the change in gradation is high (the number of bits is large). In the image data DI shown in (2), it is converted into binary gradations (X and X + 2).

  The original data bit expansion unit 5 converts the gradation X of the image data DI of the graph 209b into gradation 4X, converts the gradation (X + 2) into gradation 4 (X + 2), and produces image data as shown in the graph 209c. DJ is output to the gradation conversion unit 28.

  Here, the gradation conversion unit 28 performs gradation conversion from gradation 4X to gradation 4Y and gradation conversion from gradation 4 (X + 2) to gradation 4 (Y + 2), as shown in a graph 209d. The image data DS is output to the one-dimensional fourth-order ε filter unit 61.

  FIG. 16 is a diagram illustrating data generated by the image display apparatus according to Embodiment 1 when the gradation changes sharply. In FIG. 16, when the pixel at the pixel position ic in the graph 209d is the target pixel P (c), the difference data ED (k) generated based on the image data DM (k) and the image data DM (k). , Determination data EE (k), f {ED (k)}, weighted average value EM, and threshold data TH (k) are shown.

  The data storage unit 7 calculates DM (l2) = 4Y, DM (l1) = 4Y, DM (c) = 4Y, DM (r1) = 4Y + 8, respectively, as the first difference calculation unit 8-1 to fourth difference calculation. Output to section 8-4.

  The first difference calculation unit 8-1 outputs ED (l2) = DM (l2) -DM (c) = 4Y-4Y = 0, and the second difference calculation unit 8-2 outputs ED (l1). = DM (l1) -DM (c) = 4Y-4Y = 0, and the third difference calculation unit 8-3 outputs ED (c) = DM (c) -DM (c) = 4Y-4Y = 0 is output, and the fourth difference calculation unit 8-4 outputs ED (r1) = DM (r1) -DM (c) = (4Y + 8) -4Y = 8. Accordingly, “0” is input to the first ε determination unit 9-1 to the third ε determination unit 9-3, and “8” is input to the fourth ε determination unit 9-4.

  The ε selection unit 29 is set to output all threshold data TH (l2) to TH (r1) as “4” when the image data DS is near 4Y. Therefore, when the image data DS = 4Y and the image data DS = 4Y + 8, the threshold data TH (l2) = 4, the threshold data TH (l1) = 4, the threshold data TH (c) = 4, and the threshold data TH (r1) = 4 are input to the first ε determination unit 9-1 to the fourth ε determination unit 9-4, respectively.

  Since the difference data ED (l2) to ED (c) is equal to or less than the respective threshold data TH (l2) to TH (c), the determination data EE (l2) to EE (c) is “1”, and the difference data ED Since (r1) is larger than the threshold data TH (r1), the determination data EE (r1) is “0”.

When the determination data EE (k) is “1”, the determination additional weight average unit 10 multiplies and adds the difference data ED (k) to the coefficient _ak , and the determination data EE (k) is “0”. Is not added. When all of the coefficients a _k (= a _l2, a _l1 , a _c , a _r1 ) are 0.25, in the example shown in FIG. 16, the output (weighted average value EM) of the determination additional weight average unit 10 is It is given by the following equation (6).
EM
= A _l2 × ED (l2) + a _l1 × ED (l1) + a _c × ED (c)
= (0.25 × 0) + (0.25 × 0) + (0.25 × 0)
= 0
... (6)

  In the image display device 100, the above processing is performed on the image data DS supplied from the original data bit expansion unit 5 with each pixel as a target pixel in order, and the same calculation as Expression (6) is performed.

  A graph 209e indicates the gradation of the weighted average value EM (the weighted average value EM when the pixel at each pixel position i is the target pixel) corresponding to the image data DM of the graph 209d. The determination additional weight average unit 10 outputs the weighted average value EM to the data addition unit 11. The data adding unit 11 adds the image data DS shown in the graph 209d and the weighted average value EM shown in the graph 209e, and outputs the image data DO shown in the graph 209f.

  As shown in the graph 209f, the image data DO has a steep change similarly to the input (analog image signal SA) or the image data DI. In this way, the ε filter can maintain the sharpness of a region that changes drastically when the change in gradation is large.

  Next, the gradation of the image display device 101 changes gradually as in the graph 202a of FIG. 6, but an analog image signal SA (hereinafter referred to as a gradual change of gradation) in which the gradation jump increases when the gradation conversion is performed. The operation of the image display apparatus 101 when an analog image signal for conversion jump is input) will be described.

  FIG. 17 is a diagram for explaining an operation when an analog image signal that undergoes a conversion jump at a gradual gradation is input to the image display device according to the first embodiment. In the graphs 210a to 210f shown in FIG. 17, the horizontal axis indicates the pixel position i, and the vertical axis indicates the gradation.

  The graph 210a shows the gradation of the analog image signal SA (analog image signal that undergoes conversion jump with a gradual gradation), the graph 210b shows the gradation of the n-bit image data DI, and the graph 210c has (n + α) bits. Image data DJ is shown. The graph 210d shows the gradation of the (n + α) -bit image data DS and the image data DM, the graph 210e shows the gradation of the weighted average value EM, and the graph 210f shows the gradation of the (n + α) -bit image data DO. Is shown.

  An analog image signal SA shown in the graph 210 a is input from the input terminal 1 to the receiving unit 2 to the image display device 100. The receiving unit 2 converts the analog image signal SA into digital image data DI (n bits) (binary gradations (X ′ and X ′ + 1)) shown in the graph 210 b, and sends the converted data to the original data bit expansion unit 5. Output. The gradation X ′ and gradation (X ′ + 1) here are gradations different from the gradation X and gradation (X + 1), and the gradation jump becomes large when gradation conversion is performed. Key.

  The original data bit extension unit 5 converts the gradation X ′ of the image data DI of the graph 210b to gradation 4X ′, converts the gradation (X ′ + 1) to gradation 4 (X ′ + 1), and displays the graph 210c. The image data DJ as shown in FIG.

  Here, the gradation converting unit 28 performs gradation conversion from gradation 4X ′ to gradation 4Z, gradation conversion from gradation 4 (X ′ + 1) to gradation 4 (Z + 2), and graph 210d. The image data DS as shown (image data DS with a large gradation jump) is output to the one-dimensional fourth-order ε filter unit 61.

  FIG. 18 is a diagram illustrating data generated by the image display apparatus according to the first embodiment when an analog image signal that undergoes a conversion jump at a gradual gradation is input. In FIG. 18, image data DM (k) and difference data ED (k) generated based on the image data DM (k) when the pixel at the pixel position ic in the graph 210d is the target pixel P (c). , Determination data EE (k), f {ED (k)}, weighted average value EM, and threshold data TH (k) are shown.

  The data storage unit 7 sets DM (l2) = 4Z, DM (l1) = 4Z, DM (c) = 4Z, DM (r1) = 4Z + 8, respectively, as the first difference calculation unit 8-1 to fourth difference calculation. Output to section 8-4.

  The first difference calculation unit 8-1 outputs ED (l2) = DM (l2) -DM (c) = 4Z-4Z = 0, and the second difference calculation unit 8-2 outputs ED (l1). = DM (l1) -DM (c) = 4Z-4Z = 0 is output, and the third difference calculation unit 8-3 outputs ED (c) = DM (c) -DM (c) = 4Z-4Z = 0 is output, and the fourth difference calculation unit 8-4 outputs ED (r1) = DM (r1) -DM (c) = (4Z + 8) -4Z = 8. Accordingly, “0” is input to the first ε determination unit 9-1 to the third ε determination unit 9-3, and “8” is input to the fourth ε determination unit 9-4.

  The ε selection unit 29 is set to output all threshold data TH (l2) to TH (r1) as “8” when the image data DS is near 4Z. Therefore, in the case of image data DS = 4Z and image data DS = 4Z + 8, threshold data TH (l2) = 8, threshold data TH (l1) = 8, threshold data TH (c) = 8, threshold data TH (r1) = 8 are input to the first ε determination unit 9-1 to the fourth ε determination unit 9-4, respectively. Since the difference data ED (l2) to ED (r1) is equal to or less than the respective threshold data TH (l2) to TH (r1), the determination data EE (l2) to EE (r1) is “1”.

When the determination data EE (k) is “1”, the determination additional weight average unit 10 multiplies and adds the difference data ED (k) to the coefficient _ak , and the determination data EE (k) is “0”. Is not added. When all the coefficients a _k (= a _l2, a _l1 , a _c , a _r1 ) are set to 0.25, the output (weighted average value EM) of the determination additional weight average unit 10 in the example shown in FIG. It is given by the following equation (7).
EM
= A _l2 × ED (l2) + a _l1 × ED (l1) + a _c ED (c) + a _r1 × ED (r1)
= (0.25 × 0) + (0.25 × 0) + (0.25 × 0) + (0.25 × 8)
= 2
... (7)

  In the image display device 100, the above processing is performed on the image data DS supplied from the original data bit expansion unit 5 with each pixel as a target pixel in order, and the same calculation as Expression (7) is performed.

  A graph 210e indicates the gradation of the weighted average value EM (the weighted average value EM when the pixel at each pixel position i is the target pixel) corresponding to the image data DM of the graph 210d. The determination additional weight average unit 10 outputs the weighted average value EM to the data addition unit 11. The data adding unit 11 adds the image data DS shown in the graph 210d and the weighted average value EM shown in the graph 210e, and outputs the image data DO shown in the graph 210f. As described above, in the present embodiment, the ε filter includes the ε selection unit 29 and outputs a threshold value corresponding to the image data DS after gradation conversion, so that the gradation jump becomes large due to the gradation conversion. Even in such a case, it is possible to increase the effective number of gradations in a region where the gradation change is gradual.

  Next, an analog image signal SA (hereinafter referred to as a sudden change in gradation) in which the gradation changes sharply and greatly in the image display device 101 as in the graph 209a of FIG. The operation of the image display apparatus 101 when an analog image signal for conversion jump is input) will be described.

  FIG. 19 is a diagram for explaining an operation when an analog image signal that undergoes a conversion jump with a sudden change in gradation is input to the image display apparatus according to the first embodiment. In the graphs 211a to 211f shown in FIG. 19, the horizontal axis indicates the pixel position i, and the vertical axis indicates the gradation.

  A graph 211a indicates the gradation of the analog image signal SA (analog image signal that undergoes conversion jump with a sudden change), a graph 211b indicates the gradation of the n-bit image data DI, and a graph 211c indicates an (n + α) -bit image. Data DJ is shown. The graph 211d shows the gradation of the (n + α) -bit image data DS and the image data DM, the graph 211e shows the gradation of the weighted average value EM, and the graph 211f shows the gradation of the (n + α) -bit image data DO. Is shown.

  An analog image signal SA as shown in the graph 211a is input from the input terminal 1 to the receiving unit 2 to the image display device 100. The receiving unit 2 converts the analog image signal SA into digital image data DI (n bits) (binary gradations (X ′ and X ′ + 2)) as shown in the graph 211b, and the original data bit extension unit 5 is output. The gradation X ′ and gradation (X ′ + 2) here are gradations different from the gradation X and gradation (X + 2), and the gradation jump becomes large when gradation conversion is performed. Key.

  The original data bit extension unit 5 converts the gradation X ′ of the image data DI of the graph 211b into gradation 4X ′, converts the gradation (X ′ + 2) into gradation 4 (X ′ + 2), and displays the graph 211c. The image data DJ as shown in FIG.

  Here, the gradation converting unit 28 performs gradation conversion from gradation 4X ′ to gradation 4Z, gradation conversion from gradation 4 (X ′ + 2) to gradation 4 (Z + 4), and graph 211d. Image data DS as shown is output to the one-dimensional fourth-order ε filter unit 61.

  FIG. 20 is a diagram illustrating data generated by the image display apparatus according to the first embodiment when an analog image signal that undergoes a conversion jump at a sudden change in gradation is input. In FIG. 20, when the pixel at the pixel position ic in the graph 211d is the pixel of interest P (c), the image data DM (k) and the difference data ED (k) generated based on the image data DM (k) , Determination data EE (k), f {ED (k)}, weighted average value EM, and threshold data TH (k) are shown.

  The data storage unit 7 sets DM (l2) = 4Z, DM (l1) = 4Z, DM (c) = 4Z, DM (r1) = 4Z + 16 to the first difference calculation unit 8-1 to fourth difference calculation, respectively. Output to section 8-4.

  The first difference calculation unit 8-1 outputs ED (l2) = DM (l2) -DM (c) = 4Z-4Z = 0, and the second difference calculation unit 8-2 outputs ED (l1). = DM (l1) -DM (c) = 4Z-4Z = 0 is output, and the third difference calculation unit 8-3 outputs ED (c) = DM (c) -DM (c) = 4Z-4Z = 0 is output, and the fourth difference calculation unit 8-4 outputs ED (r1) = DM (r1) -DM (c) = (4Z + 16) -4Z = 16. Accordingly, “0” is input to the first ε determination unit 9-1 to the third ε determination unit 9-3, and “16” is input to the fourth ε determination unit 9-4.

  The ε selection unit 29 is set to output all threshold data TH (l2) to TH (r1) as “8” when the image data DS is near 4Z. Therefore, in the case of image data DS = 4Z or image data DS = 4Z + 16, threshold data TH (l2) = 8, threshold data TH (l1) = 8, threshold data TH (c) = 8, threshold data TH (r1) = 8 are input to the first ε determination unit 9-1 to the fourth ε determination unit 9-4, respectively. Since the difference data ED (l2) to ED (r1) is equal to or less than the respective threshold data TH (l2) to TH (r1), the determination data EE (l2) to EE (c) is “1”, and ED (r1) Is larger than the threshold data TH (r1), the determination data EE (r1) is “0”.

When the determination data EE (k) is “1”, the determination additional weight average unit 10 multiplies and adds the difference data ED (k) to the coefficient _ak , and the determination data EE (k) is “0”. Is not added. When all of the coefficients a _k (= a _l2, a _l1 , a _c , a _r1 ) are set to 0.25, the output (weighted average value EM) of the determination additional weight average unit 10 in the example shown in FIG. It is given by the following equation (8).
EM
= A _l2 × ED (l2) + a _l1 × ED (l1) + a _c ED (c)
= (0.25 × 0) + (0.25 × 0) + (0.25 × 0)
= 0
... (8)

  In the image display device 100, the above processing is performed on the image data DS supplied from the original data bit expansion unit 5 with each pixel as a target pixel in order, and the same calculation as Expression (8) is performed.

  The graph 211e indicates the gradation of the weighted average value EM (the weighted average value EM when the pixel at each pixel position i is the target pixel) corresponding to the image data DM of the graph 211d. The determination additional weight average unit 10 outputs the weighted average value EM to the data addition unit 11. The data adding unit 11 adds the image data DS shown in the graph 211d and the weighted average value EM shown in the graph 211e, and outputs the image data DO shown in the graph 211f.

  As shown in the graph 211f, the image data DO has a steep change similarly to the input (analog image signal SA) or the image data DI. In this way, the ε filter can maintain the sharpness of a region that changes drastically when the change in gradation is large. As described above, in the present embodiment, since the ε filter includes the ε selection unit 29, even if an analog image signal that undergoes a conversion jump with a sudden change in gradation is input, the input gradation depends on the input gradation. It is possible to change the size of the held edge.

  FIG. 21 is a flowchart showing a processing procedure of the image display apparatus according to the present embodiment described above. First, when the analog image signal SA is input to the input terminal 1, the receiving unit 2 receives the analog image signal SA and outputs n-bit image data DI (step ST1).

  The image data DI output from the receiving unit 2 is input to the original data bit extending unit 5 of the multi-gradation processing unit 3. The original data bit extension unit 5 extends the image data DI by α bits and outputs (n + α) -bit image data DJ (step ST2).

  The image data DJ output from the original data bit expansion unit 5 is input to the gradation conversion unit 28. The gradation converter 28 performs gradation conversion on the image data DJ and outputs (n + α) -bit image data DS (step ST3).

  The ε selector 29 receives (n + α) -bit image data DS. The ε selection unit 29 selects (ε selects) threshold data TH (1) to TH (m) corresponding to the image data DS and outputs them (step ST4). The one-dimensional m-th order ε filter unit 60 receives (n + α) -bit image data DS and threshold data TH (1) to TH (m). The one-dimensional mth-order ε filter unit 60 increases the number of gradations in the slowly changing region and outputs the image data DO (step ST5). The image data DO is input to the display unit 4. The display unit 4 displays an image based on the image data DO (step ST6).

  The effect of the present embodiment will be described with reference to FIGS. FIG. 22 is a diagram for explaining gamma conversion processing by the gradation conversion unit. The graph 212a is a diagram showing the relationship between the gradation X before gradation conversion and the gradation X 'after gradation conversion. A graph 212b is a diagram showing a relationship between a gradation X before gamma conversion and a gradation X ′ after gamma conversion in a region where the gradation changes gently (gradation X2). It is a figure which shows the relationship between the gradation X before the gamma conversion of the area | region (gradation X1) where the gradation changes rapidly, and the gradation X 'after the gamma conversion.

  As shown in the graph 212b of FIG. 22, the gradation converting unit 28 converts the gradations 4 (X2) to 4 (X2 + 4) to the gradation 4 (X2 ′) for the gradation X2 that changes gradually. ) To 4 (X2 ′ + 2).

  On the other hand, as shown in the graph 212c of FIG. 22, the gradation converting unit 28 converts gradations 4 (X1) to 4 (X1 + 1) to gradation 4 (for gradation X1 that undergoes a sharp gradation change. X1 ′) to 4 (X1 ′ + 2) are subjected to gamma conversion.

  Assume that the gradation conversion unit 28 performs gamma conversion as shown in FIG. In this case, when the signal (image data DJ) shown in the graph 213a of FIG. 23 is input to the gradation conversion unit 28, the image data DS shown in the graph 213b of FIG. . 24, when the signal (image data DJ) shown in the graph 214a in FIG. 24 is input to the gradation converting unit 28, the image data DS shown in the graph 212b in FIG.

  The graph 213b in FIG. 23 and the graph 214b in FIG. 24 are gradation jumps having the same gradation difference, but in the graph 213a in FIG. 23, the gradation change is gentle before gradation conversion, and in the graph 214a in FIG. Before gradation conversion, there is a steep gradation change. For this reason, it is desirable to interpolate gradation jumps for gradual gradation changes (in the case of FIG. 23). On the other hand, it is desirable to maintain a steep gradation change with respect to a steep gradation change (in the case of FIG. 24). In this embodiment, the ε selection unit 29 is set to output a threshold value 8 for an input gradation near the gradation 4 (X1 ′), and for an input gradation near the gradation 4 (X2 ′). The threshold value 4 is set so that the expected operation (interpolation of a gradation jump for a gradual gradation change and an operation for maintaining a gradation change for a steep gradation change). It can be performed. Although the gradation conversion unit 28 has been described as gamma conversion here, the present embodiment is not limited to these operations. Other gradation conversions such as contrast correction may be used.

  As a result, in this embodiment, even if the gradation increased due to bit expansion changes due to gradation conversion such as gamma conversion, it can be treated as small amplitude noise, while maintaining a sharp change in the image such as the contour. The number of effective gradations can be increased.

  As described above, the ε selection unit 29 can increase the number of effective gradations by setting the threshold value to a value in which the gradation increased by the bit expansion is changed by the gradation conversion. Furthermore, if a larger threshold value is set, a gradation difference greater than or equal to the gradation increased by bit expansion can be smoothed, so that an effect of noise removal can be obtained.

  When α = 0, that is, when bit extension is not used (excluded), it operates as a smoothing filter having different edges to be held depending on the gradation of the input image, and an effect of noise removal can be obtained. For example, if the threshold control unit is set to increase the threshold when the gradation is low, noise can be removed more strongly in the region with a low gradation level than in other regions. That is, the filter can be used as a filter capable of controlling the intensity of the noise removal effect according to the input gradation level.

  FIG. 25 is a diagram illustrating another configuration example (1) of the image display device according to the first embodiment. 25, the same number is attached | subjected about the component which achieves the same function as the image display apparatus 101 shown in FIG. 1, and the overlapping description is abbreviate | omitted.

  In the image display device 102, the gradation conversion unit 28 is in the preceding stage of the original data bit expansion unit 5. When the analog image signal SA is input to the input terminal 1, the receiving unit 2 receives the analog image signal SA and inputs n-bit image data DI to the gradation converting unit 28.

  The gradation conversion unit 28 performs gradation conversion on the image data DI and inputs n-bit image data DJ to the original data bit expansion unit 5. The original data bit extension unit 5 extends the image data DJ by α bits and outputs (n + α) -bit image data DS. Then, the image data DJ output from the original data bit expansion unit 5 is input to the gradation conversion unit 28 and the one-dimensional m-order ε filter unit 60.

  In the image display device 102, if the ε selection unit 29 sets a threshold value in accordance with the characteristics of gradation conversion, the level of an area where gradation gradually changes without reducing image sharpness (abrupt change in signal). It is possible to increase the logarithm.

  The operation and effect of the image display apparatus 102 will be described with reference to FIGS. FIG. 26 is a diagram for explaining the gamma conversion processing by the gradation conversion unit. A graph 215a is a diagram illustrating a relationship between the gradation X before gradation conversion and the gradation X ′ after gradation conversion. The graph 215b is a diagram showing the relationship between the gradation X before gamma conversion and the gradation X ′ after gamma conversion in the area where the gradation changes gently (gradation X2). The graph 215c It is a figure which shows the relationship between the gradation X before the gamma conversion of the area | region (gradation X1) where the gradation changes rapidly, and the gradation X 'after the gamma conversion.

  As shown in the graph 215b of FIG. 26, the gradation converting unit 28 converts the gradations (X2) to (X2 + 4) from the gradations (X2 ′) to (X2) for the gradation X2 that undergoes a gradual gradation change. X2 ′ + 2).

  On the other hand, as shown in the graph 215c of FIG. 26, the gradation converting unit 28 converts the gradations (X1) to (X1 + 3) to the gradation (X1 ′) for the gradation X1 that undergoes a sharp gradation change. Convert to ~ (X1 '+ 6).

  It is assumed that the gradation conversion unit 28 performs gamma conversion as shown in FIG. In this case, when the signal (image data DI) shown in the graph 216a in FIG. 27 is input to the gradation conversion unit 28, the image data DJ shown in the graph 216b in FIG. . The image data DJ is converted by the original data bit expansion unit 5 as image data DS shown in the graph 216c.

  When the signal (image data DI) shown in the graph 217a in FIG. 28 is input to the gradation conversion unit 28, the gradation conversion unit 28 outputs the image data DJ shown in the graph 217b in FIG. The image data DJ is converted by the original data bit expansion unit 5 as image data DS shown in the graph 217c.

  The graph 216b in FIG. 27 and the graph 217b in FIG. 28 are gradation jumps having the same gradation difference, but in the graph 216a in FIG. 27, the gradation change is gentle before gradation conversion, and in the graph 217a in FIG. Before gradation conversion, there is a steep gradation change. For this reason, it is desirable to interpolate a jump in gradation for a gradual gradation change (in the case of FIG. 27). On the other hand, it is desirable to maintain a steep gradation change with respect to a steep gradation change (in the case of FIG. 28).

  In the image display apparatus 102, the ε selection unit 29 is set to output the threshold value 8 for the input gradation near the gradation X1 ′, and outputs the threshold value 4 for the input gradation near the gradation X2 ′. If set, the expected operation can be performed.

  Thus, in the image display apparatus 102, even if a signal changed by gradation conversion such as gamma conversion is input to the multi-gradation processing unit 3, it can be treated as small amplitude noise, and the image such as the contour is steep. The effective number of gradations can be increased while maintaining the change.

  FIG. 29 is a diagram illustrating another configuration example (2) of the image display device according to the first embodiment. 29, the same number is attached | subjected about the component which achieves the same function as the image display apparatus 101 shown in FIG. 1, and the overlapping description is abbreviate | omitted.

  In the image display device 103, the gradation converting unit 28 (not shown in FIG. 29) is in front of the receiving unit 2. As a result, in the image display apparatus 103, data that has been subjected to gradation conversion in advance is input to the receiving unit 2. When the analog image signal SA subjected to gradation conversion is input to the input terminal 1, the receiving unit 2 receives the analog image signal SA and inputs n-bit image data DI to the original data bit extending unit 5. .

  The original data bit extension unit 5 extends the image data DI by α bits and outputs (n + α) -bit image data DS. The image data DJ output from the original data bit expansion unit 5 is input to the ε selection unit 29 and the one-dimensional m-order ε filter unit 60.

  Similarly to the image display device 101 shown in FIG. 1 and the image display device 102 shown in FIG. 25, the image display device 103 can set the threshold value according to the characteristics of gradation conversion without reducing the sharpness of the image. It is possible to increase the number of gradations in a region where the tone gradually changes.

  FIG. 30 is a diagram illustrating another configuration example (3) of the image display device according to the first embodiment. Of the constituent elements in FIG. 30, constituent elements that achieve the same functions as those of the image display apparatus 102 shown in FIG. 25 are assigned the same reference numerals, and redundant descriptions are omitted.

  Compared with the image display device 102 shown in FIG. 25, the image display device 104 is not provided with the original data bit expansion unit 5, and the one-dimensional m-order ε filter unit 60 is included in the multi-gradation processing unit 3. Instead, a one-dimensional mth-order ε filter unit 27 with bit extension is provided. The one-dimensional m-th order ε filter unit 27 with bit extension is provided with a determination additional weight average unit 32 and a data addition unit 33 instead of the determination additional weight average unit 10 and the data addition unit 11.

  The one-dimensional m-order ε filter unit 27 with bit expansion is a means in which a function for performing bit expansion ε during calculation of the ε filter is added to the one-dimensional m-order ε filter unit 60. The determination additional weighted average unit 32 performs weighted average calculation and bit extension based on the determination data EE and the difference data ED, and outputs a weighted average value EM that is bit-extended by α bits. In the image display device 104, for example, bit expansion is performed by generating average data EM using a numerical value of the decimal places that appears when the arithmetic operation of the determination additional weighted average is performed as in the example of FIG. be able to. In the data adding unit 33, the input image data DM (c) is bit-expanded to (n + α) bits and added, and output to the display unit 4 as image data DO.

  Thus, in the image display device 104, bit expansion is not performed before the ε filter, but is performed during the calculation of the ε filter. With the configuration described above, the same effects as those of the image display apparatus 102 shown in FIG. 25 can be obtained.

  In the image display device 100 shown in FIG. 1, the case where the ε filter is a one-dimensional ε filter has been described, but the present embodiment is not limited to the one-dimensional ε filter. FIG. 31 and FIG. 32 are diagrams showing a configuration of an image display device including a two-dimensional ε filter that the ε filter processes in the horizontal direction and the vertical direction. 31 and 32, the same numbers are assigned to the components that achieve the same functions as those of the image display device 100 shown in FIG.

  The image display device 105 shown in FIG. 31 includes a two-dimensional m-order ε filter unit 62 instead of the one-dimensional m-order ε filter unit 60 as an ε filter. Similar to the one-dimensional m-order ε filter unit 60, the two-dimensional m-order ε filter unit 62 is connected to the gradation conversion unit 28, the ε selection unit 29, and the display unit 4.

  The two-dimensional m-th order ε filter unit 62 performs processing (ε filtering processing) on a two-dimensional region of horizontal pixels (h) × vertical pixels (v). That is, the two-dimensional m-th order ε filter unit 62 stores a sharp change in gradation based on data of pixels arranged in a two-dimensional direction (vertical direction, horizontal direction) with the pixel of interest at the center, It is used as an edge-preserving smoothing filter that performs smoothing by treating small amplitude components as noise.

  31 includes a data storage unit 34, a first difference calculation unit 8-1 to an m-th difference calculation unit 8-m, and a first ε determination unit 9-1 to the first. An ε determination unit 9-m for m, a determination additional weighted average unit 10, and a data addition unit 11 are provided, and have a role of increasing the effective number of gradations for the image data DS.

  The data storage unit 34 stores the image data DS from the gradation conversion unit 28, and also stores the image data DM (1) to the first difference calculation unit 8-1 to the m-th difference calculation unit 8-m, respectively. Output DM (m). Further, the data storage unit 34 outputs the image data DM (c) to the first difference calculation unit 8-1 to the m-th difference calculation unit 8-m and the data addition unit 11.

  Each of the image data DM (1) to DM (m) of the present embodiment has image data of image data of pixels that are separated from the target pixel c in the vertical and horizontal directions by a predetermined number of pixels (coordinate values). .

  Image data DM (1) to DM (m) in the vertical and horizontal directions are input from the data storage unit 34 to the first difference calculation unit 8-1 to the m-th difference calculation unit 8-m, respectively. Further, the image data DM (c) is input from the data storage unit 34 to the data addition unit 11.

  The first difference calculation unit 8-1 to m-th difference calculation unit 8-m calculate the difference between the image data DM (1) to DM (m) in the vertical and horizontal directions and the image data DM (c), respectively. The difference data is calculated as ED (1) to ED (m). The first difference calculation unit 8-1 to the m-th difference calculation unit 8-m respectively send the difference data ED in the vertical and horizontal directions to the first ε determination unit 9-1 to the m-th ε determination unit 9-m. (1) to ED (m) are output.

  Based on the image data DS (1) to DS (m) from the gradation conversion unit 28, the ε selection unit 29 uses the vertical and horizontal threshold data TH (1) to TH (m) as the first ε determination. Input to the unit 9-1 to the m-th ε determination unit 9-m.

  The first ε determination unit 9-1 to the m-th ε determination unit 9-m determine whether or not the difference data ED (1) to ED (m) is larger than the threshold data TH (1) to TH (m). Make a decision. The first ε determination unit 9-1 to the m-th ε determination unit 9-m output the determination results to the determination additional weight average unit 10 as determination data EE (1) to EE (m).

  The determination additional weight average unit 10 performs weighted average of the difference data ED (1) to ED (m) based on the determination data EE (1) to EE (m), and the weighted average value obtained as a result thereof is weighted average value. (Average data) Output to the data adder 11 as EM.

  The data adding unit 11 adds the image data DS to the weighted average values EM (1) to EM (m).

  The image data whose effective number of gradations has been increased by the one-dimensional mth-order ε filter unit 60 is output from the data adding unit 11 to the display unit 4 as image data DO.

  32 includes a one-dimensional vth-order vertical ε filter unit 63a and a one-dimensional h-order horizontal ε filter unit 63b as ε filters. In the image display device 106, the gradation conversion unit 28 includes a one-dimensional v-th order vertical ε filter unit 63a, a one-dimensional h-th order horizontal ε filter unit 63b, a first ε selection unit 29-1, and a second ε selection unit 29-. 2 is connected. The one-dimensional v-th order vertical ε filter unit 63 a is connected to the one-dimensional h-th order horizontal ε filter unit 63 b, and the one-dimensional h-order horizontal ε filter unit 63 b is connected to the display unit 4.

  The one-dimensional v-th order vertical ε filter unit 63 a includes a V data storage unit (vertical direction data storage unit) 15, a first V difference calculation unit (vertical direction difference calculation unit) 16-1 to a vth V difference calculation unit 16. -V, first Vε determination unit (vertical direction ε determination unit) 17-1 to vth Vε determination unit 17-v, V determination additional weight average unit (vertical direction determination additional weight average unit) 18, and V data An adder (vertical adder) 19 is provided.

  The one-dimensional v-th order vertical ε filter unit 63a performs processing in the vertical direction of the image on the (n + α) -bit original data. The one-dimensional v-th order vertical ε filter unit 63a is based on the pixel data aligned in the vertical direction with respect to the target pixel, and stores an abrupt change while smoothing by treating a small amplitude component as noise. It is used as a mold smoothing filter. The one-dimensional v-th order vertical ε filter unit 63a converts the image data (image data VDO described later) having an increased effective number of gradations with respect to the vertical gradation change of the image data DS into a one-dimensional h-order horizontal ε filter. To the unit 63b.

  The difference between the one-dimensional v-th order vertical ε filter unit 63a and the one-dimensional m-th order ε filter unit 60 is that the one-dimensional m-th order ε filter unit 60 increases the effective number of gradations for the image data DS in the horizontal direction. On the other hand, the one-dimensional v-th order vertical ε filter unit 63a increases the effective number of gradations for the image data DS in the vertical direction.

  Therefore, the V data storage unit 15, the first V difference calculation unit 16-1 to the vth V difference calculation unit 16-v, and the first Vε determination unit 17-1 to 17-1 of the one-dimensional vth-order vertical ε filter unit 63a. The vth Vε determination unit 17-v, the V determination additional weighted average unit 18, and the V data addition unit 19 are respectively a data storage unit 7 and a first difference calculation unit 8-1 of the one-dimensional mth-order ε filter unit 60. To m-th difference calculation unit 8-m, first ε determination unit 9-1 to m-th ε determination unit 9-m, determination additional weight average unit 10, and data addition unit 11.

  In other words, each component of the one-dimensional v-th order vertical ε filter unit 63a and each component of the one-dimensional m-th order ε filter unit 60 is the image data DS in the vertical direction or the image data in the horizontal direction. Except for the difference in DS, almost the same processing is performed. The first ε selection unit 29-1 corresponds to the ε selection unit 29 and performs substantially the same processing as the ε selection unit 29.

  In addition, the image data VDM, difference data VED, determination data VEE, threshold data VTH, weighted average value VEM, and image data VDO generated by the one-dimensional vth-order vertical ε filter unit 63a are each a one-dimensional mth-order ε filter unit 60. Corresponds to the image data DM, difference data ED, determination data EE, threshold data TH, weighted average value EM, and image data DO.

  Here, each component provided in the one-dimensional v-th order vertical ε filter unit 63a will be described in detail. The V data storage unit 15 stores the image data DS from the gradation conversion unit 28, and each of the first V difference calculation unit 16-1 to the vth V difference calculation unit 16-v receives image data VDM ( 1) to VDM (v) are output. Further, the V data storage unit 15 outputs the image data VDM (c) to the first V difference calculation unit 16-1 to the vth difference calculation unit 16-v and the V data addition unit 19.

  The image data VDM (c) is image data when the target pixel is the target pixel c. Each of the image data VDM (1) to VDM (v) is image data of pixels that are separated upward or downward by a predetermined number of pixels from the target pixel c. For example, when m = 5, if the image data VDM (3) is the image data VDM (c), the image data VDM (1) becomes the image data of the pixel two previous (upper) of the pixel of interest c, and the image data The data VDM (2) is the image data of the pixel immediately before (upper side) the pixel of interest c, and the image data VDM (4) is the image data of the pixel after the pixel of interest c (lower side). VDM (5) is the image data of the pixel after (lower) the pixel of interest c.

  The first difference calculation unit 16-1 to the v-th difference calculation unit 16-v respectively calculate the difference between the image data VDM (1) to VDM (v) and the image data VDM (c) as difference data VED (1 ) To VED (v). The first difference calculation unit 16-1 to the v-th difference calculation unit 16-v respectively send the difference data VED (1) to the first ε determination unit 17-1 to the v-th ε determination unit 17-v. VED (v) is output.

  The first ε determination unit 17-1 to the v-th ε determination unit 17-v are the difference data VED (1) to VED (1) to 1-v from the first difference calculation unit 16-1 to the v-th difference calculation unit 16-v, respectively. It is determined whether VED (v) is larger than the threshold data VTH (1) to VTH (v) from the first ε selection unit 29-1, and the determination result is determined as determination data VEE (1) to VEE ( v) is output to the V determination additional weight average unit 18.

  The V determination additional weight average unit 18 performs weighted averaging of the difference data VED (1) to VED (v) based on the determination data VEE (1) to VEE (v), and the weighted average value obtained as a result is weighted average The values VEM (1) to VEM (v) are output to the V data adding unit 19. The V data adding unit 19 adds the image data VDM (c) to the weighted average values VEM (1) to VEM (v).

  The image data in which the effective number of gradations is increased by the one-dimensional v-th order ε filter unit 63a is converted into image data VDO (1) to VDO (v) from the V-data adder unit 19 as a one-dimensional h-order vertical ε filter unit 63b. Is output.

  The one-dimensional h-order horizontal ε filter unit 63b includes an original data storage unit 20, a first original data difference calculation unit 21-1 to an hth original data difference calculation unit 21-h, a first Hε determination unit ( (Horizontal direction ε determination unit) 22-1 to h-th Hε determination unit 22-h, H data storage unit (horizontal direction data storage unit) 23, first H difference calculation unit (horizontal direction difference calculation unit) 24-1 To an h-th H difference calculation unit 24-h, an H determination additional weight average unit (horizontal direction determination additional weight average unit) 25, and an H data addition unit (horizontal direction data addition unit) 26.

  The original data storage unit 20 is connected to the first original data difference calculation unit 21-1 to the h-th original data difference calculation unit 21-h, and the first original data difference calculation unit 21-1 to the h-th original data. The data difference calculation unit 21-h is connected to the first Hε determination unit 22-1 to the hth Hε determination unit 22-h. Further, the first Hε determination unit 22-1 to the hth Hε determination unit 22-h are connected to the second ε selection unit 29-2.

  The H data storage unit 23 is connected to the first H difference calculation unit 24-1 to the h-th H difference calculation unit 24-h. Further, the H determination additional weight average unit 25 includes a first H difference calculation unit 24-1 to an hth H difference calculation unit 24-h, a first Hε determination unit 22-1 to an hth Hε determination unit 22. -H, H is connected to the data adder 26.

  The one-dimensional h-order horizontal ε filter unit 63b performs processing in the horizontal direction of the image on the (n + α) -bit data output from the one-dimensional v-th order vertical ε filter unit 63a. The one-dimensional h-th order horizontal ε filter unit 63b is based on the pixel data aligned in the horizontal direction with respect to the target pixel, and stores an abrupt change while smoothing by treating a small amplitude component as noise. It is used as a mold smoothing filter. The one-dimensional h-order horizontal ε filter unit 63b has a role of increasing the effective number of gradations of the image data VDO based on a change in gradation in the horizontal direction of the image data DS.

  The difference between the one-dimensional h-order horizontal ε filter unit 63b and the one-dimensional m-order ε filter unit 60 is that the one-dimensional m-order ε filter unit 60 uses the determination data EE in the horizontal direction and the difference data ED in the horizontal direction to obtain a weighted average value. In contrast to the calculation of EM, the one-dimensional h-th order horizontal ε filter unit 63b calculates the weighted average value EM using the determination data HEE in the horizontal direction and the difference data HED in the horizontal direction.

  Therefore, the original data storage unit 20, the first original data difference calculation unit 21-1 to the h-th original data difference calculation unit 21-h, the first Hε determination unit 22- of the one-dimensional h-order horizontal ε filter unit 63b. The 1st to h-th Hε determination units 22-h include a data storage unit 7, a first difference calculation unit 8-1 to an m-th difference calculation unit 8-m, and a first one of the one-dimensional m-th order ε filter unit 60, respectively. The ε determination unit 9-1 to the m-th ε determination unit 9-m perform substantially the same processing. Further, the H data storage unit 23, the first H difference calculation unit 24-1 to the hth H difference calculation unit 24-h, the H determination additional weight average unit 25, and the H of the one-dimensional h-order horizontal ε filter unit 63b. The data addition unit 26 includes a data storage unit 7, a first difference calculation unit 8-1 to an m-th difference calculation unit 8-m, a determination addition weighted average unit 10, and a data addition of the one-dimensional m-order ε filter unit 60. Corresponding to the part 11, substantially the same processing is performed. The second ε selection unit 29-2 corresponds to the ε selection unit 29 and performs substantially the same processing as the ε selection unit 29.

  Further, the image data HDM, the difference data HED, the determination data HEE, the threshold data HTH, and the weighted average value HEM generated by the one-dimensional h-order horizontal ε filter unit 63b are respectively generated by the one-dimensional m-order ε filter unit 60. It corresponds to image data DM, difference data ED, determination data EE, threshold data TH, and weighted average value EM. The image data BDM and difference data BED generated by the one-dimensional h-order horizontal ε filter unit 63b correspond to the image data DM and difference data ED generated by the one-dimensional m-order ε filter unit 60, respectively.

  Here, each component provided in the one-dimensional h-order horizontal ε filter unit 63b will be described in detail. The H data storage unit 23 stores the image data VDO from the V data addition unit 19, and each of the first H difference calculation unit 24-1 to the hth H difference calculation unit 24-h has image data HDM ( 1) to output HDM (h). The H data storage unit 23 outputs the image data HDM (c) to the first H difference calculation unit 24-1 to the hth difference calculation unit 24-h and the H data addition unit 26.

  The image data HDM (c) is image data when the target pixel is the target pixel c. Each of the image data HDM (1) to HDM (h) is image data of pixels that are separated upward or downward from the target pixel c by a predetermined number of pixels.

  The first difference calculation unit 24-1 to the h-th difference calculation unit 24-h calculate the difference between the image data HDM (1) to HDM (h) and the image data HDM (c), respectively, as difference data HED (1 ) To HED (h). The first H difference calculation unit 24-1 to the h-th H difference calculation unit 24-h output the difference data HED (1) to HED (h) to the H determination additional weight average unit 25.

  Further, the original data storage unit 20 stores the image data DS from the gradation conversion unit 28, and the first data difference calculation unit 21-1 to the h-th original data difference calculation unit 21-h respectively. Image data BDM (1) to BDM (h) are output. The original data storage unit 20 outputs the first original data difference calculation unit 21-1 to the h-th original data difference calculation unit 21-h image data BDM (c).

  The image data BDM (c) is image data when the target pixel is the target pixel c. The image data BDM (1) to BDM (h) are image data of pixels that are separated from the target pixel c in the right or left direction by a predetermined number of pixels.

  The first original data difference calculation unit 21-1 to the h-th original data difference calculation unit 21-h are configured to calculate differences between the image data BDM (1) to BDM (h) and the image data BDM (c), respectively. Data BED (1) to BED (h) are calculated. The first original data difference calculation unit 21-1 to the h-th original data difference calculation unit 21-h respectively send the difference data BED to the first Hε determination unit 22-1 to the h-th Hε determination unit 22-h. (1) to BED (h) are output.

  The first Hε determination unit 22-1 to the hth Hε determination unit 22-h are the difference data BED from the first original data difference calculation unit 21-1 to the hth original data difference calculation unit 21-h, respectively. It is determined whether (1) to BED (h) are larger than the threshold data HTH (1) to HTH (h) from the second ε selection unit 29-2, and the determination result is determined as determination data HEE (1 ) To HEE (h) are output to the H determination additional weight average unit 25.

  The H determination additional weight average unit 25 performs weighted averaging of the difference data HED (1) to HED (h) based on the determination data HEE (1) to HEE (h), and the weighted average value obtained as a result is weighted average The values HEM (1) to HEM (h) are output to the H data adding unit 26. The H data adding unit 26 adds the image data HDM (c) to the weighted average values HEM (1) to HEM (h). Image data whose effective number of gradations has been increased by the one-dimensional h-order ε filter unit 63b is output from the H data addition unit 26 to the display unit 4 as image data DO (1) to DO (h).

  An ε fill unit that performs the two-dimensional processing as described above, and a threshold control unit that changes the threshold ε according to the input gradation (first ε selection unit 29-1 and second ε selection unit 29-2). Therefore, the size of the edge to be held for each gradation can be set both in the vertical direction and in the horizontal direction.

  Here, although the one-dimensional h-th order horizontal ε filter unit 63b calculates the weighted average value HEM using the horizontal determination data HEE and the vertical difference data HED, the vertical determination data and the horizontal difference data are calculated. The weighted average value EM may be calculated using Further, the one-dimensional h-order horizontal ε filter unit 63b may calculate the weighted average value EM using the vertical determination data EE and the vertical difference data ED.

  In the present embodiment, the ε selection unit 29, the one-dimensional m-order ε filter unit 60, the one-dimensional fourth-order ε filter unit 61, the two-dimensional m-order ε filter unit 62, the one-dimensional v-order vertical ε filter unit 63a, Although the one-dimensional h-order horizontal ε filter unit 63b is configured separately, the one-dimensional m-order ε filter unit 60, the one-dimensional fourth-order ε filter unit 61, the two-dimensional m-order ε filter unit 62, the one-dimensional v-th order vertical The ε filter unit 63 a and the one-dimensional h-order horizontal ε filter unit 63 b may include the ε selection unit 29.

  As described above, according to the first embodiment, since the gradation increased by the bit extension is smoothed using the ε filter, the sharpness of an image having a region where the gradation such as the outline changes sharply is impaired. Without increasing the number of gradations of the image data. Therefore, it is possible to eliminate the pseudo contour caused by the missing image level and reduce the image quality deterioration due to the pseudo contour.

  Further, since the threshold data TH corresponding to the image data is selected from the stored threshold value table and used, it is possible to easily determine whether or not the difference data ED is larger than the threshold data TH.

  Further, since the gradation conversion of the image data DJ is performed and the gradation of the gradation-converted image data DS is smoothed, it is possible to perform smoothing processing and display processing of the image data having a good appearance. .

  Further, since the threshold value of the ε filter is changed according to the gradation of the image data DS, it becomes possible to reduce the pseudo contour while maintaining the sharpness of the image. Further, since the threshold value corresponding to the image data DS is determined based on the table indicating the threshold value for each image data DS (gradation DS), the threshold value of the ε filter can be easily determined.

  In addition, since the original data bit expansion unit 5 is arranged before the ε filter such as the one-dimensional m-order ε filter unit 60, the bit expansion of the image data is performed by the ε filter such as the one-dimensional m-order ε filter unit 60. There is no need to do it. Therefore, it is possible to smooth the predetermined gradation of the image data bit-extended with a simple configuration. Further, since the threshold value of the ε filter can be determined based on the bit-expanded image data, it is possible to easily select an appropriate threshold value of the ε filter. This makes it possible to reduce the pseudo contour while maintaining the sharpness of the image.

  Further, since the image display device 104 includes the one-dimensional m-th order ε filter unit 27 with bit extension, it is possible to perform bit extension after smoothing the gradation of the image data. Therefore, as in the case where the original data bit expansion unit 5 is arranged before the ε filter, it is possible to reduce the pseudo contour while maintaining the sharpness of the image.

Embodiment 2. FIG.
Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, a threshold value ε corresponding to the input gradation is calculated, and the difference data ED and the threshold value data TH are compared using the calculated threshold value ε.

  FIG. 33 is a diagram showing a configuration of an image display apparatus according to Embodiment 2 of the present invention. 33, the same number is attached | subjected about the component which achieves the same function as the image display apparatus 100 of Embodiment 1 shown in FIG. 1, and the overlapping description is abbreviate | omitted.

  The image display device 110 according to the second embodiment includes an input terminal 1, a receiving unit 2, a multi-gradation processing unit 3, and a display unit 4. Among these, the receiving unit 2 and the multi-gradation processing unit 3 constitute an image processing apparatus.

  In this embodiment, as an example of the receiving unit 2, a case where the receiving unit 2 is an A / D converter that converts an analog image signal into digital image data will be described. Note that a tuner may be provided in the receiving unit 2 so that the composite signal is demodulated into a luminance or chromaticity signal inside the receiving unit 2 and then converted into digital image data. Alternatively, the receiving unit 2 may be a digital interface, and the receiving unit 2 may receive digital data from the input terminal 1 and output n (n is a natural number) bit image data DI.

  The input terminal 1 is a terminal for inputting the analog image signal SA, and outputs the input analog image signal SA to the receiving unit 2. The receiving unit 2 converts the analog image signal SA into n-bit image data DI and outputs it to the multi-gradation processing unit 3.

  The multi-gradation processing unit 3 includes an original data bit expansion unit 5, a gradation conversion unit 28, an ε calculation unit 30, and a one-dimensional m-order ε filter unit 60, and converts n-bit image data DI into (n + α ) Convert to bits and output to the display unit 4.

  The original data bit expansion unit 5 outputs (n + α) -bit image data DJ obtained by extending the n-bit image data DI by α bits to the gradation conversion unit 28. The gradation conversion unit 28 performs gradation conversion such as gamma conversion and contrast correction on the image data DJ, and the image data after gradation conversion is used as image data DS ((n + α) bits). The result is output to the one-dimensional m-order ε filter unit 60.

  Next, an example of gradation conversion by the ε calculation unit 30 will be described. The ε calculation unit 30 of the present embodiment has a threshold value table for each gradation, and interpolates and outputs the threshold value from a table corresponding to the input image data DS (gradation DS). 34 and 35 are diagrams showing the relationship between gradation and threshold. In FIGS. 34 and 35, a table showing the threshold values for each gradation is shown as a graph. For example, the ε calculating unit 30 holds threshold data TH1, TH2, TH3, TH4 corresponding to the gradations X1, X2, X3, X4 shown in the graph 220a of FIG. 34 as a threshold value table for each gradation. Suppose that

  The ε calculation unit 30 uses this table to calculate the threshold values for the remaining gradations (gradations other than the gradations X1 to X4) by linear interpolation. Thereby, the ε calculating unit 30 calculates the relationship between the gradation and the threshold shown in the graph 220b from the graph 220a. As a result, the ε calculation unit 30 is equivalent to having a graph (table) like the graph 220b.

  Further, for example, the ε calculating unit 30 uses the threshold data TH1, TH2, TH3 corresponding to the inter-gradation levels X1-X2, X2-X3, X3-X4 shown in the graph 221a of FIG. 35 as a threshold value table for each gradation. Suppose you hold it.

  The ε calculating unit 30 uses this table to calculate the vicinity of a break between gradations by linear interpolation. Thereby, the ε calculation unit 30 calculates the relationship between the gradation and the threshold value shown in the graph 221a to the graph 221b. As a result, the ε calculation unit 30 is equivalent to having a graph (table) like the graph 221b.

  As described above, if the threshold value is calculated by the interpolation calculation, it is not necessary to store the threshold values corresponding to all the gradations unlike the ε selection unit 29 of the first embodiment. Here, as an example of the operation of the ε calculation unit 30, the processing shown in FIG. 34 and FIG. 35 (processing for creating the graph 220b from the graph 220a and processing for creating the graph 221b from the graph 221a) is shown. However, the present invention is not limited to these operations. That is, the ε calculation unit 30 may perform an interpolation operation on the threshold value from any graph.

  The one-dimensional m-th order ε filter unit 60 is an edge that performs smoothing by treating a small amplitude component as noise while preserving a steep change based on data of pixels aligned in a one-dimensional direction with respect to the target pixel. Used as a conservative smoothing filter (ε filter). The one-dimensional m-th order ε filter unit 60 smoothes the gradation increased by the original data bit expansion unit 5 to eliminate the gradation jump and increase the effective number of gradations.

  The one-dimensional m-th order ε filter unit 60 includes a data storage unit 7, a first difference calculation unit 8-1 to an m-th difference calculation unit 8-m, a first ε determination unit 9-1 to an m-th ε determination. Unit 9-m, determination additional weight average unit 10, and data addition unit 11.

  The image data whose effective number of gradations has been increased by the one-dimensional mth-order ε filter unit 60 is output from the data adding unit 11 to the display unit 4 as image data DO. The display unit 4 is a display unit such as a liquid crystal monitor that displays (n + α) -bit image data DO. The image data DO whose effective number of gradations has been increased by the one-dimensional m-th order ε filter unit 60 is output to the display unit 4. The display unit 4 displays (n + α) -bit image data DO.

In the present embodiment, the ε filter performs the ε filter processing by regarding the gradation increased by bit expansion as small amplitude noise. That is, when bit expansion is performed from n bits to (n + α) bits, the threshold ε of the ε filter is set to 2 ^α (2 ^ α). Thus, the ε filter can increase the effective number of gradations while maintaining a sharp change in the image such as the contour. However, when gradation conversion such as gamma conversion is performed between bit expansion and ε filter processing, the size of gradation increased by bit expansion changes. Therefore, the threshold value ε is changed in accordance with the gradation conversion. That is, the edge size that can be stored in the ε filter is changed according to the input gradation.

  In the present embodiment, the image display apparatus 100 has an ε calculation unit 30 (threshold control unit) that changes the threshold ε according to an input gradation, and a one-dimensional m-order ε filter whose threshold is controlled by the ε calculation unit 30. Part 60. The calculation unit 30 is set so that the ε calculation unit 30 corresponding to the threshold control unit calculates the threshold according to the gradation conversion.

  Hereinafter, as an example of multi-gradation processing, a case where α = 2, that is, a case where an n-bit image is subjected to multi-gradation processing to n + 2 bits will be described. FIG. 36 is a diagram illustrating a configuration of the image display apparatus according to the second embodiment when m = 4. 36, the same number is attached | subjected about the component which achieves the same function as the image display apparatus 110 shown in FIG. 33, and the overlapping description is abbreviate | omitted. The image display device 111 includes a one-dimensional fourth-order ε filter unit 61 instead of the one-dimensional m-order ε filter unit 60.

  First, the operation of the image display device 110 when an analog image signal that undergoes a conversion jump at a gradual gradation is input to the image display device 110 will be described. FIG. 37 is a diagram for explaining an operation in the case where an analog image signal that undergoes a conversion jump with a gradual gradation is input to the image display device according to the second embodiment. In the graphs 222a to 222f shown in FIG. 37, the horizontal axis indicates the pixel position i, and the vertical axis indicates the gradation.

  The graph 222a shows the gradation of the analog image signal SA, the graph 222b shows the gradation of the n-bit image data DI, and the graph 222c shows the (n + α) -bit image data DJ. The graph 222d shows the gradation of the image data DS and the image data DM of (n + α) bits, the graph 222e shows the gradation of the weighted average value EM, and the graph 222f shows the gradation of the image data DO of (n + α) bits. Is shown.

  An analog image signal SA as shown in the graph 222 a is input from the input terminal 1 to the receiving unit 2 to the image display device 100. The receiving unit 2 converts the analog image signal SA into digital image data DI (n bits) (binary gradation (X and X + 1)) as shown in the graph 222 b and outputs the converted data to the original data bit expansion unit 5. To do.

  The original data bit expansion unit 5 converts the gradation X of the image data DI of the graph 222b into gradation 4X, converts the gradation (X + 1) into gradation 4 (X + 1), and produces image data as shown in the graph 222c. DJ is output to the gradation conversion unit 28.

  FIG. 38 is a diagram illustrating data generated by the image display apparatus according to the second embodiment when an analog image signal that undergoes a conversion jump at a gradual gradation is input. In FIG. 38, image data DM (k) and difference data ED (k) generated based on the image data DM (k) when the pixel at the pixel position ic in the graph 222d is the target pixel P (c). , Determination data EE (k), f {ED (k)}, weighted average value EM, and threshold data TH (k) are shown.

  The data storage unit 7 sets DM (l2) = 4Z, DM (l1) = 4Z, DM (c) = 4Z, DM (r1) = 4Z + 8, respectively, as the first difference calculation unit 8-1 to fourth difference calculation. Output to section 8-4.

  The first difference calculation unit 8-1 outputs ED (l2) = DM (l2) -DM (c) = 4Z-4Z = 0, and the second difference calculation unit 8-2 outputs ED (l1). = DM (l1) -DM (c) = 4Z-4Z = 0 is output, and the third difference calculation unit 8-3 outputs ED (c) = DM (c) -DM (c) = 4Z-4Z = 0. The fourth difference calculation unit 8-4 outputs ED (r1) = DM (r1) -DM (c) = (4Z + 8) -4Z = 8. Accordingly, “0” is input to the first ε determination unit 9-1 to the third ε determination unit 9-3, and “8” is input to the fourth ε determination unit 9-4.

  The ε calculation unit 30 is set to output all threshold data TH (l2) to TH (r1) as “8” when the image data DS is near 4Z. At this time, in the image display device 110 according to the present embodiment, the ε calculation unit 30 interpolates the threshold corresponding to the image data DS based on the threshold table for each gradation.

  When the image data DS = 4Z or 4Z + 8, the threshold data TH (l2) = 4, the threshold data TH (l1) = 4, the threshold data TH (c) = 4, and the threshold data TH (r1) = 4 are the first. The information is input to the ε determination unit 9-1 to the fourth ε determination unit 9-4. Since the difference data ED (l2) to ED (r1) is equal to or less than the respective threshold data TH (l2) to TH (r1), the determination data EE (l2) to EE (r1) is “1”.

When the determination data EE (k) is “1”, the determination additional weight average unit 10 multiplies and adds the difference data ED (k) to the coefficient _ak , and the determination data EE (k) is “0”. Is not added. When all the coefficients a _k (= a _l2, a _l1 , a _c , a _r1 ) are set to 0.25, in the example shown in FIG. 38, the output (weighted average value EM) of the determination additional weight average unit 10 is It is given by the following equation (9).
EM
= A _l2 × ED (l2) + a _l1 × ED (l1) + a _c × ED (c) + a _r1 × ED (r1) = (0.25 × 0) + (0.25 × 0) + (0.25 × 0) + (0.25 × 8)
= 2
... (9)

  In the image display apparatus 100, the above processing is performed on the image data DS supplied from the original data bit expansion unit 5 with each pixel as a target pixel in order, and the same calculation as Expression (9) is performed.

  A graph 222e indicates the gradation of the weighted average value EM (the weighted average value EM when the pixel at each pixel position i is the target pixel) corresponding to the image data DM of the graph 222d. The determination additional weight average unit 10 outputs the weighted average value EM to the data addition unit 11. The data adding unit 11 adds the image data DS shown in the graph 222d and the weighted average value EM shown in the graph 222e, and outputs the image data DO shown in the graph 222f. As described above, the image display apparatus 110 can increase the effective number of gradations in a region where the gradation change is gradual even when the gradation jump becomes large due to gradation conversion.

  Next, the operation of the image display device 110 when an analog image signal that undergoes a conversion jump with a sudden change in gradation is input to the image display device 110 will be described. FIG. 39 is a diagram for explaining an operation when an analog image signal that undergoes a conversion jump with a sudden change in gradation is input to the image display device according to the second embodiment. In the graphs 223a to 223f shown in FIG. 37, the horizontal axis indicates the pixel position i, and the vertical axis indicates the gradation.

  The graph 223a shows the gradation of the analog image signal SA, the graph 223b shows the gradation of the n-bit image data DI, and the graph 223c shows the (n + α) -bit image data DJ. The graph 223d shows the gradation of the (n + α) -bit image data DS and the image data DM, the graph 223e shows the gradation of the weighted average value EM, and the graph 223f shows the gradation of the (n + α) -bit image data DO. Is shown.

  An analog image signal SA as shown in the graph 223 a is input to the image display device 100 from the input terminal 1 to the receiving unit 2. The receiving unit 2 converts the analog image signal SA into digital image data DI (n bits) as shown in the graph 223b (binary gradation (X ′ and X ′ + 4)), and the original data bit expansion unit 5 is output.

  The original data bit expansion unit 5 converts the gradation X ′ of the image data DI of the graph 223b into gradation 4X ′, converts the gradation X ′ + 4 into gradation 4 (X ′ + 4), and shows the graph 223c. Such image data DJ is output to the gradation converter 28. Here, the gradation conversion unit 28 converts the gradation 4X ′ to the gradation 4Y and converts the gradation 4 (X ′ + 2) to the gradation 4 (Y + 2) by performing various gradation conversions. The image data DS as shown in the graph 223d is output to the one-dimensional fourth-order ε filter unit 61.

  FIG. 40 is a diagram illustrating data generated by the image display apparatus according to the second embodiment when an analog image signal that undergoes a conversion jump with a sudden change in gradation is input. In FIG. 40, when the pixel at the pixel position ic in the graph 223d is the target pixel P (c), the difference data ED (k) generated based on the image data DM (k) and the image data DM (k), The correspondence relationship between the determination data EE (k), f {ED (k)}, the weighted average value EM, and the threshold data TH (k) is shown.

  The data storage unit 7 calculates DM (l2) = 4Y, DM (l1) = 4Y, DM (c) = 4Y, DM (r1) = 4Y + 8, respectively, as the first difference calculation unit 8-1 to fourth difference calculation. Output to section 8-4.

  The first difference calculation unit 8-1 outputs ED (l2) = DM (l2) -DM (c) = 4Y-4Y = 0, and the second difference calculation unit 8-2 outputs ED (l1). = DM (l1) -DM (c) = 4Y-4Y = 0, and the third difference calculation unit 8-3 outputs ED (c) = DM (c) -DM (c) = 4Y-4Y = 0 is output, and the fourth difference calculation unit 8-4 outputs ED (r1) = DM (r1) -DM (c) = (4Y + 8) -4Y = 8. Accordingly, “0” is input to the first ε determination unit 9-1 to the third ε determination unit 9-3, and “8” is input to the fourth ε determination unit 9-4.

  The ε calculator 30 is set so that all the threshold data TH (l2) to TH (r1) are output as “4” when the image data DS is near 4Y. At this time, in the image display device 110 according to the present embodiment, the ε calculation unit 30 interpolates the threshold corresponding to the image data DS based on the threshold table for each gradation.

  When the image data DS = 4Y or 4Y + 8, the threshold data TH (l2) = 4, the threshold data TH (l1) = 4, the threshold data TH (c) = 4, and the threshold data TH (r1) = 4 are the first. The information is input to the ε determination unit 9-1 to the fourth ε determination unit 9-4. Accordingly, “0” is input to the first ε determination unit 9-1 to the third ε determination unit 9-3, and “8” is input to the fourth ε determination unit 9-4. Since the difference data ED (l2) to ED (c) is equal to or less than the respective threshold data TH (l2) to TH (c), the determination data EE (l2) to EE (c) is “1”, and the difference data ED ( Since r1) is larger than the threshold data TH (r1), the determination data EE (r1) is “0”.

When the determination data EE (k) is “1”, the determination additional weight average unit 10 multiplies and adds the difference data ED (k) to the coefficient _ak , and the determination data EE (k) is “0”. Is not added. When all the coefficients a _k (= a _l2, a _l1 , a _c , a _r1 ) are 0.25, in the example shown in FIG. 40, the output (weighted average value EM) of the determination additional weight average unit 10 is It is given by the following equation (10).
EM
= A _l2 × ED (l2) + a _l1 × ED (l1) + a _c × ED (c)
= (0.25 × 0) + (0.25 × 0) + (0.25 × 0)
= 0
... (10)

  In the image display device 100, the above processing is performed on the image data DS supplied from the original data bit expansion unit 5 with each pixel as a target pixel in order, and the same calculation as Expression (10) is performed.

  A graph 223e shows the gradation of the weighted average value EM (the weighted average value EM when the pixel at each pixel position i is the target pixel) corresponding to the image data DM of the graph 223d. The determination additional weight average unit 10 outputs the weighted average value EM to the data addition unit 11. The data adding unit 11 adds the image data DS shown in the graph 223d and the weighted average value EM shown in the graph 223e, and outputs the image data DO shown in the graph 223f.

  As shown in the graph 223f, the image data DO has a steep change like the input signal (analog image signal SA) or the image data DI. The ε filter can preserve the sharpness of a region that changes drastically and greatly even when the change in gradation is large.

  In the present embodiment, when an image data signal as shown by a graph 222c in FIG. 37 is input to the gradation converting unit 28, an image data signal SA as shown by a graph 222d in FIG. 37 is output. Also, when an image data signal such as a graph 223c of FIG. 39 is input to the gradation converting unit 28, an image data signal SA such as a graph 223d of FIG. 39 is output.

  The graph 222d in FIG. 37 and the graph 223d in FIG. 39 are gradation jumps having the same gradation difference. However, in the graph 222c in FIG. 37, the gradation change is gentle before gradation conversion, and in the graph 223c in FIG. Before gradation conversion, there is a steep gradation change. For this reason, it is desirable to interpolate gradation jumps for gradual gradation changes (in the case of FIG. 37). On the other hand, it is desirable to maintain a steep gradation change with respect to a steep gradation change (in the case of FIG. 39). In the present embodiment, the ε calculation unit 30 is set so as to output the threshold 8 for the input gradation near the gradation 4X, and outputs the threshold 4 for the input gradation near the gradation 4X ′. If set, it is possible to perform an expected operation (an operation that interpolates a gradation jump for a gradual gradation change and maintains a gradation change for a steep gradation change).

  As a result, in this embodiment, even if the gradation increased due to bit expansion changes due to gradation conversion such as gamma conversion, it can be treated as small amplitude noise, while maintaining a sharp change in the image such as the contour. The number of effective gradations can be increased.

  FIG. 41 is a flowchart showing a processing procedure of the image display apparatus according to the present embodiment described above. First, when the analog image signal SA is input to the input terminal 1, the receiving unit 2 receives the analog image signal SA and outputs n-bit image data DI (step ST11).

  The image data DI output from the receiving unit 2 is input to the original data bit extending unit 5 of the multi-gradation processing unit 3. The original data bit extension section 5 extends the image data DI by α bits and outputs (n + α) bits of image data DJ (step ST12).

  The image data DJ output from the original data bit expansion unit 5 is input to the gradation conversion unit 28. The gradation conversion unit 28 performs gradation conversion on the image data DJ and outputs (n + α) -bit image data DS (step ST13).

  The ε calculation unit 30 receives n + α-bit image data DS. The ε calculation unit 30 performs an interpolation operation (ε calculation) to calculate a threshold value, and outputs threshold value data TH (1) to TH (m) (ST14).

  The one-dimensional m-th order ε filter unit 60 receives (n + α) -bit image data DS and threshold data TH (1) to TH (m). The one-dimensional m-th order ε filter unit 60 increases the number of gradations in the slowly changing region and outputs the image data DO (step ST15). The image data DO is input to the display unit 4. The display unit 4 displays an image based on the image data DO (step ST16).

  FIG. 42 is a diagram illustrating another configuration example (1) of the image display device according to the second embodiment. 42, the same number is attached | subjected about the component which achieves the same function as the image display apparatus 110 shown in FIG. 33, and the overlapping description is abbreviate | omitted.

  In the image display device 112, the gradation conversion unit 28 is in the preceding stage of the original data bit expansion unit 5. When the analog image signal SA is input to the input terminal 1, the receiving unit 2 receives the analog image signal SA and inputs n-bit image data DI to the gradation converting unit 28.

  The gradation conversion unit 28 performs gradation conversion on the image data DI and inputs n-bit image data DJ to the original data bit expansion unit 5. The original data bit extension unit 5 extends the image data DJ by α bits and outputs (n + α) -bit image data DS. Then, the image data DJ output from the original data bit expansion unit 5 is input to the gradation conversion unit 28 and the one-dimensional m-order ε filter unit 60.

  In the image display device 112, if the threshold value is set in accordance with the characteristics of gradation conversion in the ε calculation unit 30, it is possible to increase the number of gradations in a region where the gradation changes gradually without reducing the sharpness of the image. It becomes.

  FIG. 43 is a diagram illustrating another configuration example (2) of the image display device according to the second embodiment. 43, the same number is attached | subjected about the component which achieves the same function as the image display apparatus 110 shown in FIG. 33, and the overlapping description is abbreviate | omitted.

  In the image display device 113, the gradation conversion unit 28 (not shown in FIG. 43) is in front of the reception unit 2. As a result, in the image display apparatus 103, data that has been subjected to gradation conversion in advance is input to the receiving unit 2. When the analog image signal SA subjected to gradation conversion is input to the input terminal 1, the receiving unit 2 receives the analog image signal SA and inputs n-bit image data DI to the original data bit extending unit 5. .

  The original data bit extension unit 5 extends the image data DI by α bits and outputs (n + α) -bit image data DS. The image data DJ output from the original data bit expansion unit 5 is input to the ε calculation unit 30 and the one-dimensional m-order ε filter unit 60.

  Similarly to the image display device 110 shown in FIG. 33 and the image display device 112 shown in FIG. 42, the image display device 113 can set the threshold value according to the characteristics of gradation conversion without reducing the sharpness of the image. It is possible to increase the number of gradations in a region where the tone gradually changes.

  FIG. 44 is a diagram illustrating another configuration example (3) of the image display device according to the second embodiment. 44, the same reference numerals are given to the constituent elements that achieve the same functions as those of the image display device 104 shown in FIG. 30 and the image display device 110 shown in FIG. To do.

  Compared to the image display device 112 shown in FIG. 25, the image display device 114 is not provided with the original data bit expansion unit 5 and is provided with a determination instead of the determination additional weight average unit 10 and the data addition unit 11. A weighted average unit 32 and a data addition unit 33 are provided.

  The determination additional weighted average unit 32 performs weighted average calculation and bit extension based on the determination data EE and the difference data ED, and outputs a weighted average value EM that is bit-extended by α bits. In the image display device 114, for example, the bit addition is performed by generating the data as the average data EM also with the numerical values of the decimal places appearing when the arithmetic operation of the determination additional weighted average is performed as in the example of FIG. Can be done. In the data adding unit 33, the input image data DM (c) is bit-extended to (n + α) bits and added.

  Thus, in the image display device 114, bit expansion is not performed before the ε filter, but is performed during the calculation of the ε filter. With the configuration described above, the same effects as those of the image display device 112 shown in FIG. 42 can be obtained.

  In the image display device 110 shown in FIG. 33, the case where the ε filter is a one-dimensional ε filter has been described. However, the present embodiment is not limited to the one-dimensional ε filter. 45 and 46 are diagrams showing a configuration of an image display device including a two-dimensional ε filter that the ε filter processes in the horizontal direction and the vertical direction. 45 and 46, the same numbers are assigned to components that achieve the same functions as those of the image display devices 105 and 106 shown in FIGS. 31 and 32 and the image display device 110 shown in FIG. Therefore, a duplicate description is omitted.

  The image display device 115 shown in FIG. 45 includes a two-dimensional mth-order ε filter unit 62 as an ε filter. Similar to the one-dimensional m-order ε filter unit 6, the two-dimensional m-order ε filter unit 62 is connected to the gradation conversion unit 28, the ε calculation unit 30, and the display unit 4.

  The two-dimensional m-th order ε filter unit 62 performs processing (ε filtering processing) on a two-dimensional region of horizontal pixels (h) × vertical pixels (v). That is, the two-dimensional m-th order ε filter unit 62 stores a sharp change based on data of pixels arranged in a two-dimensional direction (vertical direction, horizontal direction) with the pixel of interest at the center, and a small amplitude component. Is used as an edge-preserving smoothing filter that performs smoothing by treating the noise as noise.

  45 includes a data storage unit 34, a first difference calculation unit 8-1 to an m-th difference calculation unit 8-m, and a first ε determination unit 9-1 to the first. Image data that includes an ε determination unit 9-m for m, a determination additional weighted average unit 10, and a data addition unit 11, and in which the effective number of gradations is increased with respect to a vertical gradation change of the image data DS The VDO is output to the one-dimensional h-order horizontal ε filter unit 63b.

  The image display device 116 shown in FIG. 46 includes a one-dimensional v-th order vertical ε filter unit 63a and a one-dimensional h-th order horizontal ε filter unit 63b as ε filters. The one-dimensional vth-order vertical ε filter unit 63a is connected to the gradation conversion unit 28, the first ε-calculation unit 30-1, and the one-dimensional h-order horizontal ε filter unit 63b. In addition, the one-dimensional h-order horizontal ε filter unit 63 b is connected to the gradation conversion unit 28, the second ε calculation unit 30-2, and the display unit 4.

  In the image display device 116, as compared with the image display device 105, a first ε calculation unit 30-1 is provided instead of the first ε selection unit 29-1, and a second ε selection unit 29-2. A difference is that a second ε calculation unit 30-2 is provided instead of the above.

  The one-dimensional v-th order vertical ε filter unit 63 a includes a V data storage unit (vertical direction data storage unit) 15, a first V difference calculation unit (vertical direction difference calculation unit) 16-1 to a vth V difference calculation unit 16. -V, first Vε determination unit (vertical direction ε determination unit) 17-1 to vth Vε determination unit 17-v, V determination additional weight average unit (vertical direction determination additional weight average unit) 18, and V data An adder (vertical adder) 19 is provided.

  The one-dimensional h-order horizontal ε filter unit 63b includes an original data storage unit 20, a first original data difference calculation unit 21-1 to an hth original data difference calculation unit 21-h, a first Hε determination unit ( (Horizontal direction ε determination unit) 22-1 to h-th Hε determination unit 22-h, H data storage unit (horizontal direction data storage unit) 23, first H difference calculation unit (horizontal direction difference calculation unit) 24-1 To an h-th H difference calculation unit 24-h, an H determination additional weight average unit (horizontal direction determination additional weight average unit) 25, and an H data addition unit (horizontal direction data addition unit) 26.

  The one-dimensional v-th order vertical ε filter unit 63a performs processing in the vertical direction of the image on the (n + α) -bit original data. The one-dimensional v-th order vertical ε filter unit 63a is based on the pixel data aligned in the vertical direction with respect to the target pixel, and stores an abrupt change while smoothing by treating a small amplitude component as noise. It is used as a mold smoothing filter. The one-dimensional vth-order vertical ε filter unit 63a has a role of increasing the effective number of gradations of the image data VDO based on a change in gradation in the horizontal direction of the image data DS.

  The one-dimensional h-order horizontal ε filter unit 63b performs processing in the horizontal direction of the image on the (n + α) -bit data output from the one-dimensional v-th order vertical ε filter unit 63a. The one-dimensional h-th order horizontal ε filter unit 63b is based on the pixel data aligned in the horizontal direction with respect to the target pixel, and stores an abrupt change while smoothing by treating a small amplitude component as noise. It is used as a mold smoothing filter. The one-dimensional h-order horizontal ε filter unit 63b has a role of increasing the effective number of gradations of the image data VDO based on a change in gradation in the horizontal direction of the image data DS.

  The ε fill that performs the two-dimensional processing as described above, and the threshold control units (the first ε calculation unit 30-1 and the second ε calculation unit 30-2) that change the threshold value ε according to the input gradation. Therefore, the size of the edge to be held for each gradation can be set both in the vertical direction and in the horizontal direction.

  In the first and second embodiments, the case where α = 2 and n-bit image data is expanded to n + 2 bits has been described in detail. However, the present invention is not limited to α = 2. Similarly, although the order m of the ε filter has been set to 4, the present invention is not limited to m = 4.

  In the first and second embodiments, the difference data ED (c), ED (c, c), and VED (c) between the image data of the target pixel are always “0”. Ε determination results (determination data EE (c), EE (c, c), VEE (c), BED (c)) are always “1”. For this reason, the difference calculation unit for obtaining the difference between the image data of the target pixel and the output (difference data ED (c), ED (c, c), VED (c), BED (c)) are larger than the threshold ε. The ε determination unit (such as the third ε determination unit 9-3 shown in FIG. 5) is omitted, and the determination additional weight average unit 10, the V determination additional weight average unit 18, and the H determination are added. The weighted average unit 25 may add (or ignore) “0” as the difference data ED (c), ED (c, c), VED (c), and HED (c).

  Also, the difference calculation unit 24-3 illustrated in FIG. 32 obtains a difference between the same data HDM (c), and the difference is always 0, so the third H difference calculation unit 24-3 is omitted. Then, the H determination additional weight average unit 25 may add (or ignore) zero as HDM (c).

  In the present embodiment, the ε calculating unit 30, the one-dimensional m-order ε filter unit 60, the one-dimensional fourth-order ε filter unit 61, the two-dimensional m-order ε filter unit 62, the one-dimensional v-order vertical ε filter unit 63a, Although the one-dimensional h-order horizontal ε filter unit 63b is configured separately, the one-dimensional m-order ε filter unit 60, the one-dimensional fourth-order ε filter unit 61, the two-dimensional m-order ε filter unit 62, the one-dimensional v-th order vertical The ε filter unit 63 a and the one-dimensional h-order horizontal ε filter unit 63 b may include the ε calculation unit 30.

  Thus, according to the second embodiment, as in the first embodiment, the gradation increased by the bit expansion is smoothed using the ε filter. The number of gradations of the image data can be increased without impairing the sharpness of the image. Therefore, it is possible to eliminate the pseudo contour caused by the missing image level and reduce the image quality deterioration due to the pseudo contour.

  Further, since the threshold value of the gradation is interpolated from the threshold value table and the threshold value data TH corresponding to the image data is output, even if the threshold values corresponding to all the gradation values are not set in the table, It is possible to easily determine whether or not the difference data ED is larger than the threshold data TH.

Embodiment 3 FIG.
So far, the smoothing filter has been described as the ε filter, but the smoothing filter is not limited to the ε filter, and the smoothing filter preserves the sharpness of the portion where there is a steep and large change, Any edge-preserving smoothing filter that smoothes only small changes may be used. For example, a trimmed average value filter (DW-MTM filter) or a bilateral filter may be used in addition to the ε filter.

  The trimmed average value filter (DW-MTM filter) is, for example, Non-Patent Document 2 (supervised by Takao Hinamoto, Mitsuji Muneyasu, Ryo Otaguchi, “Nonlinear Digital Signal Processing” Asakura Shoten, March 20, 1999. p.72-74).

One-dimensional processing by the trimmed average value filter is expressed by equations (5) and (6). x (i) is the gradation of the input image data, and y (i) is the gradation of the output image data. Further, a _k is a coefficient, k is a relative pixel position from the target pixel, and ε is a threshold value.

Here, x _med is a median value of in-window data smaller than the filter window width m centering on the processing point. b _k is 1 if x ( _ik ) -x _med is less than or equal to the threshold ε, and 0 if it is less than or equal to the threshold ε.

b _k is 1 if x (i−k) −x (i) is less than or equal to the threshold ε, and 0 if the threshold is less than or equal to ε. That is, the trimmed average value filter of Expression (6) obtains a weighted average value excluding peripheral pixels having a large gradation difference from the target pixel.

  The ε filter obtains a weighted average value by replacing peripheral pixels having a large gradation difference with the target pixel by the gradation value of the target pixel. In this way, the trimmed average value filter is a filter that smooths only small changes while preserving the sharpness of a portion where there is a steep and large change, similar to the ε filter. Therefore, the same effect can be obtained even if a trimmed average value filter is used instead of the ε filter.

  Similarly, the same effect can be obtained by using another edge-preserving smoothing filter instead of the ε filter.

  In the present embodiment, the image display device 100 stores the data bit expansion unit that expands the number of bits of image data and expands the gradation of the image data, and stores the image data in the image data according to the gradation of the image data. A smoothing filter unit (an edge preserving smoothing filter including a threshold control unit) that determines the size of the edge to be placed and smoothes a predetermined gradation of the image data based on the determined edge size; Therefore, the size of the edge that can be stored in the filter can be changed according to the input gradation. Further, when the image data is subjected to gradation conversion, the threshold value can be changed in accordance with the gradation conversion. Therefore, low-amplitude components that cause noise can be removed while maintaining sharp edges, and the generation of pseudo contours in a digital image can be suppressed.

  In the above embodiment, focusing on the data in which the number of bits of the image data is expanded and the gradation of the image data is expanded, an edge preserving smoothing filter corresponding to the gradation of the image data is applied. Although described above, this is not particularly limited. For example, even if the data does not have an extended gradation, for example, the data of the image data can be compared with the data that has not been extended in the gradation, such as the gradation converted data. You may make it apply the edge preservation | save type | mold smoothing filter according to a gradation.

  As described above, the image processing apparatus, the image display apparatus, and the image processing method according to the present invention are suitable for multi-gradation of a digital image.

It is a figure which shows the structure of the image display apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the function f (u) of Formula (1). It is a figure for demonstrating the epsilon filter process by an epsilon filter. It is a figure which shows the relationship between a gradation and a threshold value. It is a figure which shows the structure of the image display apparatus of Embodiment 1 in the case of m = 4. It is a figure for demonstrating the A / D conversion process by a receiving part. It is a figure for demonstrating the bit expansion process by an original data bit expansion part. It is a figure for demonstrating the gradation conversion process in case a gradation changes gently. It is a figure which shows an example of a detailed structure of a data storage part. It is a figure for demonstrating the gradation of the image data output from a data storage part. It is a figure which shows the data produced | generated with the image display apparatus which concerns on Embodiment 1 when a gradation changes gently. It is a figure for demonstrating the concept of a weighted average. It is a figure which shows the weighted average value of the image data output from the data storage part shown in FIG. It is a figure for demonstrating the data addition process by a data addition part. FIG. 6 is a diagram for explaining an operation when an analog image signal whose gradation changes sharply and greatly is input to the image display device according to the first embodiment. It is a figure which shows the data produced | generated with the image display apparatus which concerns on Embodiment 1 when a gradation changes rapidly. FIG. 6 is a diagram for explaining an operation when an analog image signal that undergoes a conversion jump at a gradual gradation is input to the image display device according to the first embodiment. It is a figure which shows the data produced | generated with the image display apparatus which concerns on Embodiment 1 when the analog image signal which carries out the conversion jump with a gradual gradation is input. FIG. 6 is a diagram for explaining an operation when an analog image signal that undergoes a conversion jump with a sudden change in gradation is input to the image display device according to the first embodiment. It is a figure which shows the data produced | generated with the image display apparatus which concerns on Embodiment 1 when the analog image signal which carries out a conversion jump with a sudden change gradation is input. 3 is a flowchart illustrating a processing procedure of the image display apparatus according to the first embodiment. It is a figure for demonstrating the gamma conversion process by a gradation conversion part. It is a figure for demonstrating the gamma conversion process in case a gradation changes gently. It is a figure for demonstrating the gamma conversion process in case a gradation changes rapidly. It is a figure which shows another structural example (1) of the image display apparatus which concerns on Embodiment 1. FIG. It is a figure for demonstrating the gamma conversion process by the gradation conversion part shown in FIG. It is a figure for demonstrating the gamma conversion process by the gradation conversion part shown in FIG. 25 in case a gradation changes gently. It is a figure for demonstrating the gamma conversion process by the gradation conversion part shown in FIG. 25 in case a gradation changes rapidly. It is a figure which shows another structural example (2) of the image display apparatus which concerns on Embodiment 1. FIG. It is a figure which shows another structural example (3) of the image display apparatus which concerns on Embodiment 1. FIG. It is a figure which shows another structural example (4) of the image display apparatus which concerns on Embodiment 1. FIG. It is a figure which shows another structural example (5) of the image display apparatus which concerns on Embodiment 1. FIG. It is a figure which shows the structure of the image display apparatus which concerns on Embodiment 2 of this invention. FIG. 6A is a diagram (1) illustrating a relationship between a gradation and a threshold value used in an image display device according to a second embodiment. FIG. 10B is a diagram (2) illustrating a relationship between a gradation and a threshold value used in the image display device according to the second embodiment. It is a figure which shows the structure of the image display apparatus of Embodiment 2 in the case of m = 4. FIG. 10 is a diagram for explaining an operation when an analog image signal that undergoes a conversion jump at a gradual gradation is input to the image display device according to the second embodiment. It is a figure which shows the data produced | generated with the image display apparatus which concerns on Embodiment 2 when the analog image signal which carries out the conversion jump with a gradual gradation is input. FIG. 10 is a diagram for explaining an operation when an analog image signal that undergoes a conversion jump with a sudden change in gradation is input to the image display device according to the second embodiment. It is a figure which shows the data produced | generated with the image display apparatus which concerns on Embodiment 2 when the analog image signal which carries out the conversion jump with a sudden change gradation is input. 10 is a flowchart illustrating a processing procedure of the image display apparatus according to the second embodiment. It is a figure which shows another structural example (1) of the image display apparatus which concerns on Embodiment 2. FIG. It is a figure which shows another structural example (2) of the image display apparatus which concerns on Embodiment 2. FIG. It is a figure which shows another structural example (3) of the image display apparatus which concerns on Embodiment 2. FIG. It is a figure which shows another structural example (4) of the image display apparatus which concerns on Embodiment 2. FIG. It is a figure which shows another structural example (5) of the image display apparatus which concerns on Embodiment 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Input terminal 2 Receiving part 3 Multi-gradation processing part 4 Display part 5 Original data bit expansion part 7, 34 Data storage part 8 Difference calculation part 9 ε determination part 10, 32 Judgment addition multiple average part 11, 33 Data addition part 15 V data storage unit 16 V difference calculation unit 17 Vε determination unit 18 V determination additional weighted average unit 19 V data addition unit 20 original data storage unit 21 original data difference calculation unit 22 Hε determination unit 23 H data storage unit 24 H difference calculation Unit 25 H determination additional weighted average unit 26 H data addition unit 27 one-dimensional m-order ε filter unit with bit extension 28 gradation conversion unit 29 ε selection unit 30 ε calculation unit 60 one-dimensional m-order ε filter unit 61 one-dimensional fourth-order ε filter unit 62 2D m-order ε filter unit 63a One-dimensional v-order vertical ε filter unit 63b One-dimensional h-order horizontal ε filter unit 100-106, 110-116 Image display device

Claims (11)

In an image processing apparatus that interpolates the gradation of the image data by increasing the gradation of the image data,
A data bit expansion unit that expands the number of bits of the image data and expands the gradation of the image data; a threshold control unit that obtains a threshold value according to the gradation of the image data; An image processing apparatus comprising: a smoothing filter unit that smoothes a predetermined gradation of the image data while storing a predetermined edge; and an output unit that outputs image data processed by the smoothing filter unit. The image processing apparatus according to claim 1, wherein the data bit extension unit is arranged in a preceding stage of the smoothing filter. The smoothing filter unit includes the data bit extension unit;
The image processing apparatus according to claim 1, wherein the data bit extension unit extends the number of bits of image data that has been smoothed at a predetermined gradation by the smoothing filter unit. In an image processing apparatus that interpolates the gradation of image data,
An input unit that inputs the image data; a threshold control unit that obtains a threshold value according to a gradation of the image data; and a predetermined level of the image data while storing a predetermined edge in the image data according to the threshold value An image processing apparatus comprising: a smoothing filter unit that smoothes a tone; and an output unit that outputs image data processed by the smoothing filter unit. A gradation converting unit for converting the gradation of the image data;
The image processing apparatus according to claim 1, wherein the smoothing filter performs a smoothing process on a predetermined gradation of the image data subjected to gradation conversion. The image processing apparatus according to claim 5, wherein the threshold value control unit obtains a threshold value according to characteristics of the gradation conversion unit. The threshold value control unit obtains a threshold value corresponding to the gradation of the image data from information in which the gradation and the threshold value are associated with each other, and outputs the threshold value to the smoothing filter. 5. The image processing apparatus according to 4. The threshold value control unit calculates a threshold value according to the gradation from the gradation of the image data, and outputs the calculated threshold value to the smoothing filter. The image processing apparatus described. The image processing apparatus according to claim 1, wherein the smoothing filter unit is an ε filter. In an image display device that interpolates the gradation of image data and displays an image using an image obtained by interpolating the gradation,
A receiving unit that receives an image signal and generates image data, an image processing device according to claim 1, and a display unit that displays data processed by the image processing device. Image display device. In the image processing method for interpolating the gradation of the image data by multi-grading the image data,
Expanding the number of bits of the image data to expand the gradation of the image data; obtaining a threshold value according to the gradation of the image data; and storing a predetermined edge in the image data according to the threshold value An image processing method comprising: smoothing a predetermined gradation of the image data while outputting the smoothed image data.

Images