JPH0638024A - Image processor - Google Patents

Abstract

PURPOSE:To provide an enlarged image while preserving the gradation change of the image before the enlargement, namely, sharpness at the edge part of the image. CONSTITUTION:At the image processor to enlarge the image by interpolating picture elements, the change of gradation between adjacent picture elements is detected based on RGB digital data (discrete pixel information) and especially, a conversion rate decision part 513 and a change rate setting part 506 adjust the change rate of gradation at the interpolated picture elements corresponding to the degree of the detected gradation change and generate the pixel information corresponding to the interpolated picture elements in correspondence to the adjusted change rate corresponding to an enlargement rate 505.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, for example, an image processing apparatus for processing a video image.

[0002]

2. Description of the Related Art Conventionally, in a device of this type, one screen of an image signal which changes with time, that is, a video signal is selected and stored (recorded) on paper as an image or converted into RGB digital data. And stored it on a recording medium. In the case of such an image processing apparatus, as shown in FIG. 12, the gradation of each pixel changed. FIG. 12 (a) is before expansion and FIG.
(B) shows each after expansion. Pixels Pa, Pb, P
c, Pd, and Pe are adjacent pixels before and after the pixels P0 and P2, and the pixels P'c1, P'c2, P'01, P'02,
P'21 and P'22 are adjacent interpolation pixels before and after the pixels P0 and P2, and inserted between them.

[0003]

In the above prior art, as shown in FIG. 12A, when the gradation of the pixel P0 to the pixel P2 greatly changes, the gradation of the enlarged image changes. It changes monotonously as shown in FIG. In other words, it changes as a linear function. That is, the sharpness of the edge portion of the image disappeared, and the entire enlarged image became a blurred image.

The present invention has been made in view of the above-mentioned drawbacks of the conventional example, and an object of the present invention is to preserve the change in the gradation of the image before enlargement, that is, the sharpness of the edge portion of the image. However, the point is to provide an image processing apparatus capable of obtaining an enlarged image.

[0005]

[Means for Solving the Problems]
In order to achieve the object, an image processing device according to the present invention is an image processing device that enlarges an image by pixel interpolation,
Detecting means for detecting a gradation change between adjacent pixels based on the inputted discrete pixel information, and adjusting a gradation change rate of the interpolated pixel according to the degree of the detected gradation change. And adjusting means and generating means for generating pixel information corresponding to interpolation pixels according to the change rate adjusted by the adjusting means.

[0006]

According to this structure, the detecting means detects the gradation change between the adjacent pixels on the basis of the input discrete pixel information, and the adjusting means responds to the detected gradation change degree. Then, the rate of change of the gradation of the interpolated pixel is adjusted, and the generation means generates pixel information corresponding to the interpolated pixel according to the rate of change adjusted by the adjustment means.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings. FIG. 8 is a block diagram showing the configuration of a general image processing apparatus. In the figure,
The signal source 100 outputs a composite image signal as a video signal. NTSC, PA as composite signal
The L, SECAM system is a typical example, but the following description will be made assuming that the signal source 100 outputs an NTSC composite signal for simplicity.

The image processing apparatus 200 according to the general example has the following configuration. That is, 201 is an input section having a terminal through which the image processing apparatus 2 can input the image signal, and a buffer circuit, a terminating resistor, etc., 202 is the input image signal, that is, the NTSC composite signal, in luminance (Y). Y / C separation unit for separating a signal and a color (C) signal, 203 is Y / C
A decoder that generates red, green, and blue RGB signals from the luminance signal and the color signal separated by the C separation unit 202, and the RGB signal separated by the decoder 203 is the A / D in the subsequent stage.
It includes conversion errors of the conversion units 2051, 2052, and 2053. Reference numerals 2041, 2042, and 2043 are adjustment volumes provided to remove the error.

FIG. 9 shows N input to the image processing apparatus 200.
It is a figure showing the error of the TSC composite signal and the converted RGB signal. FIG. 9A shows the image processing device 20.
NTSC composite signal input to 0, sync chip level is -40IRE, white level is 100I
It is a white raster signal of 100% of RE. Figure 9
(B), (c), (d) are converted RGB signals, and the maximum value of the waveform includes an error. The A / D converters 2051, 2052, 2053 convert the analog RGB signals into digital signals, that is, discrete pixel information (hereinafter referred to as “discrete information”), sample and hold circuits, and aliasing at the time of quantization. A low pass filter is provided to limit the band of the original signal to prevent it. 206
1, 2062, 2063 are memories for storing quantized RGB discrete values, and memories 2061, 206
2,2063 is a FIFO even if it is a dynamic memory
Etc. may be used.

An interpolating unit 207 interpolates the image data of the NTSC composite signal, which has a smaller amount of information than the resolution of the copying machine 400. Here, it is assumed that the copying machine 400 is a copying machine using an inkjet head,
With such a high resolution, the information amount of the NTSC image signal is very small for the copying machine 400. When the NTSC image signal sampled at a frequency about twice that of the color subcarrier is printed at 400 dpi, the image size is only a few centimeters square.

In order to effectively use the space of the paper provided to the copying machine 400, an enlarged image is printed. At this time, the interval between adjacent pixels is widened. With this image as it is, the image will be full of gaps. Therefore,
The interpolation unit 207 obtains the data of the pixels to be embedded between the original images by calculation from the data of the original image, embeds the data as interpolation pixels, and as a result, the enlarged image with no gap is recorded by the copying machine 400.

Reference numeral 208 denotes an output unit for outputting the RGB digital data, that is, the digital data so as to conform to an interface prepared for obtaining the discrete information, that is, a serial number such as RS-232C. An interface or a parallel interface such as Centronics that transmits binary / multivalued is considered.

Reference numerals 2091, 2092 and 2093 denote the memory 2
D / A converters for converting the RGB digital data stored in 061, 2062, 2063 into analog values, and the D / A converters 2091, 2092, 209
3 includes a low-pass filter that removes spurious components of the sampling frequency. D / A converter 2091,
The analog RGB signals converted into analog signals by 2092 and 2093 are the D / A conversion units 2091,
Conversion errors of 2092 and 2093, and encoder 211
The error of is included. Reference numerals 2101, 1022, and 2103 are adjustment volumes provided to remove the error.
Reference numeral 211 denotes an encoder that combines an analog RGB signal with the sync signal sent from the decoder 203 to generate an NTSC composite signal, and 212 is provided for confirming an image input to the image processing apparatus 200. The switch is a switch that switches the image signal bypassed from the unit 201 and the RGB digital data, that is, the image stored in the memories 2061, 2062, and 2063, and sends the image to the monitor 3.

When confirming the image on the monitor 300, the image signal input to the image processing apparatus 200 and the RGB digital data stored in the image processing apparatus 200, that is, the screen for monitoring that the image is not synchronized are displayed. It will be out of sync and will cause a distorted screen. In addition, the sync signal reproduced from the digital data stored in the memories 2061, 2062, and 2063 cannot obtain the quality that can be used as the sync signal. In order to prevent this, the decoder 203 is provided with means for extracting the sync signal, and the sync signal is sent to the encoder 211 to prevent synchronization deviation. The extracted sync signal is generally processed by PLL or the like so that the phases of the bursts in the even field and the odd field can be sufficiently preserved.

Reference numeral 213 is an NTSC composite signal output section. It has a general-purpose terminal and a buffer circuit.
The control unit 214 controls the A / D conversion units 2051, 2052, 20.
53, the memories 2061, 2062, 2063, the D / A conversion units 2091, 2092, 2093, the interpolation unit 207, and the output unit 208 generate necessary timing control signals and the like.
In addition, communication control necessary for information transmission with an external device is performed, and a command from the operation unit 215 is fetched. The control unit 214 may be configured by a circuit including a CPU or only a logic circuit.

With the above configuration, the control unit 214 generates a necessary control signal to each unit in response to an image fetching command from the operation unit 215, and an image at a certain moment is stored in the memories 2061 and 20.
62, 2063. Memory 206 as required
The RGB digital data stored in 1,2062,2063, that is, the image is confirmed by the monitor 300, the image is sent to the copying machine 400 as RGB digital data, and the image is formed on a sheet by the data.

The details of the interpolation unit 207 will be described. In FIG. 10, (b) and (e) are output images of the copying machine 4 when the image is not enlarged. (A) of FIG.
Shows a state in which a part of FIG. 10B is enlarged and displayed. P0, P1, P2, and P3 are pixels when the NTSC composite signal output from the signal source 1, that is, the video signal is converted into discrete information. P0, P
1, P2 and P3 are adjacent pixels. The image horizontal direction is X and the image vertical direction is Y. xi and yi represent the distance from P0. Moreover, P0, P1, P2, and P3 represent the gradation of a pixel.

The image may be uniformly magnified in the XY direction or may be magnified independently in the X and Y directions. Figure 1
0 (c) is a diagram when the image of FIG. 10 (b) is doubled in the Y direction. FIG. 10F is a diagram when the image of FIG. 10E is magnified twice in the X-Y directions. For simplification, description will be given when the image is doubled in the Y direction.
P ′ and P ″ are pixels that interpolate between pixels. The gradation of the interpolated pixel is obtained by the following equations (1) and (2): P ′ = (P2−P0) × (Y2 / y1) + P0 (1) P ″ = (P3−P1) × (y2 / y1) + P1 (2) The pixel P ′ and the pixel P ″ thus obtained are inserted at a position of y2 = y1 / 2. By inserting this between adjacent pixels, a double image can be obtained in the Y direction. it can.

Pixels P, P '"and P""are interpolated pixels obtained when the image is doubled in the XY directions.
The gradations of the pixels P, P ′ ″ and P ″ ″ are obtained by the following equations (3) and (4) as in the case of doubling in the Y direction. That is, P ″ ′ = (P1−P0) × (x2 / x1) + P0 (3) P ″ ″ = (P3−P2) × (x2 / x1) + P2 (4) P = (P ′ “″ −P ″”) × (y2 / y1) + P ′ ″ (5).

Interpolation unit 207 for realizing the above processing
A detailed block diagram of the above is shown in FIG. For simplification, the case of the enlargement process of the R pixel in the Y direction will be described. The processing of GB pixels is performed in the same manner. Also, when enlarging in the XY direction, processing may be performed based on the same concept. Reference numeral 501 is a pixel position counter for confirming the position of the pixel stored in the memory 2061 on the image. That is, the positions of the pixels P0 and P2 are shown. Reference numerals 5021 and 5022 are latches for temporarily storing the data of the pixel P2 adjacent to the pixel P0 when focusing on the pixel P0. 503 is a subtractor that calculates the difference in gradation of the pixel. The gradation difference P2-P0 of the pixel is calculated. Reference numeral 504 is a divider for obtaining the gradation of the interpolation pixel by the enlargement ratio: N and the position of the interpolation pixel: i. For example, when the magnification is doubled, P '= (P2-P0) / 2 + P0 (6) as in the following expression (6). Further, when enlarged three times, pixels P0 and P2
There are two interpolation pixels inserted between, and when the first interpolation pixel is P'01 and the second interpolation pixel is P'02, the respective gradations are as shown in the following equations (7) and (8). P'01 = (P2-P0) / 3 + P0 ... (7) P'02 = (P2-P0) * (2/3) + P0 ... (8) The general formula is N: enlargement ratio (N = 2, 3, 4,
,): I: interpolation pixel position (i = 1, 2, 3, ...), and as in the following expression (9), P′0i = (P2−P0) × (i / N) + P0 (9) ). 505 gives a coefficient N to the divider 504 according to the enlargement ratio designated by the control unit 214. Reference numeral 506 gives a gradation change rate coefficient at the interpolation pixel position designated by the control unit 214. The rate of change here is i = 1, 2, 3, ... Reference numeral 507 denotes an adder for adding the gradation of the pixel of interest, here the pixel P0, to the result obtained from the divider 504, 511
Is a latch for temporarily storing the data of each interpolation pixel, and the image data is sent to the copying machine 400 in the order of RGB as 8-bit parallel data. A copying machine 40 displays the series of pixel data before enlargement and the processed interpolated pixel data 512.
0 is an array part that rearranges in the order of loading. <First Embodiment> First, an image processing system according to a first embodiment of the present invention will be described.

FIG. 7 is a block diagram showing the image processing system according to this embodiment. In the figure, 1 is a signal source for generating a time-varying image signal, 2 is an image processing apparatus in the present embodiment, and the image processing apparatus 2 selects a screen of the image signal and stores it in a storage means. Temporarily store by. Reference numeral 3 denotes an image monitor prepared for confirming the image temporarily stored by the image processing apparatus 2, and 4 stores the image signal converted into discrete information by the image processing apparatus 2 as discrete information. The storage device is a storage device, a device that saves an image on another medium such as paper such as a copying machine, or a copying machine that analyzes the discrete information. The copying machine 4 is a color copying machine using a laser beam or a bubble jet.

FIG. 1 is a block diagram showing the arrangement of an image processing apparatus according to this embodiment. In the following description, the configuration of FIG. 1 will be described only for the parts different from FIG. 11. In FIG. 1, reference numeral 513 denotes a difference in gradation between adjacent pixels obtained from the subtractor 503, that is, a change that determines the gradation change rate of the interpolation pixel inserted between the pixel P2 and the pixel P0 from P2-P0. This is a rate determining unit, and the change rate determining unit 513 changes the gradation change rate coefficient given from the change rate setting unit 506 to the divider 504.

In explaining the present embodiment, it is assumed that a three-fold enlarged image is obtained in the Y direction. An example showing changes in gradation of adjacent interpolation pixels is shown. P'is the first interpolation pixel
01 and the second interpolation pixel is P'02, the respective gradations are as shown in the following equations (10) and (11): P'01 = (P2-P0) * (0.2 / 3 ) + P0 ... (10) P'02 = (P2-P0) * (1.5 / 3) + P0 ... (11). The change in gradation at this time is shown in FIG.

FIG. 2 shows a state of gradation change of an enlarged image according to this embodiment. The above expressions (10) and (11) are expressions obtained when the difference P2-P0 between the gradation data of the adjacent pixels exceeds a certain value, that is, the threshold value. This is an example, and the change rate determination unit 513 includes some threshold values and a means for varying the change rate according to the threshold values. The general formula is N: enlargement ratio (N = 2, 3, 4, ...), i: interpolation pixel position (i = 1, 2, 3, ...), and pixel P0 to pixel P2 depending on the gradation difference between adjacent pixels. The function that determines the rate of change of the gradation of the adjacent interpolation pixel that is inserted between f (P2-P0) i
Then, as in the following expression (12), P'0i = {f (P2-P0) i * (P2-P0)} / N + P0 (12)

The function f (P2-P0) i is a continuous function or a discontinuous function in the range in which the gradation of the adjacent interpolation pixel inserted between the pixel P0 and the pixel P2 is obtained. I don't mind. The function f (P2-P0) i is the pixel P0.
When the solution of the second derivative f ″ (P2−P0) i of the function is positive in the range of obtaining the gradation of the adjacent interpolation pixel inserted between the pixel P2 and the pixel P2, The change in the tone becomes sharp and the edge of the image is preserved.

As an effect of the above, when the image of the video signal is enlarged and the image is recorded by the copying machine, the gradation change rate of the adjacent pixels, that is, the sharpness of the edge is preserved to form an enlarged image without blur. It becomes possible to do. As described above, according to the first embodiment, it is possible to obtain an enlarged image while preserving the gradation change of the image before enlargement, that is, the sharpness of the edge portion of the image. <Second Embodiment> Next, a second embodiment will be described.

FIG. 3 is a block diagram showing the arrangement of an image processing apparatus according to the second embodiment. The configuration of FIG. 3 will be described only for the parts different from those of FIG. In FIG. 3, 502
When the pixel P0 is focused on, the pixel P3
This is a latch for temporarily storing the 4th gradation data. When the pixel adjacent to the pixel P0 is P2, the pixel P4 is the pixel P.
2 adjacent pixels. Reference numeral 515 is a subtracter for obtaining the gradation difference between the pixel P4 and pixel P0, and 516 is the adjacent pixel P4 and P4.
2, a comparator for determining the direction of the gradient of the gradation change of the adjacent pixels P2 and P0.

FIG. 4 is a diagram showing changes in gradation of adjacent interpolation pixels according to the second embodiment. Now, the function f (P2-P
It is assumed that 0) i, f (P4-P2) i is a continuous function in the range where the gradation of the adjacent interpolation pixel is obtained. Then, as shown in FIG. 4A, it is assumed that the difference in gradation from P0 to P2 is positive and the difference in gradation from P2 to P4 is negative. It is assumed that the gradation of the pixel P2 is significantly larger than the gradations of the pixels P0 and P4 and exceeds the threshold value of the change rate determining unit 513 that is determined in advance. Then, when it is desired that the gradation of the pixel P2 be emphasized, the change rate determination unit 513 uses the ratio obtained by the comparator 516 to change the gradation of the adjacent interpolation pixel within the range from the pixel P0 to the pixel P2. Second derivative f ”
The coefficient is given to the change rate setting unit 506 so that the solution of (P2-P0) i is positive. In addition, the change rate determination unit 513 determines that the second derivative f ″ (P
4-P2) The coefficient is given to the change rate setting unit 506 so that the solution of i becomes positive. This result is shown in FIG. 4 (b). Gradient gradient from pixel P0 to pixel P2, pixel P
The function of the comparator 516 may be set such that the solution of the second derivative f ″ (P4−P2) i becomes negative depending on the magnitude of the gradient of the gradation from 2 to the pixel P4. ,
The function f (P2-P0) i and the function f (P4-P2) i may be discontinuous functions in the range where the gradation of the adjacent interpolation pixel is obtained. The range in which the gradient of the gradation of the adjacent pixel is obtained is not limited to three pixels as in the second embodiment, but may be 4, 5,
The gradient of the gradation may be obtained between the pixels of 6, ... Or the area.

As an effect of the above, according to the present embodiment, not only the difference in gradation in a small range such as between adjacent pixels is preserved, but also the necessary sharpness of edges is maintained without destroying the atmosphere of the entire image. It becomes possible to save and obtain an enlarged image. <Third Embodiment> FIG. 5 is a block diagram showing the arrangement of an image processing apparatus according to the third embodiment.

The configuration of FIG. 5 will be described only for the parts different from those of FIG. In FIG. 5, when the pixel P0 is focused on, 5023 is a latch for temporarily storing the grayscale data of the immediately preceding pixel P4. When the pixel adjacent to the pixel P0 is P2, the pixel P4 is a pixel adjacent to the pixel P2. Reference numeral 517 denotes an edge processing unit for performing image edge enhancement processing on pixels P0, P2 and P4 before enlargement, 5024 and 5025.
Is a latch for temporarily storing new gradation data PP0, PP2, PP4 of the pixel P0 and the pixel P2 obtained by the edge processing unit 517.

Next, the function of the edge processing section 517 will be described. FIG. 6A shows gradations of adjacent pixels before edge processing. Pixel Pa is the adjacent pixel before pixel P0, pixel Pb
Is an adjacent pixel after the pixel P4. Edge processing unit 517
Is the following equation (1) from the gradation data of the pixels P0, P2, P4
Processing is performed as in 3). That is, PP0 = s1 {s2 * P0-s3 * (Pa + P2)} + P0 PP2 = s1 {s2 * P2-s3 * (P0 + P4)} + P2 PP4 = s1 {s2 * P4-s3 * (P2 + Pb)} + P4 ... (13) ) And s1, s2, s3 are coefficients. It is set according to the degree of emphasis of edge processing. Here, for simplification, s1 = 1, s2 = 2, and s3 = 1. Therefore, the above equation (13) becomes the following equation (14). That is, PP0 = 2 * P0- (Pa + P2) + P0 PP2 = 2 * P2- (P0 + P4) + P2 PP4 = 2 * P4- (P2 + Pb) + P4 (14).

In FIG. 6, the state after the edge processing of the gradation of the pixel before the enlargement of (a) by the equation (14) is shown in (b). In this way, the interpolation processing shown in Expression (12) is performed after emphasizing the portion corresponding to the edge of the image.
The result is shown in FIG. As an effect of the above, when the image of the video signal is enlarged and the image is recorded by the copying machine, the edge portion of the image is emphasized to obtain the image, so that the enlarged image with less blur can be formed.

The present invention may be applied to either a system composed of a plurality of devices or an apparatus composed of a single device. Further, it goes without saying that the present invention can be applied to the case where it is achieved by supplying a program to a system or an apparatus.

[0034]

As described above, according to the present invention, it is possible to obtain an enlarged image while preserving the change in gradation of the image before enlargement, that is, the sharpness of the edge portion of the image.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image processing apparatus according to a first embodiment.

FIG. 2 is a diagram showing a state of gradation change of an enlarged image according to the first embodiment.

FIG. 3 is a block diagram showing a configuration of an image processing apparatus according to a second embodiment.

FIG. 4 is a diagram showing a change in gradation of adjacent interpolation pixels according to the second embodiment.

FIG. 5 is a block diagram showing a configuration of an image processing apparatus according to a third embodiment.

FIG. 6 is a diagram showing changes in gradation of adjacent interpolation pixels according to the third embodiment.

FIG. 7 is a configuration diagram showing an image processing system according to a first embodiment.

FIG. 8 is a configuration diagram showing a general image processing system.

9 is a diagram expressing an error between an NTSC composite signal input to the image processing apparatus 200 and a converted RGB signal. FIG.

FIG. 10 is a diagram illustrating an interpolation method of a general interpolation unit 207.

FIG. 11 is a block diagram showing a configuration of a general image processing apparatus.

FIG. 12 is a diagram illustrating an interpolation method according to a conventional example.

[Explanation of symbols]

 208 output unit 501 pixel counter 503 subtractor 504 divider 505 enlargement ratio 506 change rate setting unit 507 adder 511 latch 512 array unit 513 change rate determining unit 516 comparator 517 edge processing unit 2061,2062, 2063 memory 5021, 5022 latch

[Procedure amendment]

[Submission date] August 24, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

Reference numerals 2091, 2092 and 2093 denote the memory 2
D / A converters for converting the RGB digital data stored in 061, 2062, 2063 into analog values, and the D / A converters 2091, 2092, 209
3 includes a low-pass filter that removes spurious components of the sampling frequency. D / A converter 2091,
The analog RGB signals converted into analog signals by 2092 and 2093 are the D / A conversion units 2091,
Conversion errors of 2092 and 2093, and encoder 211
The error of is included. Reference numerals 2101, 1022, and 2103 are adjustment volumes provided to remove the error.
Reference numeral 211 denotes an encoder that combines an analog RGB signal with the sync signal sent from the decoder 203 to generate an NTSC composite signal, and 212 is provided to confirm an image input to the image processing apparatus 200. The switch is a switch that switches the image signal bypassed from the unit 201 and the RGB digital data, that is, the image stored in the memories 2061, 2062, and 2063, and sends the image to the monitor 3.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

The details of the interpolation unit 207 will be described. In FIG. 10, (b) and (e) are output images of the copying machine 400 when the image is not enlarged. FIG. 10A shows a state in which a part of FIG. 10C is enlarged and displayed. P0, P1, P2 and P3 are signal sources 1
It is a pixel when the NTSC composite signal output from the video signal, that is, the video signal is converted into discrete information. P
0, P1, P2, and P3 are adjacent pixels. The image horizontal direction is X and the image vertical direction is Y. xi and yi are P0
Represents the distance from. Moreover, P0, P1, P2, and P3 represent the gradation of a pixel.

Claims (2)

[Claims] 1. An image processing apparatus for enlarging an image by interpolating pixels, the detecting means detecting a change in gradation between adjacent pixels based on input discrete pixel information, and the detected floor. Adjusting means for adjusting the rate of change of the gradation of the interpolated pixel according to the degree of change of the tone; and generating means for generating pixel information corresponding to the interpolation pixel according to the rate of change adjusted by the adjusting means. An image processing device characterized by: 2. The image processing apparatus according to claim 1, wherein the discrete pixel information is data obtained by sampling and quantizing a composite image signal which changes with time.