JPH09200575A - Image data interpolation device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct proper interpolation realizing smoothness even with respect to an edge at a shallow angle by deciding an interpolation direction based on correlation between pieces of block data consisting of sets of reference picture element data. SOLUTION: A CPU reads picture element data A(-4)-A(4) and C(-4)-C(4) from a frame memory. Reference picture element data P(-8)-P(8) and Q(-8)-Q(8) are generated by interpolating image data consisting of averaged data of adjacent image data between the adjacent image data. Three consecutive reference picture element data P, Q each are used for one block and an inter-block correlation value is calculated from a sum of differences of the blocked reference picture element data with respect to k(=-7-7). The value (k) providing a minimum inter-block correlation value is decided as an optimum interpolation direction. An interpolation picture element data B(0) is obtained by calculating an equation B(0)=(P(k)+Q(-k))/2 with the value (k).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data interpolating device for displaying a high quality still image on a video tape recorder or the like, and particularly interpolating image data from a field image in interlaced scanning to generate a frame image. The present invention relates to an image data interpolating device.

[0002]

2. Description of the Related Art Conventionally, when a still image is displayed on a video tape recorder, a video printer or the like which employs an interlaced scanning method, an image in the first field is interpolated to generate a frame image, and the A high quality single still image is displayed by eliminating the time lag of the image from the second field. A conventional image data interpolation technique for interpolating the image of the first field to generate a frame image will be described with reference to FIGS.
This will be described with reference to FIG.

Here, FIG. 7 is a reference diagram showing an example of an original field image for explaining the conventional image data interpolation technique, and FIG. 8 is an original field image marked with a circle in FIG. It is an enlarged view for explaining the details of. FIG.
FIG. 10 is a diagram for explaining a method of interpolating a pixel to be interpolated by one of upper and lower pixels vertically adjacent to each other in interpolation of a field image. FIG. FIG. 11 is a diagram for explaining a method of interpolation using the average value of pixels, and FIG. 11 is a diagram for explaining a method of interpolation using the correlation of diagonal pixels of the pixels to be interpolated. FIG. 12 is a diagram for explaining interpolation in 5 directions, and FIG. 13 is a diagram for explaining interpolation in 7 directions. Furthermore, FIG. 14 and FIG. 15 are reference diagrams related to the interpolation direction determination using the correlation.

In the interlaced scanning, one frame image is divided into two field images at different times and
As the second scan fills the space between the trajectories of the second scan,
This is a scanning method in which an image is displayed by scanning in two steps.
The two images projected twice are recognized as one image due to the afterimage effect on human visual characteristics.
However, when the two field images sent in two times are directly converted into frame images to generate a still image, there is no problem if the camera and the subject are completely stationary. , The temporal shift between the field images impairs the continuity of the image between the odd and even scan lines of the image, causing There will be a gap with the image. As a result, the quality of the displayed image is deteriorated.

Therefore, it is possible to derive a frame image based on either one of the first field image and the second field image. In this case, the original field image is as shown in FIG. Since there is a space between every other scanning line, it is necessary to interpolate the image data. Various methods have been conventionally proposed as this interpolation method, some of which will be described below.
In the following description, B (0) represents pixel data to be interpolated, and A (n) and C (n) are reference pixels of the upper and lower horizontal scanning lines referred to during interpolation. Represents data. However, n is the pixel data B (0)
Represents the array element number of the pixel data on the horizontal scanning line with reference to.

The first is a method of simply repeating it. As shown in FIG. 9, the image data of each of the odd scanning lines 1, 3 ... This is a method of interpolating as image data of the scanning lines 4, .... That is, according to this method, B (0) = A (0) is interpolated. Of course, the odd scan lines may be interpolated from the even scan lines. With this method, the vertical resolution is halved, and the jagged lines become very noticeable.

Next, as shown in FIG. 10, the pixel to be interpolated may be interpolated by the average value of the reference image data of the upper and lower two pixels. That is, according to this method, interpolation is performed with B (0) = (A (0) + C (0)) / 2. With this method, the image is slightly jagged, but the image is blurred due to the deterioration of the edges.

Further, as shown in FIG. 11, paying attention to the directionality of the edge, not only in the vertical direction of the pixel to be interpolated but also in all three directions from the upper right to the lower left and from the upper left to the lower right, that direction There is also known a method of calculating the difference between the image data of two reference pixels sandwiching the pixel to be interpolated, and interpolating with the average value of the image data of the two pixels in the direction in which the difference is minimized. That is, according to this method, B (0) = (A (-1) + C (1)) / 2 B (0) = (A (0) + C (0)) / 2 B (0) = The smallest value of B (0) of (A (1) + C (-1)) / 2 is interpolated as the image data of the interpolation pixel.

However, the image also has an inclined edge that is substantially horizontal, and in this case, the above-described three-direction interpolation cannot sufficiently cope with it. Therefore, as shown in FIGS. 12 and 13, it becomes necessary to set more reference pixels on the horizontal scanning lines above and below the pixel to be interpolated to refer to pixels in, for example, 5 directions or 7 directions. However, in this case, A (-3) and C (3) shown in FIG.
Like (3) and C (-3), the further the reference pixel is from the pixel B (0) to be interpolated, the more likely it is that the pixels are not image-related and that their luminances are substantially the same. Becomes higher. Therefore, in this case, the interpolated pixel B (0) may be replaced with a completely different value which is discontinuous from the adjacent pixel, and appears as extremely noticeable noise on the image.

As an improved version of the conventional image data interpolation technique, the one disclosed in Japanese Patent Laid-Open No. 153562/1993 is known. This image data interpolation technique assumes interpolation in 7 directions as shown in FIG. 13. First, the interpolation is performed by the six reference pixels, and in FIG.
1) and C (1), A (0) and C (0), A (1) and C
The correlation is determined for each direction with (-1) as the first region. Then, when there is a correlation between the diagonal direction in the first region, that is, A (-1) and C (1) or A (1) and C (-1), the correlation is determined even at a shallower angle. . That is, if it is determined that there is a correlation between A (1) and C (-1) at the first stage, A (1)
And C (-1), A (2) and C (-2), A (3) and C
The correlation is determined for each of the regions (-3) as the second region. On the other hand, if it is determined that A (-1) and C (1) have correlation, A (-1) and C ( 1), A (-2)
And C (2) and A (-3) and C (3) are used as the third regions to determine the correlation, and the one having the strongest correlation is determined to determine the interpolated pixel data.

[0011]

However, according to these conventional image data interpolation techniques, accurate interpolation may not always be performed, and the resulting interpolated image may have irregularities in the originally smooth contour line. Occurrence of noise due to interpolation errors is often observed (incorrect interpolation is performed, and pixels interpolated in this way are
Hereinafter referred to as "interpolation error"). First of all,
It can be mentioned that the edges of the image do not always lie along the actual pixels. For example, consider the case where B (0) is interpolated in the image shown in FIG. In this case, the straight line L is C from the boundary between A (0) and A (1).
A crossing the boundary between (-1) and C (0)
It is assumed that exactly the same image data points exist in (3) and C (-3). An image in such a state is sufficiently possible when an NTSC television image or the like whose resolution is not higher than that of printing is digitized and handled.

Here, A (0), A (1), C (-
1) and C (0) pixel data are 5, 5, 6, and
3, while the image data of A (3) and C (-3) is x
And It is also assumed that the correlation with other reference pixels is low. In such a case, the difference value between A (0) and C (0) is 2, the difference value between A (1) and C (-1) is 1, and A (3) is There is a possibility that the calculated value will be larger than the difference value from C (−3). That is, in this case, A (0) and C
It is determined that the correlation with (0) and the correlation between A (1) and C (-1) are smaller than the correlation between A (3) and C (-3), and as a result, B (0) is , Correlation is not necessarily high A
There is a problem that interpolation is performed by the average value of the image data of (3) and C (-3). In addition, the above-mentioned Japanese Patent Laid-Open No. 5-1
The method of Japanese Patent No. 53562 also has the same problem because it is determined as a diagonal line in the determination in the first step.

Secondly, according to the method disclosed in Japanese Patent Laid-Open No. 5-153562, contrary to the first example, A (3)
Even if it is correct to interpolate with C (-3),
There is a case in which interpolation is erroneously performed using A (0) and C (0). That is, according to this method, A (0) and C shown in FIG.
(0), A (-1) and C (1), A (1) and C (-1)
When the diagonal correlation is not detected in the three-direction correlation in the first region, the correlations in the second and third regions are not examined. Therefore, in the case of an edge having a shallow angle, there is a problem that it may not be adopted as a reference pixel for generating interpolated pixel data although the correlation between A (-3) and C (3) is strongest. there were.

The present invention has been made in view of the above problems, and performs appropriate interpolation for realizing smoothness even for an edge having a shallow angle, and further eliminates noise generated by an interpolation error after this interpolation. An object of the present invention is to provide an image data interpolating device capable of synthesizing high-quality frame image data from one piece of field image data by suppressing the occurrence of interpolation error as much as possible by detecting and removing it.

[0015]

In order to solve the above problems, the present invention has the following constitution. The image data interpolating apparatus according to claim 1, wherein the field data forming pixel data corresponding to pixels on one of the odd-numbered or even-numbered scanning lines of the frame data scans the other of the odd-numbered or even-numbered scans of the frame data. In an image data interpolating device that generates interpolating pixel data corresponding to interpolating pixels on a line to generate the frame data, the image data interpolating device determines an interpolation direction from the interpolation pixel as a starting point, and is positioned in the interpolation direction. Interpolating the field data to generate frame data by generating interpolated pixel data corresponding to the interpolated pixel based on the pixel data, and the one scan adjacent to the upper side of the interpolated pixel. Interpolating a column of pixel data corresponding to a column of pixels on the line to generate a first column of reference pixel data, and Serial and reference pixel data generating means for generating a sequence of second reference pixel data by interpolating a row of pixel data corresponding to the columns of pixels of the one scan line adjacent to the lower side of the interpolated pixel,
The first block data composed of a set of consecutive predetermined number of reference pixel data forming a column of the first reference pixel data and the interpolated pixel data are sandwiched between the first block data and the second block data. Interpolation direction determining means for determining the interpolation direction of the interpolation pixel based on the calculation result of the correlation with the second block data formed of a set of continuous predetermined number of reference pixel data forming the column of the reference image data of , The interpolation pixel data is generated based on pixel data corresponding to pixels on the one scanning line located in the interpolation direction determined by the interpolation direction determining means and adjacent to the upper side and the lower side of the interpolation pixel. And interpolation pixel data generation means.

According to another aspect of the image data interpolating apparatus of the present invention, from the field data forming the pixel data corresponding to the pixel on the odd-numbered or even-numbered scanning line of the frame data, the odd-numbered or even-numbered field data of the frame data is selected. In an image data interpolating device that generates interpolating pixel data corresponding to an interpolating pixel on the other scanning line to generate the frame data, the image data interpolating device determines an interpolating direction starting from the interpolating pixel, and the interpolating direction Interpolating the field data to generate frame data by generating interpolated pixel data corresponding to the interpolated pixel based on the pixel data located in the interpolated pixel data and the interpolated pixel data and the interpolated pixel data. Based on comparison with pixel data located adjacent to or near the interpolated pixel data. Determination means for determining the correctness of the data, and a correction generated from the pixel data of pixels located adjacent to the interpolation pixel data or in the vicinity of the interpolation pixel data based on the result of the determination by the determination means. Correlation value correcting means for correcting the interpolated pixel data by replacing it with data.

According to a third aspect of the present invention, the image data interpolating apparatus is configured such that the interpolation direction determining means of the image data interpolating apparatus according to the first aspect calculates the correlation by weighting based on the interpolation direction. There is.

In the image data interpolating device according to the fourth aspect, the determining means of the image data interpolating device according to the second aspect uses the second derivative or the eight-direction Laplacian to interpolate the pixel data and the adjacent pixel data. The interpolation pixel data is configured to be compared with pixel data located in the vicinity.

According to the image data interpolating device of the first or third aspect, the reference data generating means, for example, obtains an average value of these average values between adjacent pixel data on the scanning line adjacent to the upper side of the interpolation pixel. The first reference pixel data row is generated by adding the obtained data, and the average of these values is added between the adjacent pixel data on the scanning line adjacent to the lower side of the interpolation pixel. A second row of reference pixel data is generated to increase the number of horizontal reference pixel data. Next, the interpolation direction determining means interpolates the correlation between the first block data on the upper scanning line of the interpolation pixel and the second block data on the lower scanning line on the extension line of the interpolation pixel. The optimum interpolation direction is determined by calculating the direction and weighting the calculation result according to the interpolation direction.
The interpolation pixel data generation means generates the interpolation pixel data of the interpolation pixel by using the pixel data located in the determined interpolation direction.

According to the image data interpolating device of the second and fourth aspects, the determining means uses the second derivative or the eight-direction Laplacian to interpolate the pixel data and the periphery (adjacent or neighboring) of the pixel of the interpolating pixel data. ) And the pixel data of the pixel located at () to determine the validity (interpolation error).
If the result of this determination is that the interpolated pixel data is not valid, the correlation value correction means re-interpolates by generating correction data from the pixel data of the peripheral pixels of the interpolated pixel and replacing the interpolated pixel data with this correction data.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image data interpolating apparatus and an interpolating method according to an embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a block diagram showing the configuration of an image data interpolating apparatus according to an embodiment of the present invention.
2 is an image data array diagram showing an array of pixel data of pixels around the pixel to be interpolated, and FIG.
FIG. 4 is an explanatory diagram for explaining a horizontal direction interpolation process for obtaining reference image data from the image data shown in FIG. 2. Further, FIG. 4 is an explanatory diagram for explaining a method of calculating a correlation value from the reference image data shown in FIG. 3, and FIG.
[Fig. 6] is an explanatory diagram for explaining an interpolation error of image data. Furthermore, FIG. 6 is a flowchart for explaining the flow of the interpolation processing in the present invention.

[0022] First, as shown in FIG. 1, the image data interpolating apparatus according to this embodiment receives the input video signal P _i, to generate the image data D to the input video signal P _i and digitizing A / A D converter 101, a frame memory 102 for storing one frame of image data D obtained by digitization by the A / D converter 101, and a frame memory 102 controlled by a controller described later.
Image data D transferred from the D / A converter 103 to generate an output video signal P _O , and the A / D converters 101 and D / D under the control of the CPU described later.
A controller 104 that controls the operations of the A converter 103 and the frame memory 102, and an A / D converter 1
The CPU 105 is configured to include a correlation calculation process of the image data D digitized by 01 and stored in the frame memory 102, and control the operations of the frame memory 102 and the controller 104. Here, description will be made assuming luminance data as the image data D obtained by digitizing the input video signal P _i . The CPU 105 has a built-in RAM for storing correlation calculation data and a ROM storing a control program.

The operation and the interpolation method of the image data interpolating apparatus according to the present embodiment thus configured will be described below with reference to FIGS. 1 to 6. This image data interpolating device calculates "..., i-" from the pixel data of the row of "..., i-1, i + 1, ..." in one field image that already exists.
2, i, i + 2, ... ”, and the pixel data of the row is generated,
For simplification of description, a case of generating and interpolating pixel data (hereinafter, referred to as interpolated pixel data) B (0) of a pixel (hereinafter, referred to as interpolated pixel) in the i-th row and j-th column shown in FIG. A description will be given according to the flowchart shown in FIG.

First, in FIG. 1, the input video signal P _i is converted into image data D which is digital data by the A / D converter 101. Of the image data D obtained by conversion, the image data D for one frame
However, the frame memory 1 is controlled by the controller 104.
02 is input. The frame memory 102 stores the pixel data forming the first field in the input image data for one frame in an odd row address and the image data forming the second field in an even row address.

Next, the CPU 105 shown in FIG. 1 reads out the pixel data A (-4) to A (4) of the (i-1) th row shown in FIG. 2 from the frame memory 102. Then, as shown in FIG. 3, the image data composed of the average value of the adjacent image data is interpolated to obtain the reference pixel data P.
(-8) to P (8) are newly generated. Similarly, from the pixel data C (-4) to C (4), the reference pixel data Q (-
8) to Q (8) are generated (step S1).

That is, P (k) = A (k / 2) (k = -8, -6, -4, -2,0,2,4,6,8) P (k) = (A (( k-1) / 2) + A ((k + 1) / 2)) / 2 (k = -7, -5, -3, -1,1,3,5,7) Q (k) = C (k / 2) (k = -8, -6, -4, -2,0,2,4,6,8) Q (k) = (C ((k-1) / 2) + C (( k + 1) / 2)) / 2 (k = -7, -5, -3, -1,1,3,5,7) is calculated and stored in the RAM inside the CPU 105. Less than,
Pixel data A (-4) to A (4) and C (-4) to C
The process of generating the reference pixel data P (-8) to P (8) and Q (-8) to Q (8) from (4) is referred to as horizontal direction interpolation process.

Next, as shown in FIG. 4, the reference pixel data P (•) and Q (•) obtained by the horizontal direction interpolation processing are made into three consecutive image data as one block, respectively. The inter-block correlation value S (k) is calculated for each k from the sum of differences of the reference pixel data delimited by (step S2). That is, S (k) = | P (k-1) -Q (-k-1) | + | P (k) -Q (-k) | + | P (k + 1) + Q (-k + 1) | (k = -7, -6, -5, -4, -3, -2, -1,0,1,2,3,4,5,6,7) The correlation value S (k) is calculated.

For this inter-block correlation value S (k), T (k) = α (k) S (k) + β (k) (k = -7, -6, -5, -4, -3, -2, -1,0,1,2,3,4,5,6,7) to obtain a corrected inter-block correlation value T (k) (step S3). The correction block correlation value T
The value k that gives the minimum value of (k) is determined as the optimum interpolation direction (step S4). Here, the inter-block correlation value S
The correction coefficients α (k) and β (k) introduced in the process of obtaining the corrected inter-block correlation value T (k) from (k) are correction values that increase with an increase in the absolute value of k. Therefore, when two or more inter-block correlation values S (k) with different k are equal to each other or have a slight difference, the vertical direction, that is, k closer to 0 is preferentially adopted to determine the interpolation direction.

The inter-block correlation value S (k) obtained by dividing the reference pixel data into blocks of three is much smaller than the correlation value obtained by comparing each pixel. growing. Therefore, the correction coefficient α
Even if the correction coefficient is determined by (k) and β (k) so as to give priority to the interpolation in the vertical direction, the interpolation direction in the diagonal direction is appropriately selected, and the interpolation in the shallow diagonal direction is also appropriately performed. Note that the number of reference pixel data that is divided into blocks when calculating the inter-block correlation value S (k) is not limited to three, and an appropriate number may be set as necessary.

B (0) = (P (k) + Q (-k)) / 2 is calculated using k which gives the optimum interpolation direction thus obtained, and the interpolated pixel data B (0) is calculated. Get (step S5). Then, the interpolation pixel data value B (0) is stored in a predetermined address of the frame memory 102 corresponding to the interpolation pixel in the i-th row and the j-th column shown in FIG. 2 (step S).
6).

Similarly, the pixel to be processed is moved, the interpolated pixel data is sequentially and repeatedly obtained for all the pixels in the i-th row shown in FIG.
Is stored in a corresponding predetermined address of 1 to obtain interpolated pixel data for one row (step S7 to step S8 to step S1 to step S7). Here, the frame memory 10 for the pixel data A (•) and C (•) necessary for interpolation
The reading from 2 and the horizontal direction interpolation process may be performed as much as newly required due to the movement of the pixel to be processed.

Now, even with respect to the frame images obtained by the above interpolation processing (steps S1 to S8), the interpolation result cannot be said to be 100% valid, and a slight interpolation error may occur. Therefore, next, a process of correcting a slight interpolation error that may occur (hereinafter, referred to as a correction process) will be described. This correction processing includes a step of detecting and determining image data of pixels interpolated due to an interpolation error (step S9) and a step of replacing image data in which an interpolation error is detected with valid interpolation data (step S10). Become.

First, the step of detecting the interpolated pixel data generated by the interpolation error will be described. Normally, an image captured by a visual sensor such as a camera is displayed on the boundary with surrounding pixels even if the subject has a fine polka dot pattern due to the characteristics of the optical system of the visual sensor and the characteristics of the image sensor. There is some blurring. However, when an interpolation error occurs, the boundary is synthetically generated by the interpolation process, and therefore has the characteristic of being extremely clear.
The correction process described below focuses on this feature and detects the presence or absence of this feature to determine whether or not an interpolation error has occurred.

Now, assuming that the interpolated pixel data B (0) at the i-th row and j-th column of the pixel data array shown in FIG. 5 is the pixel data generated by the interpolation error, this interpolated pixel data B
Consider a case where (0) is corrected. In the figure, the pixel data of the i-th row is obtained by the interpolation process, and the correction process described below is performed only on the pixel data of the line obtained by the interpolation process.

The CPU 105 shown in FIG. 1 stores the pixel data A (-1) to A shown in FIG.
(1), B (-1) to B (1), and C (-1) to C
(1) is read out and the evaluation value d is calculated from the following arithmetic expression. d = | -A (0) + 2 * B (0) -C (0) | * | -B (-1) + 2 * B (0) -B (1) | * |
-A (-1) + 2 * B (0) + C (1) | * | -A (1) + 2 * B (0) + C (-1) | where the evaluation value d is the vertical direction , The horizontal direction, the diagonally upper left to the diagonally lower right, and the diagonally right to the diagonal lower left are respectively calculated, and the secondary differentials are calculated and the absolute values thereof are multiplied, and the interpolated pixel data B (0) is Represents the degree of isolation from the pixel data of the pixel.

In general, as shown in FIG. 5, when an interpolation error occurs, the image level is significantly different from the surrounding pixels. In this case, since the evaluation value d shows an extremely large value, it can be considered that the pixel data whose evaluation value d exceeds a predetermined threshold value is generated by an interpolation error. Easily judge the correctness of data (hereinafter referred to as interpolation correctness judgment)
Can be performed (step S9). In addition, even if the detection ability of the interpolation error is slightly lowered, the evaluation value d is d = | 8 * B (0) -A (-1) -A (0) -A (1) -B (-1)- B (1) -C (-1) -C (0)-
An eight-way Laplacian may be used, such as C (1) |.

Next, if an interpolation error is detected in the interpolation correctness determination and it is determined that the interpolation is not correct, the interpolation pixel data in which the interpolation error is detected is replaced with vertical image data (step S10). That is, the interpolation image data of the interpolation pixel in which the interpolation error is detected is replaced with the interpolation data obtained by B (0) = (A (0) + C (0)) / 2. In this case, the interpolation data is the average value of the pixel data that is vertically adjacent to the interpolation pixel in which the interpolation error is detected.

Similarly, by performing correction processing (steps S9 to S10) on all pixel data of the i-th row shown in FIG. 2 generated by the interpolation processing,
One row of pixel data in which the interpolation error generated in the interpolation processing (steps S1 to S8) is corrected is obtained. Further, similarly, the above-described interpolation processing and correction processing are repeatedly performed for each row to be interpolated, and finally image data for one frame is generated from the image data for one field and is stored in the frame memory 102. Given. As a result, the frame memory 102 stores the image data for one frame in which the interpolation error is corrected and the noise is inconspicuous.

When one frame of image data is obtained by a series of image data interpolation processing consisting of interpolation processing and correction processing, the CPU 105 controls the frame memory 102 and the D / A converter 103 via the controller 104, The image data for one frame stored in the memory 102 is converted into an output video signal P _O by the D / A converter 103 and output from this device to the outside.

In the correction processing described above, the interpolation processing and the correction processing are repeated for each row to process the interpolated image data for one field. However, the interpolation processing is performed for all pixel data for one field. After performing the processing, the correction processing may be collectively performed, or the correction processing may be omitted if an image of sufficient quality can be obtained by the interpolation processing.

Further, in the horizontal direction interpolation processing for generating the reference pixel data used for the interpolation processing from the pixel data,
The reference pixel data was prepared by interpolating the data between the adjacent pixel data with the average value of these adjacent pixel data, but the number of data for interpolating the pixel data in this horizontal direction interpolation processing is increased to any number. The reference pixel data P (.) And Q may be used for simplification of the processing.
Pixel data A directly without preparing (・)
The interpolation direction may be obtained by performing similar processing on (•) and C (•).

Further, the CPU 105 constituting the image data correction apparatus of this embodiment executes the correlation calculation and the like according to the program stored in the internal ROM, but the essence of the present invention is the calculation. It is not restricted by the means of execution. That is, this calculation process may be realized by other hardware, or the same interpolation process may be entirely executed by software by a personal computer or a workstation.

Further, in the description of the present embodiment, the luminance data is assumed as the image data, but when the color image is subjected to the interpolation processing for the color difference signal, the same as the interpolation direction obtained by processing the luminance data. The interpolation process may be performed with reference to the direction data.

According to the image data interpolating apparatus of the present embodiment described above, P (•) and Q (•) obtained by interpolating with the average value of adjacent pixel data are prepared as reference pixel data and interpolated. Since the direction is determined, the possibility that the pixel data unrelated to the actual edge is erroneously interpolated as the reference pixel data is reduced. Further, since the state of the pixels around the pixel to be interpolated is reflected for each block composed of three adjacent pixel data, the correlation is obtained.
Interpolation errors are reduced as compared with the case where the correlation is simply obtained from the difference between two vertically adjacent pixels.

Further, according to the image data correction apparatus of the present embodiment, the interpolation direction is obtained from the evaluation function T (k) which is corrected so that the vertical direction is prioritized, so that the correlation is recognized in any direction. If not, or if the difference value in the valid interpolation direction shows a minimum value even though it is not the valid interpolation direction, the probability of vertical interpolation is high, and it becomes closer. Since the interpolation is performed by referring to the pixel data of the pixel, the occurrence of interpolation error is reduced.

Further, according to the image data correction apparatus of this embodiment, the D / A converter 103 is connected to the rear of the frame memory 102 and functions as a still image display apparatus. If a printer engine is connected instead of, a video printer capable of high-quality printing can be realized.

[0047]

According to the present invention as described above, the following effects can be obtained. That is, according to the first aspect of the invention, since the interpolation direction is determined from the correlation value of the two blocks of the reference pixel data that face each other with the interpolation pixel in between, the accurate interpolation direction can be determined, and the interpolation process can be performed. Interpolation errors can be significantly reduced.

According to the second aspect of the present invention, the pixel data generated by the interpolation error is detected and replaced with the interpolation data generated from the pixel data located in the periphery (adjacent or near) of this pixel data. Therefore, it is possible to virtually eliminate visual noise due to an interpolation error generated in the interpolation process.

Furthermore, according to the third aspect of the present invention, the correlation is determined by weighting based on the interpolation direction, and the interpolation is performed based on this determination, so there is little unevenness even for edges with a shallow angle. , Smooth interpolation can be realized.

Further, according to the invention of claim 4, in determining the interpolation error of the pixel data obtained by the interpolation processing, the pixel data obtained by the interpolation using the second derivative or the eight-direction Laplacian is used. Since the evaluation value representing the isolation is calculated and judged, this evaluation value shows an extremely large value with respect to the interpolation error, and the interpolation error can be easily determined.

Therefore, according to the present invention as set forth in claims 1 to 4, the number of interpolation errors is extremely small and the visual noise caused by the interpolation errors can be virtually eliminated. It is possible to obtain still image frame data of extremely high quality.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image data interpolation device according to an exemplary embodiment of the present invention.

FIG. 2 is a pixel array diagram showing an array of peripheral pixels centered on a pixel interpolated by the image data interpolating apparatus according to the embodiment of the present invention.

FIG. 3 is a diagram for explaining generation of reference pixel data by the image data interpolating device according to the embodiment of the present invention.

FIG. 4 is an explanatory diagram for explaining a method of calculating a correlation value by the image data interpolation device according to the exemplary embodiment of the present invention.

FIG. 5 is an explanatory diagram for explaining an interpolation error by the image data interpolation device according to the embodiment of the present invention.

FIG. 6 is a flowchart for explaining a flow of interpolation processing and correction processing by the image data interpolation device according to the embodiment of the present invention.

FIG. 7 is a reference diagram showing an original field image for explaining a conventional technique.

FIG. 8 is an explanatory diagram for explaining details of an original field image for explaining a conventional technique.

FIG. 9 is an explanatory diagram for explaining a conventional interpolation method of interpolating a pixel to be interpolated by one of vertically adjacent pixels.

FIG. 10 is an explanatory diagram for explaining a conventional interpolation method of interpolating a pixel to be interpolated with an average value of vertically adjacent pixels.

FIG. 11 is an explanatory diagram for explaining a conventional interpolation method of performing interpolation by using the correlation of diagonal pixels of the pixel to be interpolated.

FIG. 12 is an explanatory diagram for describing interpolation in five directions.

FIG. 13 is an explanatory diagram for describing interpolation in seven directions.

FIG. 14 is a reference diagram related to interpolation direction determination using correlation.

FIG. 15 is a reference diagram relating to interpolation direction determination using correlation.

[Explanation of symbols]

 101 A / D converter 102 Frame memory 103 D / A converter 104 Controller 105 CPU

Claims (4)

[Claims] 1. A field data forming pixel data corresponding to a pixel on one of odd-numbered or even-numbered scanning lines of frame data and corresponding to an interpolated pixel on another odd-numbered or even-numbered scanning line of frame data. In the image data interpolating device that generates the interpolated pixel data to generate the frame data, the image data interpolating device determines an interpolating direction from the interpolating pixel as a starting point, and based on the pixel data located in the interpolating direction. By generating interpolated pixel data corresponding to the interpolated pixel, the field data is interpolated to generate frame data, and a frame of pixels on the one scanning line adjacent to the upper side of the interpolated pixel is formed. A column of the corresponding pixel data is interpolated to generate a column of the first reference pixel data, and is adjacent to the lower side of the interpolation pixel. A reference pixel data generation unit that interpolates a column of pixel data corresponding to a column of pixels on the one scanning line to generate a second column of reference pixel data, and a column of the first reference pixel data. The first block data consisting of a set of a predetermined number of continuous reference pixel data and the interpolated pixel data are sandwiched between the first block data and the second block of the reference image data. Interpolation direction determining means for determining an interpolation direction of the interpolation pixel based on a calculation result of a correlation with a second block data composed of a set of a predetermined number of reference pixel data; and the interpolation direction determining means defined by the interpolation direction determining means. An interpolation image for generating the interpolation pixel data based on pixel data corresponding to pixels on the one scanning line located in the interpolation direction and adjacent to the upper side and the lower side of the interpolation pixel. An image data interpolating device comprising: a raw data generating unit. 2. A field data forming pixel data corresponding to a pixel on one of odd-numbered or even-numbered scanning lines of frame data and corresponding to an interpolated pixel on another odd-numbered or even-numbered scanning line of the frame data. In the image data interpolating device that generates the interpolated pixel data to generate the frame data, the image data interpolating device determines an interpolating direction from the interpolating pixel as a starting point, and based on the pixel data located in the interpolating direction. Interpolating the field data to generate frame data by generating interpolation pixel data corresponding to the interpolation pixel, the interpolation pixel data being adjacent to the interpolation pixel data or in the vicinity of the interpolation pixel data. Determination means for determining the validity of the interpolation data based on the comparison with the pixel data located at Correcting the interpolated pixel data by replacing the interpolated pixel data with correction data generated from pixel data of a pixel adjacent to the interpolated pixel data or in the vicinity of the interpolated pixel data, based on the result of the judgment by the judgment means. An image data interpolating device, comprising: a correlation value correcting means. 3. The image data interpolating apparatus according to claim 1, wherein the interpolation direction determining means calculates the correlation by weighting based on the interpolation direction. 4. The determining means compares the interpolated pixel data with pixel data located adjacent to the interpolated pixel data or in the vicinity of the interpolated pixel data by using a second derivative or eight-direction Laplacian. The image data interpolation device according to claim 2.