Image processing device, image processing method and program

Abstract

This image processing device comprises: an assessment unit for assessing whether, among a plurality of pixels arranged linearly in a row including a pixel of interest, a first adjacent pixel, and a second adjacent pixel, there exists a pixel having a pixel value for which the difference from the pixel value of the pixel of interest is greater than or equal to a reference value; a grayscale level difference assessment unit for assessing whether or not the difference between the average value of pixel values of a first pixel group and the average value of pixel values of a second pixel group is less than or equal to a first threshold value when it is assessed by the assessment unit that there exist no pixels having a pixel value for which the difference from the pixel value of the pixel of interest is greater than or equal to the reference value; and a correction unit for correcting the grayscale level difference of at least one pixel among the plurality of pixels when it is assessed by the grayscale level difference assessment unit that the difference between the average value of pixel values of the first pixel group and the average value of pixel values of the second pixel group is less than or equal to the first threshold value.

Description

[Technical field]

[0001] The present disclosure relates to an image processing device, an image processing method, and a program. [Background technology]

[0002] Techniques have been disclosed for reducing gradation gaps that occur in gradation areas in a displayed image due to roughness in quantization of a video signal. For example, Patent Document 1 discloses a technique for making gradation gaps less noticeable by smoothing processing. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 4874184 Summary of the Invention

[0004] However, the technique disclosed in Patent Document 1 has a problem in that even areas that are not tone steps are smoothed, reducing the sharpness of the areas that are not tone steps.

[0005] The present disclosure provides an image processing device and the like that can reduce tone steps while suppressing a decrease in sharpness in areas that do not have tone steps.

[0006] The image processing device of the present disclosure includes a determination unit that determines whether or not there is a pixel among a plurality of pixels arranged in a line including a pixel of interest, a first adjacent pixel adjacent to the pixel of interest, and a second adjacent pixel adjacent to the pixel of interest and opposite the first adjacent pixel, the pixel having a pixel value that differs from the pixel value of the pixel of interest by a reference value or more; when the determination unit determines that there is no pixel having a pixel value that differs from the pixel value of the pixel of interest by the reference value or more, the image processing device includes a determination unit that determines whether or not a difference between an average pixel value of a first pixel group including the first adjacent pixel among the plurality of pixels and an average pixel value of a second pixel group including the second adjacent pixel among the plurality of pixels is equal to or less than a first threshold value; and when the gradation step determination unit determines that the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than the first threshold value, the image processing device includes a determination unit that corrects a gradation step of at least one pixel among the plurality of pixels.

[0007] The image processing method disclosed herein determines whether or not there are any pixels among a plurality of pixels arranged in a line including a pixel of interest, a first adjacent pixel adjacent to the pixel of interest, and a second adjacent pixel adjacent to the pixel of interest and opposite the first adjacent pixel, having a pixel value whose difference from the pixel value of the pixel of interest is equal to or greater than a reference value; if it is determined that there are no pixels having a pixel value whose difference from the pixel value of the pixel of interest is equal to or greater than the reference value, it determines whether or not a difference between an average pixel value of a first pixel group including the first adjacent pixel among the plurality of pixels and an average pixel value of a second pixel group including the second adjacent pixel among the plurality of pixels is equal to or less than a first threshold value; and if it is determined that the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than the first threshold value, corrects a gradation step of at least one pixel among the plurality of pixels.

[0008] A program in the present disclosure is a program for causing a computer to execute the image processing method described above.

[0009] According to the image processing device and the like of the present disclosure, it is possible to reduce tone steps while suppressing a decrease in sharpness in areas that do not have tone steps. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of a configuration of an image processing device according to an embodiment. [Diagram 2] FIG. 2 is a flowchart illustrating an example of the operation of the image processing device according to the embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of pixels arranged in the horizontal direction. [Figure 4] FIG. 4 is a diagram showing an example of pixels arranged in the vertical direction. [Diagram 5] FIG. 5 is a diagram showing an example of pixels arranged in a diagonal direction. [Figure 6] FIG. 6 is a flowchart showing an example of an image processing method according to another embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed explanation than necessary may be omitted. For example, detailed explanation of already well-known matters or duplicate explanation of substantially the same configuration may be omitted. This is to avoid the following explanation becoming unnecessarily redundant and to facilitate understanding by those skilled in the art.

[0012] The inventor provides the accompanying drawings and the following description so that those skilled in the art can fully understand the present disclosure, and does not intend for them to limit the subject matter described in the claims.

[0013] (Embodiment) Hereinafter, an embodiment will be described with reference to FIG. 1 to FIG.

[0014] FIG. 1 is a diagram showing an example of a configuration of an image processing device 100 according to an embodiment.

[0015] The image processing device 100 is a device for reducing gradation steps that occur in a gradation area in a displayed image due to roughness of quantization of an input video signal (e.g., RGB signal). Gradation steps are contour stripes that occur in a gradation area, and are also called tone jumps, banding, gradation jumps, gradation steps, or gradation skips.

[0016] The image processing device 100 is a computer having a processor, a memory, etc. The memory is a ROM (Read Only Memory) and a RAM (Random Access Memory), etc., and can store a program executed by the processor. The image processing device 100 includes a judgment unit 10, a gradation step judgment unit 20, a correction unit 30, and a memory 40. The judgment unit 10, the gradation step judgment unit 20, and the correction unit 30 are realized by a processor or the like that executes a program stored in the memory. The memory 40 may be the same memory as the memory in which the program is stored, or may be a different memory.

[0017] The memory 40 is, for example, a line memory, and stores pixel values ​​(also called luminance values) of pixels for each horizontal or vertical line of a video signal input to the image processing device 100.

[0018] The determination unit 10 determines whether or not there is a pixel whose pixel value is greater than or equal to a reference value (specifically, the absolute value of the difference) from the pixel value of the pixel of interest among a plurality of pixels arranged on a straight line including the pixel of interest and within a predetermined range from the pixel of interest. For example, the determination unit 10 performs the above determination by treating each of the pixels arranged in the horizontal direction input to the image processing device 100 as the pixel of interest, and by treating each of the pixels arranged in the vertical direction input to the image processing device 100 as the pixel of interest. The above determination is performed for each of R, G, and B. The determination unit 10 has a first determination unit 11 and a second determination unit 12, and the above determination of the determination unit 10 is performed by the first determination unit 11 and the second determination unit 12. Details of the first determination unit 11 and the second determination unit 12 will be described later.

[0019] When it is determined that there is no pixel whose pixel value is greater than or equal to the reference value, the gradation step determination unit 20 determines whether or not the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is less than or equal to the first threshold value for a first pixel group and a second pixel group adjacent to each other with the pixel of interest as a boundary, in a plurality of pixels arranged on a line. In the following, an example in which the first threshold value is smaller than the reference value will be described, but the first threshold value may be greater than or equal to the reference value. For example, the gradation step determination unit 20 performs the above determination by using each of the pixels arranged in the horizontal direction input to the image processing device 100 as the pixel of interest, and performs the above determination by using each of the pixels arranged in the vertical direction input to the image processing device 100 as the pixel of interest. The above determination is performed for each of R, G, and B. Details of the gradation step determination unit 20 will be described later.

[0020] When it is determined that the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than the first threshold value, the correction unit 30 performs a correction process to correct tone steps for a plurality of pixels including the pixel of interest. Note that correcting tone steps for a plurality of pixels including the pixel of interest does not necessarily mean that all of the plurality of pixels are corrected, but means that at least one pixel included in the plurality of pixels can be corrected. For example, the correction unit 30 performs the above correction process on each of the pixels arranged in the horizontal direction input to the image processing device 100 as a pixel of interest, and performs the above correction process on each of the pixels arranged in the vertical direction input to the image processing device 100 as a pixel of interest. The correction process is performed for each of R, G, and B. Details of the correction unit 30 will be described later.

[0021] Next, the operation of the image processing device 100 will be described with reference to FIG.

[0022] FIG. 2 is a flowchart showing an example of the operation of the image processing device 100 according to the embodiment.

[0023] First, the image processing device 100 selects pixels aligned in the horizontal direction as a pixel of interest (step S10). For example, when the resolution is 1920×1080, the image processing device 100 selects one pixel as a pixel of interest from among 1920 pixels aligned in the horizontal direction.

[0024] In steps S11 and S12, the judgment unit 10 judges whether or not there is a pixel whose pixel value is greater than or equal to a reference value among pixels within a predetermined range from the pixel of interest in a plurality of pixels (pixels aligned in the horizontal direction) aligned on a straight line including the pixel of interest. For example, the pixels within the predetermined range from the pixel of interest include pixels adjacent to the pixel of interest in a plurality of pixels aligned on a straight line. The reference value includes a second threshold value and a third threshold value. In the following, an example in which the third threshold value is equal to the reference value and smaller than the second threshold value will be described. That is, an example in which the second threshold value is greater than the reference value will be described. However, the third threshold value may be greater than or equal to the second threshold value. The third threshold value may be a value different from the reference value.

[0025] The first determination unit 11 determines whether or not a contour exists around the selected pixel of interest (step S11). Specifically, the first determination unit 11 determines whether or not there exists a pixel whose pixel value differs from the pixel value of the pixel of interest by a second threshold value or more among pixels adjacent to the pixel of interest. The determination by the first determination unit 11 for pixels arranged in the horizontal direction will be described with reference to FIG. 3.

[0026] FIG. 3 is a diagram showing an example of pixels arranged in the horizontal direction.

[0027] FIG. 3 shows pixels p0 to p12 among a plurality of pixels (pixels aligned in the horizontal direction) aligned on a straight line including the pixel of interest. For example, pixel p6 is the pixel of interest, and pixels p0 to p5 and pixels p7 to p12 are pixels within a predetermined range from the pixel of interest p6. Here, the pixels within the predetermined range are pixels within a range of six pixels on the straight line from the pixel of interest p6. Note that the pixels within the predetermined range from the pixel of interest p6 need only include at least pixels adjacent to the pixel of interest p6, and the size of the predetermined range is not particularly limited. As described above, the pixels p0 to p12 aligned in a straight line include the pixel of interest p6, pixel p5 adjacent to the pixel of interest p6 (an example of a first adjacent pixel), and pixel p7 adjacent to the pixel of interest p6 and opposite the pixel p5 (an example of a second adjacent pixel).

[0028] The first determination unit 11 determines whether or not there is a pixel among pixels p5 and p7 adjacent to the pixel of interest p6 whose pixel value differs from the pixel value of the pixel of interest p6 by a second threshold value or more. The second threshold value is a threshold value for determining whether or not there is a pixel value difference between the pixels p5 and p7 adjacent to the pixel of interest p6 that is greater than a gradation step (e.g., a contour exists). For example, a portion with a contour has a pixel value difference greater than a portion with a gradation step, so the second threshold value is greater than the first threshold value for determining whether or not a gradation step exists.

[0029] If the first determination unit 11 determines that a contour exists around the selected pixel of interest (Yes in step S11), the processes in steps S13 and S14 are not performed.

[0030] If the first judgment unit 11 judges that there is no contour around the selected pixel of interest (No in step S11), the second judgment unit 12 judges whether or not there is a character, pattern, or the like around the selected pixel of interest (step S12). Specifically, the second judgment unit 12 judges whether or not there is a pixel within a predetermined range whose pixel value differs from the pixel value of the pixel of interest by a third threshold value or more. The judgment by the second judgment unit 12 for pixels aligned in the horizontal direction will be described with reference to FIG. 3.

[0031] The second determination unit 12 determines whether or not there is a pixel whose pixel value differs from the pixel value of the pixel of interest p6 by a third threshold or more among the pixels p0 to p5 and pixels p7 to p12 within a predetermined range from the pixel of interest p6. The third threshold is a threshold for determining whether or not there is a pixel value difference greater than a gradation step (for example, the presence of a character or a pattern) among the pixels p0 to p5 and pixels p7 to p12 within a predetermined range from the pixel of interest p6. For example, a portion with a character or a pattern has a pixel value difference greater than a portion with a gradation step, so the third threshold is greater than the first threshold for determining whether or not a gradation step exists. Also, a portion with a character or a pattern does not have a pixel value difference as great as a portion with an outline, so the third threshold is smaller than the second threshold.

[0032] If the second determination unit 12 determines that a character, pattern, or the like is present around the selected pixel of interest (Yes in step S12), the processes in steps S13 and S14 are not performed.

[0033] The processes in steps S11 and S12 may be performed in the order of steps S12 and S11. That is, when the second determination unit 12 performs a determination and the second determination unit 12 determines that no character or pattern exists around the selected pixel of interest, the first determination unit 11 may determine whether or not a contour exists around the selected pixel of interest.

[0034] When the first and second judgment units 11 and 12 judge that there is no outline around the selected pixel of interest and that there is no character or pattern (No in step S11 and No in step S12), the gradation step judgment unit 20 judges whether or not there is a gradation step (step S13). Specifically, when the first and second judgment units 11 and 12 judge that there is no pixel whose pixel value differs from the pixel value of the pixel of interest by a second threshold or more among the pixels adjacent to the pixel of interest and that there is no pixel whose pixel value differs from the pixel value of the pixel of interest by a third threshold or more among the pixels within a predetermined range, the gradation step judgment unit 20 judges whether or not the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than the first threshold. The judgment by the gradation step judgment unit 20 for pixels aligned horizontally will be described with reference to FIG. 3.

[0035] For example, the first pixel group is composed of pixels p0 to p6, and the second pixel group is composed of pixels p6 to p12. As shown in FIG. 3, the first pixel group and the second pixel group are adjacent to each other with the pixel of interest p6 as the boundary. The first pixel group may not include the pixel of interest p6, and the second pixel group may not include the pixel of interest p6. The first pixel group may include adjacent pixel groups including at least a pixel (here, pixel p5) adjacent to the pixel of interest p6, and the second pixel group may include adjacent pixel groups including at least a pixel (here, pixel p7) adjacent to the pixel of interest p6, and the number of pixels included in the first pixel group and the second pixel group is not limited. As described above, the first pixel group includes pixel p5 among the multiple pixels p0 to p12. The second pixel group includes pixel p7 among the multiple pixels p0 to p12. That is, the first pixel group may be made up of pixels p0 to p6, and the second pixel group may be made up of pixels p7 to p12. Alternatively, the first pixel group may be made up of pixels p0 to p5, and the second pixel group may be made up of pixels p6 to p12.

[0036] The gradation step determination unit 20 determines whether or not the difference between the average pixel value of the pixels p0 to p6 of the first pixel group (the average value of the pixel values ​​of the pixels p0 to p6) and the average pixel value of the pixels p6 to p12 of the second pixel group (the average value of the pixel values ​​of the pixels p6 to p12) is equal to or less than a first threshold. Specifically, the gradation step determination unit 20 determines whether or not the difference between the average pixel value of the pixels p0 to p6 of the first pixel group and the average pixel value of the pixels p6 to p12 of the second pixel group is equal to or less than the first threshold and equal to or greater than a fourth threshold. The fourth threshold is a threshold smaller than the first threshold and greater than 0. In other words, the gradation step determination unit 20 determines whether or not the difference is equal to or greater than the fourth threshold and equal to or less than the first threshold. The first threshold and the fourth threshold are thresholds for determining whether or not a gradation step exists in the pixels p0 to p12. A gradation step is a gradation step that occurs in a gradation region, and the presence or absence of a gradation step can be determined by comparing the average value of pixel values ​​that gradually change in the first pixel group with the average value of pixel values ​​that gradually change in the second pixel group. For example, since a portion with a gradation step does not have as much difference in pixel value as a portion with an outline or a portion with a character or pattern, the first threshold value is smaller than the reference value (specifically, the second threshold value and the third threshold value) for determining whether an outline, character, pattern, etc. exists.

[0037] If the gradation step determination unit 20 determines that no gradation step exists (No in step S13), that is, if the gradation step determination unit 20 determines that the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is not equal to or greater than the fourth threshold and equal to or less than the first threshold, the process in step S14 is not performed. For example, if the difference is greater than the first threshold, there is a possibility that a faint outline, character, pattern, or the like that could not be detected in step S11 or step S12 exists, so the process in step S14 is not performed. Also, for example, if the difference is less than the fourth threshold, there is no even a minute gradation step, so the process in step S14 is not performed.

[0038] If the gradation step determination unit 20 determines that a gradation step exists (Yes in step S13), that is, if the gradation step determination unit 20 determines that the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or greater than the fourth threshold and equal to or less than the first threshold, the correction unit 30 performs a correction process to correct the gradation step for a plurality of pixels including the pixel of interest (step S14). For example, the correction process of the correction unit 30 is a process to smooth the gradation step.

[0039] For example, the correction unit 30 may smooth out tone steps by performing low-pass filtering, for example, using a one-dimensional N-tap filter.

[0040] The correction process of the correction unit 30 does not have to be a process of smoothing out tone steps. For example, the correction unit 30 may correct tone steps by adding noise (for example, dithering).

[0041] Furthermore, even if the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is less than the fourth threshold (for example, 0), the correction section 30 may perform a correction process to correct tone steps.

[0042] Next, the image processing device 100 judges whether the horizontal processing is completed (step S15). For example, the image processing device 100 judges that the horizontal processing is completed when all pixels aligned in the horizontal direction are selected as pixels of interest and each process from step S11 is performed. When the horizontal processing is not completed (No in step S15), the image processing device 100 selects one pixel that has not yet been selected from the pixels aligned in the horizontal direction as a pixel of interest in step S10, and performs each process from step S11 on the pixel of interest. Note that the image processing device 100 may judge that the horizontal processing is completed when all pixels aligned in the horizontal direction in one row are selected as pixels of interest and each process is performed, or may judge that the horizontal processing is completed when all pixels aligned in the horizontal direction in multiple rows (for example, all rows) are selected as pixels of interest and each process is performed.

[0043] When the horizontal processing is completed (Yes in step S15), the image processing device 100 selects a pixel arranged in the vertical direction as a pixel of interest (step S20). For example, when the resolution is 1920×1080, the image processing device 100 selects one pixel as a pixel of interest from among 1080 pixels arranged in the vertical direction.

[0044] In steps S21 and S22, the judgment unit 10, using the first judgment unit 11 and the second judgment unit 12, judges whether or not there is a pixel within a specified range from the target pixel in a plurality of pixels (pixels lined up vertically) arranged on a straight line including the target pixel, whose pixel value difference from the pixel value of the target pixel is equal to or greater than a reference value.

[0045] The first determination unit 11 determines whether or not a contour exists around the selected pixel of interest (step S21). Specifically, the first determination unit 11 determines whether or not there exists a pixel whose pixel value differs from the pixel value of the pixel of interest by a second threshold value or more among pixels adjacent to the pixel of interest. The determination by the first determination unit 11 for pixels arranged vertically will be described with reference to FIG. 4.

[0046] FIG. 4 is a diagram showing an example of pixels arranged in the vertical direction.

[0047] 4 shows pixels q0 to q12 among a plurality of pixels (pixels arranged in the vertical direction) arranged on a straight line including the pixel of interest. For example, pixel q6 is the pixel of interest, and pixels q0 to q5 and pixels q7 to q12 are pixels within a predetermined range from the pixel of interest q6. The first determination unit 11 determines whether or not there is a pixel q5 or q7, which is adjacent to the pixel of interest q6, whose pixel value differs from the pixel value of the pixel of interest q6 by a second threshold value or more.

[0048] If the first determination unit 11 determines that a contour exists around the selected pixel of interest (Yes in step S21), the processes in steps S23 and S24 are not performed.

[0049] If the first judgment unit 11 judges that there is no contour around the selected pixel of interest (No in step S21), the second judgment unit 12 judges whether or not there is a character, pattern, or the like around the selected pixel of interest (step S22). Specifically, the second judgment unit 12 judges whether or not there is a pixel within a predetermined range whose pixel value differs from the pixel value of the pixel of interest by a third threshold value or more. The judgment by the second judgment unit 12 for pixels aligned vertically will be described with reference to FIG. 4.

[0050] The second determination unit 12 determines whether or not there is a pixel whose pixel value differs from the pixel value of the target pixel q6 by a third threshold value or more among the pixels q0 to q5 and pixels q7 to q12 within a predetermined range from the target pixel q6.

[0051] If the second determination unit 12 determines that a character, pattern, or the like is present around the selected pixel of interest (Yes in step S22), the processes in steps S23 and S24 are not performed.

[0052] The processes in steps S21 and S22 may be performed in the order of step S22 and step S21.

[0053] When the first and second judgment units 11 and 12 judge that there is no outline around the selected pixel of interest and that there is no character or pattern (No in step S21 and No in step S22), the gradation step judgment unit 20 judges whether or not there is a gradation step (step S23). Specifically, when the first and second judgment units 11 and 12 judge that there is no pixel whose pixel value differs from the pixel value of the pixel of interest by a second threshold or more among the pixels adjacent to the pixel of interest and that there is no pixel whose pixel value differs from the pixel value of the pixel of interest by a third threshold or more among the pixels within a predetermined range, the gradation step judgment unit 20 judges whether or not the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than the first threshold. The judgment by the gradation step judgment unit 20 for pixels aligned vertically will be described with reference to FIG. 4.

[0054] For example, the first pixel group is composed of pixels q0 to q6, and the second pixel group is composed of pixels q6 to q12. As shown in FIG. 4, the first pixel group and the second pixel group are adjacent to each other with the pixel of interest q6 as the boundary. The first pixel group may not include the pixel of interest q6, and the second pixel group may not include the pixel of interest q6. The first pixel group may include adjacent pixel groups including at least a pixel (here, pixel q5) adjacent to the pixel of interest q6, and the second pixel group may include adjacent pixel groups including at least a pixel (here, pixel q7) adjacent to the pixel of interest q6, and the number of pixels included in the first pixel group and the second pixel group is not limited. The gradation step determination unit 20 determines whether the difference between the average pixel value of the pixels q0 to q6 of the first pixel group and the average pixel value of the pixels q6 to q12 of the second pixel group is equal to or less than a first threshold value. Specifically, the gradation step determination unit 20 determines whether the difference between the average pixel value of pixels q0 to q6 in the first pixel group and the average pixel value of pixels q6 to q12 in the second pixel group is less than or equal to a first threshold value and greater than or equal to a fourth threshold value.

[0055] If the gradation step determination unit 20 determines that no gradation step exists (No in step S23), that is, if the gradation step determination unit 20 determines that the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is not greater than the fourth threshold and less than the first threshold, the processing in step S24 is not performed.

[0056] If the gradation step determination unit 20 determines that a gradation step exists (Yes in step S23), that is, if the gradation step determination unit 20 determines that the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is greater than or equal to the fourth threshold and less than the first threshold, the correction unit 30 performs a correction process to correct the gradation step (step S24).

[0057] Next, the image processing device 100 judges whether the vertical processing is completed (step S25). For example, the image processing device 100 judges that the vertical processing is completed when all pixels aligned in the vertical direction are selected as pixels of interest and each process from step S21 is performed. If the vertical processing is not completed (No in step S25), the image processing device 100 selects one pixel that has not yet been selected from the pixels aligned in the vertical direction as a pixel of interest in step S20, and performs each process from step S21 on the pixel of interest. Note that the image processing device 100 may judge that the vertical processing is completed when all pixels aligned in the vertical direction in one column are selected as pixels of interest and each process is performed, or may judge that the vertical processing is completed when all pixels aligned in the vertical direction in multiple columns (for example, all columns) are selected as pixels of interest and each process is performed.

[0058] Although the memory 40 is, for example, a line memory that stores pixel values ​​of pixels for each horizontal or vertical line of a video signal input to the image processing device 100, the memory 40 may be a frame memory and may store frames. In this case, the multiple pixels arranged on a straight line including the pixel of interest may be pixels arranged in a diagonal direction (for example, a direction that forms an angle of 45 degrees with the horizontal or vertical direction) as shown in Fig. 5.

[0059] FIG. 5 is a diagram showing an example of pixels arranged in a diagonal direction.

[0060] In this case, the first determination unit 11 determines whether or not there is a pixel whose pixel value differs from the pixel value of the pixel of interest r6 by a second threshold value or more among pixels r5 and r7 adjacent to the pixel of interest r6. The second determination unit 12 determines whether or not there is a pixel whose pixel value differs from the pixel value of the pixel of interest r6 by a third threshold value or more among pixels r0-r5 and pixels r7-r12 within a predetermined range from the pixel of interest r6. The gradation step determination unit 20 determines whether or not the difference between the average pixel value of the pixels r0-r6 of the first pixel group and the average pixel value of the pixels r6-r12 of the second pixel group is equal to or less than a first threshold value.

[0061] Although an example has been described in which the judgment unit 10 has both the first judgment unit 11 and the second judgment unit 12, the judgment unit 10 may have only one of them. When the judgment unit 10 has only the first judgment unit 11, it may judge whether or not a contour exists, and when no contour exists, it may judge whether or not a gradation step exists. Alternatively, when the judgment unit 10 has only the second judgment unit 12, it may judge whether or not a character or a pattern exists, and when no character or a pattern exists, it may judge whether or not a gradation step exists.

[0062] In addition, the pixel range used to determine whether or not a contour exists, the pixel range used to determine whether or not a character or pattern exists, and the ranges of the first pixel group and the second pixel group used to determine whether or not a gradation step exists may be the same or different.

[0063] In addition, the correction unit 30 may perform the correction process only on the pixel of interest, or may perform the correction process on the pixels used to determine whether or not a contour exists, or the pixels used to determine whether or not a character or a pattern exists.

[0064] As described above, the image processing device 100 includes a determination unit 10 that determines whether or not there is a pixel among a plurality of pixels arranged on a straight line including a target pixel, the pixel having a pixel value that differs from the pixel value of the target pixel by a reference value or more, a gradation step determination unit 20 that determines, when it is determined that there is no pixel having a pixel value that differs from the pixel value of the target pixel by a reference value or more, for a first pixel group and a second pixel group adjacent to each other across the target pixel, the plurality of pixels arranged on a straight line, whether or not the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than a first threshold value, and a correction unit 30 that performs a correction process to correct a gradation step when it is determined that the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than the first threshold value.

[0065] The reference value is a threshold value for determining whether or not a contour, a character, or a pattern exists within a predetermined range from the pixel of interest. According to the present disclosure, before determining whether or not the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than the first threshold value (i.e., determining whether or not a gradation step exists), a determination is made as to whether or not a pixel exists within a predetermined range from the pixel of interest, the pixel value of which is different from the pixel value of the pixel of interest by a reference value or more (i.e., determining whether or not a contour, a character, a pattern, or the like exists). If a contour, a character, a pattern, or the like does not exist, a determination is made as to whether or not a gradation step exists, and if a gradation step exists, a correction process is performed to correct the gradation step. If a contour, a character, a pattern, or the like exists, a determination is not made as to whether or not a gradation step exists, and a correction process is not performed to correct the gradation step, so that a decrease in the sharpness of a portion that is not a gradation step (for example, a contour, a character, a pattern, or the like of an image) can be suppressed. Therefore, a decrease in the sharpness of a portion that is not a gradation step can be suppressed while reducing the gradation step.

[0066] For example, the judgment unit 10 may have a first judgment unit 11, and the pixels within a predetermined range from the target pixel may include pixels adjacent to the target pixel in a plurality of pixels arranged in a straight line, and the first judgment unit 11 may judge whether or not there is a pixel among the pixels adjacent to the target pixel whose pixel value differs from the pixel value of the target pixel by a reference value or more.

[0067] The reference value is, for example, a threshold value for determining whether or not a contour exists. According to this aspect, before determining whether or not the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than the first threshold value (i.e., determining whether or not a tone step exists), a determination is made as to whether or not a pixel adjacent to the pixel of interest has a pixel value whose difference from the pixel value of the pixel of interest is equal to or greater than a reference value (i.e., determining whether or not a contour exists). If a contour does not exist, a determination is made as to whether or not a tone step exists, and if a tone step exists, a correction process is performed to correct the tone step. If a contour exists, a determination is not made as to whether or not a tone step exists, and a correction process is not performed to correct the tone step, so that a decrease in the sharpness of a portion that is not a tone step (e.g., a contour) can be suppressed.

[0068] For example, the determination unit 10 may have a first determination unit 11 and a second determination unit 12, and the pixels within the predetermined range from the pixel of interest may include pixels adjacent to the pixel of interest in a plurality of pixels arranged on a line, and the reference value may include a second threshold value and a third threshold value. The first determination unit 11 may determine whether or not there is a pixel having a pixel value that is different from the pixel value of the pixel of interest by a second threshold value or more among the pixels adjacent to the pixel of interest, and the second determination unit 12 may determine whether or not there is a pixel having a pixel value that is different from the pixel value of the pixel of interest by a third threshold value or more among the pixels within the predetermined range. The gradation step determination unit 20 may determine whether or not the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than the first threshold value when it is determined that there is no pixel having a pixel value that is different from the pixel value of the pixel of interest by a second threshold value or more among the pixels adjacent to the pixel of interest and that there is no pixel having a pixel value that is different from the pixel value of the pixel of interest by a third threshold value or more among the pixels within the predetermined range.

[0069] The second threshold is a threshold for determining whether or not a pixel value difference of more than a gradation step occurs between the pixel of interest and an adjacent pixel (e.g., a contour exists). The third threshold is a threshold for determining whether or not a pixel value difference of more than a gradation step occurs within a predetermined range from the pixel of interest (e.g., a character or a pattern exists). For example, a portion with a contour, character, or pattern will have a larger pixel value difference than a portion with a gradation step, so the second and third thresholds are larger than the first threshold. Also, a portion with a character or a pattern will not have as large a pixel value difference as a portion with a contour, so the third threshold is smaller than the second threshold. According to this aspect, before determining whether the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than a first threshold value (i.e., determining whether a gradation step exists), a determination is made as to whether a pixel adjacent to the pixel of interest has a pixel value whose difference from the pixel value of the pixel of interest is equal to or more than a second threshold value (i.e., determining whether a contour exists), and a determination is made as to whether a pixel within a predetermined range from the pixel of interest has a pixel value whose difference from the pixel value of the pixel of interest is equal to or more than a third threshold value (i.e., determining whether a character or a pattern exists). If there is no contour and no character or pattern, a determination is made as to whether a gradation step exists, and if there is a gradation step, a correction process is performed to correct the gradation step. If there is a contour, character, pattern, or the like, a determination as to whether a gradation step exists is not performed, and a correction process is not performed to correct the gradation step, so that a decrease in the sharpness of a portion that does not have a gradation step (for example, a contour, character, pattern, etc.) can be suppressed.

[0070] For example, the gradation step determination unit 20 may determine whether the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is less than a first threshold value and greater than a fourth threshold value that is smaller than the first threshold value and greater than 0.

[0071] According to this, when the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or greater than 0 and less than the fourth threshold, it is possible to avoid performing correction processing for correcting tone steps.

[0072] For example, the image processing device 100 performs a determination by the determination unit 10, a determination by the tone step determination unit 20, and a correction process by the correction unit 30, with each of the pixels (plurality of horizontal input pixels) arranged in the horizontal direction included in the video signal input to the image processing device 100 being a pixel of interest. Furthermore, the image processing device 100 may perform a determination by the determination unit 10, a determination by the tone step determination unit 20, and a correction process by the correction unit 30, with each of the pixels (plurality of vertical input pixels) arranged in the vertical direction included in the video signal input to the image processing device 100 being a pixel of interest.

[0073] According to this, horizontal and vertical processing can be performed using several line memories, without using a frame memory, etc. This makes it possible to reduce the delay in processing time compared to processing using a frame memory, and also makes it possible to reduce costs by not using a frame memory.

[0074] For example, the correction process of the correction unit 30 may be a process for smoothing out tone steps.

[0075] For example, as a correction process for correcting tone steps, there are a method of making tone steps less noticeable by adding noise, and a method of making tone steps less noticeable by smoothing processing. However, adding noise has a problem of image quality degradation due to noise. Therefore, by performing smoothing processing as a correction process for correcting tone steps, it is possible to suppress image quality degradation due to noise.

[0076] (Other embodiments) As described above, the embodiments have been described as examples of the technology disclosed in this application. However, the technology in this disclosure is not limited to these, and can be applied to embodiments in which modifications, substitutions, additions, omissions, etc. are appropriately made. In addition, it is also possible to combine the components described in the above embodiments to create new embodiments.

[0077] For example, in the above embodiment, the video signal is an RGB signal, but the video signal may be a YUV signal, a YPbPr signal, or an HSV signal.

[0078] For example, the present disclosure can be realized not only as the image processing device 100 but also as an image processing method including steps (processing) performed by the components that make up the image processing device 100.

[0079] FIG. 6 is a flowchart showing an example of an image processing method according to another embodiment.

[0080] Specifically, as shown in FIG. 6, the image processing method includes the steps of: determining whether or not there are any pixels among a plurality of pixels arranged on a straight line including a pixel of interest, within a predetermined range from the pixel of interest, whose pixel value differs from that of the pixel of interest by a reference value or more (step S1); if it is determined that there are no pixels whose pixel value differs from that of the pixel of interest by a reference value or more, determining whether or not, for a first pixel group and a second pixel group adjacent to each other across the pixel of interest, whose pixel value differs from that of the pixel of interest by a reference value or more, in the plurality of pixels arranged on a straight line, between the first pixel group and the second pixel group, whose boundary is the pixel of interest, the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than a first threshold value (step S2); if it is determined that the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or less than the first threshold value, performing a correction process to correct tone steps (step S3).

[0081] For example, the image processing method may be executed by a computer (computer system). The present disclosure may be realized as a program for causing a computer to execute steps included in the image processing method. Furthermore, the present disclosure may be realized as a non-transitory computer-readable recording medium, such as a CD-ROM, on which the program is recorded.

[0082] For example, when the present disclosure is realized by a program (software), each step is executed by executing the program using hardware resources such as a computer's CPU, memory, input / output circuitry, etc. In other words, each step is executed by the CPU acquiring data from memory or input / output circuitry, etc., performing calculations, and outputting the results of calculations to memory or input / output circuitry, etc.

[0083] Furthermore, the components included in the image processing device 100 according to the above embodiment may be realized as an LSI (Large Scale Integration) integrated circuit (IC: Integrated Circuit).

[0084] In addition, the integrated circuit is not limited to an LSI, and may be realized by a dedicated circuit or a general-purpose processor. A programmable FPGA or a reconfigurable processor in which the connections and settings of circuit cells within an LSI can be reconfigured may also be used.

[0085] Furthermore, if an integrated circuit technology that can replace LSI emerges due to advances in semiconductor technology or a different derivative technology, the components included in the image processing device 100 may naturally be integrated into an integrated circuit using that technology.

[0086] As described above, the embodiments have been described as examples of the technology in the present disclosure. For this purpose, the attached drawings and detailed description have been provided.

[0087] Therefore, the components shown in the attached drawings and detailed description may include not only essential components for solving the problem, but also non-essential components for solving the problem. Therefore, the fact that such non-essential components are shown in the attached drawings or detailed description should not be interpreted as indicating that such non-essential components are essential.

[0088] Furthermore, since the above-described embodiments are intended to illustrate the technology in the present disclosure, various modifications, substitutions, additions, omissions, and the like can be made within the scope of the claims or their equivalents. [Industrial Applicability]

[0089] The present disclosure can be applied to an image processing device or the like that reduces gradation steps that occur in gradation areas in a displayed image due to roughness in quantization of a video signal. [Explanation of symbols]

[0090] 10 Judgment section 11 1st judgment section 12 Second Judgment Section 20 Gradation level difference determination section 30 Correction section 40 Memory 100 Image processing device

Claims

1. a determination unit that determines whether or not there is a pixel having a pixel value whose difference from the pixel value of the pixel of interest is equal to or greater than a reference value, among a plurality of pixels that are arranged in a line, including a pixel of interest, a first adjacent pixel adjacent to the pixel of interest, and a second adjacent pixel adjacent to the pixel of interest and located opposite the first adjacent pixel; a gradation step determination unit that, when the determination unit determines that there is no pixel having a pixel value whose difference from the pixel value of the target pixel is equal to or greater than the reference value, determines whether or not a difference between an average pixel value of a first pixel group including the first adjacent pixel among the plurality of pixels and an average pixel value of a second pixel group including the second adjacent pixel among the plurality of pixels is equal to or less than a first threshold value; a correction unit that corrects a gradation step of at least one pixel among the plurality of pixels when the gradation step determination unit determines that a difference between an average pixel value of the first pixel group and an average pixel value of the second pixel group is equal to or smaller than the first threshold value, Image processing device.

2. The determination unit includes a first determination unit, the first determination unit determines whether or not there is a pixel among the first adjacent pixel and the second adjacent pixel, the pixel value of which has a difference from the pixel value of the target pixel that is equal to or greater than the reference value; when the first determination unit determines that there is no pixel having a pixel value whose difference from the pixel value of the target pixel is equal to or greater than the reference value, the gradation step determination unit determines whether or not a difference between an average pixel value of the first pixel group and an average pixel value of the second pixel group is equal to or less than a first threshold value; The image processing device according to claim 1 .

3. The determination unit includes a first determination unit and a second determination unit, the first determination unit determines whether or not there is a pixel among the first adjacent pixel and the second adjacent pixel, the pixel value of which differs from the pixel value of the target pixel by a second threshold value or more; the second determination unit determines whether or not there is a pixel among the plurality of pixels, the pixel value of which differs from the pixel value of the pixel of interest by a third threshold value or more; when the first determination unit determines that there is no pixel having a pixel value whose difference from the pixel value of the target pixel is equal to or greater than the second threshold value and the second determination unit determines that there is no pixel having a pixel value whose difference from the pixel value of the target pixel is equal to or greater than the third threshold value, the gradation step determination unit determines whether or not a difference between an average pixel value of the first pixel group and an average pixel value of the second pixel group is equal to or less than the first threshold value. The image processing device according to claim 1 .

4. The second threshold value is greater than the reference value, The third threshold value is equal to the reference value. The image processing device according to claim 3 .

5. the gradation step determination unit determines whether a difference between an average pixel value of the first pixel group and an average pixel value of the second pixel group is equal to or smaller than the first threshold and equal to or larger than a fourth threshold that is smaller than the first threshold and larger than 0; when the gradation step determination unit determines that a difference between an average value of the pixel values ​​of the first pixel group and an average value of the pixel values ​​of the second pixel group is equal to or smaller than the first threshold value and equal to or larger than the fourth threshold value, the correction unit corrects a gradation step of the at least one pixel among the plurality of pixels. The image processing device according to any one of claims 1 to 4.

6. The image processing device includes: a determination unit that determines whether or not a pixel is a pixel of interest, the determination unit that determines whether or not a pixel is a pixel of interest, and the correction unit that corrects the pixel of interest is corrected, the determination unit that determines whether or not a pixel is a pixel of interest, and the correction unit that corrects the pixel of interest is corrected, the image processing device being input to the image processing device; a determination unit determines whether or not a plurality of vertical input pixels arranged in a vertical direction included in the video signal are included in the video signal, and the determination unit determines whether or not a plurality of vertical input pixels arranged in a vertical direction are included in the video signal, and the determination unit determines whether or not a plurality of vertical input pixels are included in the video signal, ... The image processing device according to any one of claims 1 to 5.

7. The correction unit smoothes the gradation step to correct the gradation step. The image processing device according to any one of claims 1 to 6.

8. The first threshold value is smaller than the reference value. The image processing device according to any one of claims 1 to 7.

9. the first pixel group includes the pixel of interest and does not include the second adjacent pixel; the second pixel group includes the pixel of interest and does not include the first adjacent pixel; The image processing device according to any one of claims 1 to 8.

10. the first pixel group does not include the pixel of interest and the second adjacent pixel, the second pixel group does not include the pixel of interest and the first adjacent pixel; The image processing device according to any one of claims 1 to 8.

11. the first pixel group includes the pixel of interest and does not include the second adjacent pixel; the second pixel group does not include the pixel of interest and the first adjacent pixel; The image processing device according to any one of claims 1 to 8.

12. the first pixel group does not include the pixel of interest and the second adjacent pixel, the second pixel group includes the pixel of interest and does not include the first adjacent pixel; The image processing device according to any one of claims 1 to 8.

13. determining whether or not there is a pixel having a pixel value whose difference from the pixel value of the pixel of interest is equal to or greater than a reference value among a plurality of pixels arranged in a line including a pixel of interest, a first adjacent pixel adjacent to the pixel of interest, and a second adjacent pixel adjacent to the pixel of interest and located opposite to the first adjacent pixel; when it is determined that there is no pixel having a pixel value whose difference from the pixel value of the target pixel is equal to or greater than the reference value, it is determined whether or not a difference between an average value of pixel values ​​of a first pixel group including the first adjacent pixel among the plurality of pixels and an average value of pixel values ​​of a second pixel group including the second adjacent pixel among the plurality of pixels is equal to or less than a first threshold value; correcting a gradation step of at least one pixel among the plurality of pixels when it is determined that the difference between the average pixel value of the first pixel group and the average pixel value of the second pixel group is equal to or smaller than the first threshold value; Image processing methods.

14. A program for causing a computer to execute the image processing method according to claim 13.

Images