JP2011118000A - Image processing apparatus and image processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve image quality of a reduced image by suppressing image quality deterioration caused when an image is reduced to the utmost. <P>SOLUTION: The image processing apparatus is constituted such that, when a plurality of object pixels extracted from an original image being an object to be reduced containing pixels including a prescribed number of subpixels are made to correspond to one reduced pixel corresponding to the plurality of object pixels on the reduced image being a destination of reduction, thereby generating the reduced image from the original image, pixel groups which continue in the same direction as an arraying direction of the subpixels and include at least the plurality of object pixels are selected from the original image, luminance data as many as the subpixels included in the one reduced pixel are generated on the basis of a relative position between the pixels included in the pixel group and the luminance data of the pixels included in the pixel group, and the generated luminance data are set as the luminance data for the subpixels in the reduced pixel, and then the reduced image to which the luminance data are set is displayed on a prescribed display part. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image processing apparatus and an image processing method, and more particularly to an image processing apparatus and an image processing method that can improve the image quality of a reduced image by suppressing image quality degradation that occurs when an image is reduced.

  Conventionally, as an image reduction method for generating a reduced image from an original image, a method is known in which a number of pixels (pixels) corresponding to a reduction rate are thinned out from the original image and a reduced image is generated using the remaining pixels.

  When a reduced image is generated by thinning out pixels from the original image in this way, a line that was displayed as a smooth diagonal line in the original image may be displayed as a jagged diagonal line in the reduced image by thinning out the pixel. .

  Therefore, in recent years, image processing has been used in which an image is reduced by generating image data for one pixel of a reduced image from image data constituting a plurality of pixels in the original image, instead of thinning out pixels from the original image. It is getting to be.

  For example, Patent Document 1 discloses a technique for generating image data for one pixel of a reduced image from image data for two adjacent pixels in an original image and reducing the image.

JP 2007-93832 A

  However, in the conventional general image processing, when each RGB value in one pixel of the reduced image is determined from two adjacent target pixels selected from the original image as the reduction target, based on the luminance data of each target pixel, for example, One type of luminance data is generated by calculating the average value of the luminance of each target pixel.

  In the conventional image processing, each RGB value in one pixel of the reduced image is determined by substituting the calculated one type of luminance data into a predetermined RGB matrix conversion formula.

  For this reason, in the conventional image processing, if there is a difference in the brightness of each target pixel selected from the original image, the difference between the brightness is smoothed by the reduction of the image. The difference in luminance of the pixels cannot be reproduced, and there is a possibility that the image quality is deteriorated.

  For this reason, how to realize an image processing apparatus and an image processing method capable of improving the image quality of a reduced image by minimizing image quality degradation that occurs when the image is reduced is a major issue.

  The present invention has been made to solve the above-described problems caused by the prior art, and is an image processing apparatus capable of improving the image quality of a reduced image by minimizing image quality degradation caused when the image is reduced. It is another object of the present invention to provide an image processing method.

  In order to solve the above-described problems and achieve the object, the present invention is an image processing apparatus for processing an image including pixels including a predetermined number of subpixels, and a plurality of images extracted from an original image to be reduced A reduced image generating means for generating the reduced image from the original image by associating the target pixel with one reduced pixel corresponding to the plurality of target pixels on the reduced image to be reduced, and the subpixel A pixel group that is continuous in the same direction as the array direction and includes at least the plurality of target pixels is selected from the original image, and a relative position between pixels included in the pixel group and each pixel included in the pixel group are selected. Generation means for generating the same number of luminance data as the predetermined number, and each luminance data generated by the generation means is converted into luminance data of each sub-pixel in the reduced pixel. An image processing apparatus comprising: brightness data setting means for setting as a data; and display control means for displaying a reduced image in which the brightness data is set by the brightness data setting means on a predetermined display unit, and an image processing method using the same It was decided to provide.

  According to the present invention, based on the luminance data of a plurality of target pixels selected from the original image as the reduction target, based on the relative position between the pixels and the luminance data of each pixel included in the pixel group, Create the same number of luminance data as the number of pixels, and set the generated luminance data as the luminance data of each sub-pixel in the reduced pixel, so that the difference in luminance of multiple target pixels extracted from the original image to be reduced Can be reproduced by the difference in luminance of each sub-pixel in the reduced pixel. Therefore, the image quality of the reduced image can be improved by minimizing image quality degradation that occurs when the image is reduced.

FIG. 1 is a diagram showing an outline of a conventional image processing method. FIG. 2 is a diagram showing an outline of the image processing method according to the present invention. FIG. 3 is a block diagram illustrating the configuration of the in-vehicle device according to the present embodiment. FIG. 4 is a block diagram illustrating the configuration of the display device according to the present embodiment. FIG. 5 is a block diagram illustrating the configuration of the pixel control unit according to the present embodiment. FIG. 6 is a diagram showing a first generation procedure of luminance data by the luminance data generation unit in the present embodiment. FIG. 7 is a diagram showing a second generation procedure of luminance data by the luminance data generation unit in the present embodiment. FIG. 8 is a diagram showing a cause of coloring that occurs in the edge region and the vertical line, and a method for reducing coloring. FIG. 9 is a diagram illustrating a cause of coloring and a method for reducing coloring depending on the arrangement order of sub-pixels selected as reduced pixels. FIG. 10 is a flowchart illustrating a processing procedure of the preprocessing unit included in the subpixel control unit. FIG. 11 is a flowchart illustrating a processing procedure of a post-processing unit included in the sub-pixel control unit.

  Exemplary embodiments of an image processing apparatus and an image processing method according to the present invention will be described below in detail with reference to the accompanying drawings.

  First, prior to detailed description of the embodiments, an outline of an image processing method according to the present invention will be described in comparison with a conventional image processing method. FIG. 1 is a diagram showing an overview of a conventional image processing method, and FIG. 2 is a diagram showing an overview of an image processing method according to the present invention.

  In the following description, an image processing procedure when an original image of VGA (800 × 480) size is reduced and displayed on a display of EGA (400 × 240) size will be described as an example.

  A display device that displays an original image or a reduced image is configured by arranging three subpixels corresponding to each of the three primary colors R (red), G (green), and B (blue) in the order of RGB 1 It is assumed that a plurality of pixels (pixels) are arranged in a matrix.

  Hereinafter, the arrangement direction in which the three sub-pixels constituting one pixel are arranged will be described as a horizontal direction, and the direction orthogonal to the horizontal direction will be described as a vertical direction.

  Conventionally, when a VGA (800 × 480) size original image is reduced and displayed on an EGA (400 × 240) size display, the original image is reduced by a factor of 1/2 in the vertical and horizontal directions. Processing is in progress.

  When the original image is reduced by a factor of 1/2 in the horizontal direction, in the conventional image processing method, as shown in FIG. 1A, two target pixels P0 adjacent in the horizontal direction as pixels to be reduced, P1 is selected from the original image. Here, it is assumed that the luminance data indicating the luminance of the target pixel P0 is Y0 and the luminance data indicating the luminance of the target pixel P1 is Y1.

  Subsequently, in the conventional image processing method, one type of luminance data Y01 is generated, for example, by calculating an average value of luminances of the target pixels P0 and P1 based on the luminance data Y0 and Y1 of the target pixels P0 and P1. Was.

  Thereafter, in the conventional image processing method, the calculated one type of luminance data Y01 is set as luminance data of one pixel of the reduced image (hereinafter referred to as “reduced pixel P01”).

  Specifically, each RGB value in the reduced pixel P01 is substituted by substituting one type of luminance data Y01 calculated from the luminance data Y0 and Y1 of the original image into the RGB matrix conversion equation shown in FIG. Had decided.

  For this reason, in the conventional image processing procedure, even if there is a difference between the luminances of the two target pixels P0 and P1, the luminances of the sub-pixels constituting the reduced pixel P01 are all the same.

  Therefore, in the conventional image processing method, even if there is a difference in luminance between the two pixels P0 and P1 before reduction, such difference is not reflected in the reduction pixel P01. Therefore, there is a risk of degrading the image quality of the reduced image.

  Therefore, in the present invention, as shown in FIG. 2A, the luminance of the target pixels P0 and P1 is based on the luminance data Y0 and Y1 of a plurality of (here two) target pixels P0 and P1 selected from the original image. According to the difference, three types of luminance data Yr, Yg, and Yr having different luminances are generated. Then, the generated luminance data (Yr, Yg, and Yr) are set as the luminance data of the three sub-pixels constituting the reduced pixel P01.

  Specifically, in the present invention, a plurality of pixels including at least the target pixels P0 and P1 are selected from the plurality of pixels arranged on the same horizontal line as the target pixels P0 and P1, and the selected plurality of pixels is selected. The luminance values of three virtual pixels (pixels indicated by broken lines in FIG. 2A) arranged in the horizontal direction are determined based on each array position and each luminance data.

  Here, the virtual pixel located in the middle of the three virtual pixels (hereinafter referred to as “middle pixel”) is the midpoint between the target pixels P0 and P1 at the center of the pixel (see “X0” in the figure). Assume that Further, it is assumed that the other two virtual pixels are equidistant from the midpoint between the target pixels P0 and P1.

  In the present invention, luminance data of each virtual pixel is determined based on a virtual positional relationship between the target pixel (for example, P0 and P1) and each virtual pixel.

  In FIG. 2A, three virtual pixels are shown for ease of explanation. However, in actual image processing, three virtual pixels are not generated, and a predetermined number described in detail later is used. Luminance data corresponding to each of the three virtual pixels is calculated by interpolation processing.

  Subsequently, in the present invention, luminance data Yg indicating the luminance of the middle pixel, luminance data Yr of the virtual pixel closer to the target pixel P0 than the middle pixel, luminance data Yb of the virtual pixel closer to the target pixel P1 than the middle pixel, Calculate each.

  In the present invention, as shown in FIG. 2B, each of the three types of luminance data Yr, Yg, and Yr calculated above is substituted into the RGB matrix conversion formula, so that each pixel in the reduced pixel P01 Determine RGB values.

  Therefore, in the present invention, the luminance of the target pixel P0 is strongly reflected in the luminance of the subpixel corresponding to R in the reduced pixel P01, and the luminance of the target pixels P0 and P1 is reflected in the luminance of the subpixel corresponding to G. The luminance of the target pixel P1 is strongly reflected in the luminance of the sub-pixel corresponding to B.

  As described above, in the present invention, the luminances of the three sub-pixels constituting the reduced pixel P01 can be individually adjusted according to the luminance difference between the target pixels P0 and P1. Therefore, the difference in luminance between the target pixels P0 and P1 can be reproduced by the difference in luminance between the sub-pixels constituting the reduced pixel P01.

  As a result, according to the present invention, when an original image that includes a subtle gradation is reduced, a reduced image that reproduces the subtle gradation of the original image with higher reproducibility than the conventional image processing procedure is generated. be able to. Therefore, it is possible to improve the image quality of the reduced image by suppressing the deterioration of the image quality due to the image reduction.

  Below, the Example about the image processing apparatus to which the image processing method demonstrated using FIG. 2 is applied is described in detail. In the following embodiments, a display device mounted on an in-vehicle device in which a plurality of functions such as a navigation function, a TV function, or a DVD (Digital Versatile Disc) function are integrated will be described as an example of an image processing apparatus. . However, the image processing apparatus according to the present invention can be applied to various apparatuses that display images.

  In the embodiment described below, a case where an original image of VGA (800 × 480) size is reduced by half and displayed on a display of EGA (400 × 240) size will be described. Is not limited to this.

  FIG. 3 is a block diagram illustrating the configuration of the in-vehicle device according to the present embodiment. In the figure, only components necessary for explaining the characteristics of the in-vehicle device 1 are shown, and descriptions of general components are omitted.

  As shown in the figure, the in-vehicle device 1 according to the present embodiment includes a navigation engine 11, a TV (Television) tuner 12, a DVD deck 13, a rear camera 14, an audio microcomputer 15, a drawing unit 16, A video switching unit 17 and a display device 18 are provided.

  The navigation engine 11 is a device that manages various car navigation functions such as vehicle guidance and route search. For example, the navigation engine 11 generates a navigation image using map information, position information of the host vehicle, VICS (Vehicle Information and Communication System) information, and the like, and outputs image data of the generated navigation image to the drawing unit 16. The TV tuner 12 receives an analog TV broadcast wave or a digital TV broadcast wave from the antenna, and outputs image data included in the received broadcast wave to the video switching unit 17.

  The DVD deck 13 is a DVD playback device and outputs image data read from the DVD to the video switching unit 17. The rear camera 14 is a camera installed behind the vehicle, and outputs image data obtained by imaging the rear of the vehicle to the video switching unit 17. The audio microcomputer 15 is a device that outputs a guide voice according to an instruction from the navigation engine 11 and a voice input from the TV tuner 12 or the DVD deck 13. In particular, when the change of the volume setting value is received, the audio microcomputer 15 generates an image indicating the current volume setting value (hereinafter referred to as “volume display image”) and outputs the image to the display device 18.

  The drawing unit 16 is image data of a composite image (hereinafter referred to as “combined navigation image”) obtained by combining a navigation image input from the navigation engine 11 with a GUI (Graphical User Interface) image such as a menu screen or a button. Is a drawing device that outputs to the display device 18. The video switching unit 17 selects one image data from the image data input from the TV tuner 12, the DVD deck 13, or the rear camera 14 according to an instruction from the display device 18, and displays the selected image data. It is a device that outputs to the device 18.

  The display device 18 is a device that displays the image data of the composite navigation image input from the drawing unit 16, the image data input from the video switching unit 17, and the image data of the volume display image input from the audio microcomputer 15.

  Next, the configuration of the display device 18 shown in FIG. 3 will be described in detail with reference to FIG. FIG. 4 is a block diagram illustrating the configuration of the display device 18 according to the present embodiment. In the figure, only components necessary for explaining the characteristics of the display device 18 are shown, and descriptions of general components are omitted.

  As shown in the figure, the display device 18 includes a power source 81, a TFT (Thin Film Transistor) panel 82, a microcomputer processing unit 83, an LVDS (Low Voltage Differential Signaling) receiver 84, a reduced image generation unit 85, A gradation processing unit 86, a pixel control unit 87, a timing control unit 88, and a memory 89 are provided. The power supply 81 is a device that supplies power to the TFT panel 82. The TFT panel 82 is a display device that displays various images.

  The microcomputer processing unit 83 is a control unit that controls the entire display device 18. The microcomputer processing unit 83 also selects from among image data input from the drawing unit 16, image data input from the video switching unit 17, and image data input from the audio microcomputer 15 in accordance with a user operation or the like. One image data is selected and input to the LVDS receiver 84.

  Further, the microcomputer processing unit 83 instructs the video switching unit 17 to switch the video in accordance with an operation from the user. As the microcomputer processing unit 83, for example, a CPU (Central Processing Unit), an integrated circuit equipped with a CPU and a memory, or the like can be used.

  The LVDS receiver 84 is an image interface that can transmit a large amount of image data at high speed. When image data is input, the LVDS receiver 84 outputs the input image data to the reduced image generation unit 85.

  The reduced image generation unit 85 reduces the size of the image data (original image) to the display size of the TFT panel 82 when the size of the image data input from the LVDS receiver 84 is larger than the display size of the TFT panel 82. A processing unit that performs processing.

  For example, when reducing the VGA (800 × 480) size original image to the EGA (400 × 240) size, the reduced image generation unit 85 first performs a reduction process of halving the original image in the vertical direction, Thereafter, a reduction process is performed in which the original image that has been halved in the vertical direction is halved in the horizontal direction. Although not shown here, the reduced image generation unit 85 is connected to the pixel control unit 87.

  When the reduced image generating unit 85 according to the present embodiment reduces the original image by a factor of 1/2 in the horizontal direction, the reduced image generation unit 85 determines the reduced pixel P01 based on pixel control data input from the pixel control unit 87 described later. A reduced image in which image quality deterioration is suppressed is generated by individually adjusting the luminances of the three sub-pixels constituting the image, and the generated reduced image is stored in the memory 89.

  The gradation processing unit 86 is a processing unit that extracts the reduced image stored in the memory 89 and performs gradation conversion on the extracted reduced image. Specifically, the gradation processing unit 86 converts the gradation information of the image data from 8 bits to 6 bits.

  The pixel control unit 87 is a processing unit that performs pixel control on the reduced image. For example, the pixel control unit 87 determines the distribution of R, G, and B for each pixel of the reduced image.

  In addition, when displaying the reduced image, the pixel control unit 87 selects the combination of three subpixels to be used as the reduced pixel P01 from among RGB, GBR, and BRG, so that the reduced image appears in the horizontal direction. Sub-pixel rendering is performed to triple the resolution of.

  In particular, the pixel control unit 87 in the present embodiment performs pixel control that suppresses deterioration of the image quality of the reduced image by individually adjusting the luminances of the three sub-pixels constituting the reduced pixel P01 generated from the original image. Do. A specific configuration and operation of the pixel control unit 87 will be described later with reference to FIGS.

  The timing control unit 88 is a processing unit that determines the frame frequency of the reduced image generated by the reduced image generation unit 85. Then, the timing control unit 88 sequentially displays each reduced image on the TFT panel 82 using the determined frame frequency. In this embodiment, the timing control unit 88 functions as a display control unit that displays a reduced image whose luminance is adjusted in units of subpixels on the TFT panel 82 as a predetermined display unit.

  The memory 89 is a storage device that stores the reduced image generated by the reduced image generation unit 85. As the memory 89, for example, a volatile memory element such as SDRAM (Synchronous Dynamic Random Access Memory) can be used.

  Next, the configuration of the pixel control unit 87 according to the present embodiment will be specifically described with reference to FIG. FIG. 5 is a block diagram illustrating the configuration of the pixel control unit 87 according to the present embodiment. In the figure, only components necessary for explaining the features of the pixel control unit 87 are shown, and descriptions of general components are omitted.

  As shown in FIG. 5, the pixel control unit 87 includes a preprocessing unit 71 and a postprocessing unit 72. The pre-processing unit 71 is a processing unit that performs pixel control that individually adjusts the luminance of the three sub-pixels included in the reduced pixel P01 generated by the reduced image generation unit 85 in units of sub-pixels.

  The preprocessing unit 71 includes a luminance data generation unit 71a and a luminance data setting unit 71b. The luminance data generation unit 71a acquires image data of the original image that has been halved in the vertical direction (vertical) from the reduced image generation unit 85, and the luminance of each subpixel in the reduced pixel P01 based on the acquired image data A processing unit that generates data.

  Also, the luminance data setting unit 71b outputs the luminance data for each subpixel generated by the luminance data generation unit 71a as pixel control data to the reduced image generation unit 85, thereby setting the luminance of each subpixel in the reduced pixel P01. A processing unit to be set.

  Here, with reference to FIG. 6 and FIG. 7, the luminance data generation procedure No. 1 and No. 2 by the luminance data generation unit 71a will be described. FIG. 6 and FIG. 7 are diagrams showing a luminance data generation procedure No. 1 and No. 2 by the luminance data generation unit 71a in the present embodiment.

  Here, a case where the original image is reduced by a factor of 1/2 in the horizontal direction will be described as an example. As illustrated in FIG. 6, when the luminance data generation unit 71a acquires the image data of the original image, the two target pixels P0 that are adjacent in the horizontal direction as a reduction target from the pixel column that forms one horizontal line of the original image, Select P1.

  The luminance data generation unit 71a uses the luminance data of a predetermined number of pixels including at least the target pixels P0 and P1 among a plurality of pixels arranged on the same horizontal line as the target pixels P0 and P1, Luminance data for each of the three sub-pixels constituting the reduced pixel P01 generated from the pixels P0 and P1 is generated.

  Specifically, the luminance data generation unit 71a has a center on a vertical line X1 that is a boundary line between the pixel P-1 and the target pixel P0 using the luminance data of 6 pixels from P-3 to P2. Generate virtual subpixels.

  In addition, the luminance data generation unit 71a generates a virtual subpixel having a center on the vertical line X0 that is a boundary line between the target pixels P0 and P1, using the luminance data of 6 pixels from P-2 to P3. .

  In addition, the luminance data generation unit 71a generates a virtual sub-pixel having a center on the vertical line X2 that is a boundary line between the target pixel P1 and the pixel P2, using the luminance data of 6 pixels from P-1 to P4. To do. Here, it is assumed that the three virtual sub-pixels are present at equidistant intervals in the horizontal direction.

  Then, the luminance data generation unit 71a includes the distances to the sub-pixels corresponding to R among the six pixels from the vertical line X1 to P-3 to P2, and the luminance data of the six pixels from P-3 to P2. Are used to calculate the luminance data Yr of the virtual pixel centered on the vertical line X1.

  Also, the luminance data generation unit 71a includes the distance to each sub-pixel corresponding to G among the six pixels from the vertical line X0 to P-2 to P3, and the luminance data of the six pixels from P-2 to P3. Are used to calculate the luminance data Yg of the virtual pixel centered on the vertical line X0.

  In addition, the luminance data generation unit 71a includes the distance to each subpixel corresponding to B among the six pixels from the vertical line X2 to P-1 to P4, and the luminance data of the six pixels from P-1 to P4. Are used to calculate the luminance data Yb of the virtual pixel centered on the vertical line X2.

  Then, the luminance data setting unit 71b outputs the three types of luminance data Yr, Yg, and Yb calculated by the luminance data generation unit 71a to the reduced image generation unit 85 as pixel control data, thereby constituting the components of the reduced pixel P01. The luminance data of each subpixel is set in subpixel units.

  Thereby, the luminance data Yr is set as the luminance data of the sub-pixel corresponding to R in the reduced pixel P01, and the luminance data Yg is set as the luminance data of the sub-pixel corresponding to G in the reduced pixel P01. Among them, luminance data Yb is set as the luminance data of the sub-pixel corresponding to B.

  In the present embodiment, the case where three types of luminance data Yr, Yg, and Yb are calculated using the luminance data of 6 pixels including the target pixels P0 and P1 has been described as an example. Three types of luminance data Yr, Yg, Yb may be calculated using luminance data of an arbitrary number of pixels including P0 and P1.

  Further, in the present embodiment, in order to calculate three types of luminance data Yr, Yg, Yb, a case where the selected 6 pixel group is selected by sliding one pixel at a time among the 8 pixels P-3 to P4 is exemplified. As mentioned above, the slide amount of the 6-pixel group to be selected is not limited to one pixel at a time.

In this embodiment, three types of luminance data Yr, Yg, and Yb to be set for the reduced pixel P01 are calculated by an interpolation process using the following Lanczos3 function.
Lanczos3 (X) = sinc (πX) × sinc (πX / 3), −3 <X <3
= 0, X ≧ 3, X ≦ −3

  Here, with reference to FIG. 7, a procedure for calculating three types of luminance data Yr, Yg, and Yb to be set for the reduced pixel P01 by an interpolation process using the Lanczos3 function will be described. As shown in FIG. 7A, the Lanczos3 function takes the maximum value of Lanczos3 (X) when X is 0, and the value of Lanczos3 (X) converges to 0 as X approaches 3. Have nature.

  In the present embodiment, by using the property of the Lanczos3 function, three types of luminance data Yr, Yg, Yb to be set for each subpixel of the reduced pixel P01, that is, luminance data of three virtual pixels are calculated. .

  Specifically, as shown in FIG. 7B, when calculating the luminance data Yr of the virtual pixel centered on the vertical line X1 shown in FIG. 6, the origin of the horizontal axis X (X is 0). The point) is aligned with the vertical line X1. The vertical axis is a coefficient by which the luminance of the pixel used for calculation of the luminance data Yr is multiplied.

  Here, the value of X is a value normalized by the width of each target pixel. That is, a point where X is 1 or -1 is a point where the distance from the vertical line X1 matches the width. That is, each point on the graph shown in FIG. 7B corresponds to each subpixel corresponding to R among the pixels P-3 to P2. For example, the point having the shortest distance to the vertical line X1 on the graph shown in FIG. 7B corresponds to the sub-pixel corresponding to R in the target pixel P0.

  Then, the luminance data generation unit 71a uses the luminances of the six pixels from the pixels P-3 to P2 and the coefficient corresponding to the vertical axis of each point on the graph shown in FIG. Is calculated.

  That is, the luminance data generation unit 71a calculates a coefficient corresponding to the distance from each subpixel corresponding to R to the vertical line X1 in each pixel P-3 to P2, for each luminance of the pixels P-3 to P2. The luminance data Yr is calculated by multiplying and adding each multiplication result.

  That is, the luminance data generation unit 71a according to the present embodiment does not consider the position of each pixel to be referred to when calculating the luminance data Yr, but each R corresponding to R in each pixel to be referred to. Considers the position of sub-pixels. Accordingly, the luminance data Yr is luminance data reflecting the luminance change at the position of each sub-pixel corresponding to R among the pixels P-3 to P2.

  Further, as shown in FIG. 7C, when calculating the luminance data Yg of the virtual pixel centered on the vertical line X0 shown in FIG. 6, the origin of the horizontal axis X (the point where X becomes 0) is set. Match with the vertical line X0. The vertical axis is a coefficient by which the luminance of the pixel used for calculation of the luminance data Yg is multiplied.

  Here, the value of X is a value normalized by the width of each target pixel. That is, a point where X is 1 or -1 is a point where the distance from the vertical line X0 matches the width. That is, each point on the graph shown in FIG. 7C corresponds to each subpixel corresponding to G among the pixels P-2 to P3. For example, among the two points closest to the vertical line X0 on the graph shown in FIG. 7C, a point existing in the region of X <0 corresponds to a subpixel corresponding to G in the target pixel P0. The points existing in the region of X> 0 correspond to the subpixels corresponding to G in the target pixel P1.

  Then, the luminance data generation unit 71a uses the luminance of each of the six pixels from the pixels P-2 to P3 and the coefficient corresponding to the vertical axis of each point on the graph shown in FIG. Is calculated.

  That is, the luminance data generation unit 71a calculates a coefficient corresponding to the distance from each subpixel corresponding to G to the vertical line X0 in each pixel P-2 to P3 for each luminance of the pixels P-2 to P3. The luminance data Yg is calculated by multiplying and adding each multiplication result.

  That is, the luminance data generation unit 71a according to the present embodiment does not consider the position of each pixel to be referred to when calculating the luminance data Yg, but each G corresponding to G in each pixel to be referred to. Considers the position of sub-pixels. Accordingly, the luminance data Yg is luminance data reflecting the luminance change at the position of each sub-pixel corresponding to R among the pixels P-2 to P3.

  Further, as shown in FIG. 7D, when calculating the luminance data Yb of the virtual pixel centered on the vertical line X2 shown in FIG. 6, the origin of the horizontal axis X (the point where X becomes 0) is set. Match with the vertical line X2. The vertical axis is a coefficient by which the luminance of the pixel used for calculation of the luminance data Yb is multiplied.

  Here, the value of X is a value normalized by the width of each target pixel. That is, a point where X is 1 or -1 is a point where the distance from the vertical line X2 matches the width. That is, each point on the graph shown in FIG. 7D corresponds to each subpixel corresponding to B among the pixels P-1 to P4. For example, the point having the shortest distance to the vertical line X2 on the graph shown in FIG. 7D corresponds to the sub-pixel corresponding to B in the target pixel P1.

  Then, the luminance data generation unit 71a uses the luminance of each of the six pixels from pixels P-1 to P4 and the coefficient corresponding to the vertical axis of each point on the graph shown in FIG. Is calculated.

  That is, the luminance data generation unit 71a calculates a coefficient corresponding to the distance from each subpixel corresponding to B to the vertical line X2 among the pixels P-1 to P4 for each luminance of the pixels P-1 to P4. The luminance data Yb is calculated by multiplying and adding each multiplication result.

  That is, the luminance data generation unit 71a according to the present embodiment does not consider the position of each pixel to be referred to when calculating the luminance data Yb, but each pixel corresponding to B in each pixel to be referred to. Considers the position of sub-pixels. Accordingly, the luminance data Yb is luminance data reflecting the luminance change at the position of each sub-pixel corresponding to B among the pixels P-1 to P4.

  Returning to the description of FIG. 5, the post-processing unit 72 will be described. When the post-processing unit 72 adjusts the luminance of the three sub-pixels constituting the reduced pixel P01 individually in units of sub-pixels, there is a possibility that image quality deterioration called coloring may occur in the reduced image. In addition, the processing unit performs pixel control for reducing occurrence of coloring.

  The post-processing unit 72 includes a red reduction unit 72a, a yellow reduction unit 72b, an edge correction unit 72c, and a vertical line correction unit 72d.

  The red reduction unit 72a detects pixels that may be colored red at a position where white is originally displayed in the reduced image, and individually adjusts the luminance of predetermined sub-pixels constituting the detected pixels. It is a processing unit that reduces red color and displays it as white.

  The yellow reduction unit 72b detects pixels that may be colored yellow at a position where white is originally displayed in the reduced image, and individually adjusts the luminance of predetermined sub-pixels constituting the detected pixels. It is a processing unit that reduces yellow color development and displays it as white.

  The edge correction unit 72c detects two pixels existing at a light / dark boundary in the reduced image as edge regions, and pixel control data for adjusting the luminance of the sub-pixels constituting the lower luminance pixels in the detected edge region Is a processing unit that outputs to the reduced image generation unit 85. In other words, the edge correction unit 72c is a processing unit that suppresses a decrease in contrast due to coloring that occurs in the edge region.

  The vertical line correction unit 72d detects a thin vertical line (vertical line) with a light shade that exists in a background image with a dark shade in the reduced image, and sets the luminance of each subpixel of the pixels constituting the detected vertical line as a subpixel. This is a processing unit that outputs pixel control data for adjustment in units to the reduced image generation unit 85. That is, the vertical line correction unit 72d is a processing unit that reduces coloring that occurs in the vertical line.

  Here, with reference to FIG. 8 and FIG. 9, a cause of coloring and a method for reducing coloring will be described. FIG. 8 is a diagram showing a cause of coloring that occurs in the edge region and the vertical line and a method for reducing coloring, and FIG. 9 shows a cause of coloring caused by the arrangement order of the subpixels selected as the reduced pixels P01. It is a figure which shows the reduction method with coloring.

  Here, referring to FIG. 8, first, the cause of the coloring that occurs in the edge region and the vertical line and the method for reducing the coloring will be described, and then the sub pixel selected as the reduced pixel P01 will be described with reference to FIG. The cause of coloring and the method for reducing coloring according to the pixel arrangement order will be described.

  As shown in FIG. 8A, for example, in the case of a reduced image in which white is displayed with one pixel on a black background, luminance adjustment in units of subpixels must be performed for each subpixel of the pixel displaying white. For example, the luminance of all subpixels corresponding to RGB for displaying white is maximized.

  On the other hand, in consideration of the luminance of the pixel corresponding to black constituting the background of the pixel corresponding to white, when the luminance of the pixel corresponding to white is adjusted in sub-pixel units, as shown in FIG. The luminance of the subpixel on the side close to the background will decrease.

  In the example shown in FIG. 8B, it can be seen that the luminance of the sub-pixel corresponding to B close to the background and the sub-pixel corresponding to G in RGB is lower than the sub-pixel corresponding to R.

  As described above, when the luminance of the sub-pixels corresponding to G and B is lower than that of R, in the reduced image, coloring that appears to be reddish to the human eye for pixels that should originally be white occurs. Such coloring is not recognized as coloring by human eyes when, for example, one or two pixels displaying white in a black background appear continuously in the vertical direction. However, when a large number of pixels that display white appear continuously in the vertical direction to form vertical lines, they are recognized as colored by human eyes.

  For this reason, the vertical line correction unit 72d of the present embodiment has a predetermined number (for example, 3 pixels) or more of pixels having a luminance higher than the predetermined upper limit in the background image of the luminance lower than the predetermined lower limit in the reduced image. Detect vertical lines that appear continuously in the direction.

  Then, the vertical line correction unit 72d increases the brightness of the other sub-pixels so as to approach the brightness of the sub-pixel having the maximum brightness among the three sub-pixels that are constituent elements of the pixels constituting the detected vertical line. To perform the process.

  Specifically, as illustrated in FIG. 8C, the vertical line correction unit 72d includes a sub-pixel corresponding to R having the maximum luminance among the three sub-pixels that are constituent elements of the pixel configuring the vertical line. The luminance of the sub-pixel corresponding to G and the luminance of the sub-pixel corresponding to B are increased so as to approach the luminance of. Thereby, it can suppress that coloring arises in a vertical line part.

  Further, coloring by performing luminance adjustment in units of sub-pixels may occur in an edge region that is a boundary between light and dark in a reduced image. That is, in the edge region, when the difference in luminance set in two pixels adjacent to the horizontal direction constituting the edge exceeds a predetermined range, when the luminance is adjusted in units of sub-pixels, the pixel having the higher luminance is described above. As with the vertical lines, coloring occurs.

  For this reason, when the edge correction unit 72c according to the present embodiment detects an edge region where the difference in luminance set between adjacent pixels exceeds a predetermined range, the edge correction unit 72c configures a pixel on the higher luminance side in the edge region. Color reduction processing is performed on the pixels in the same manner as the vertical line correction unit 72d.

  Specifically, the edge correction unit 72c adjusts the luminance values of the other subpixels so as to approach the luminance value of the subpixel having the highest luminance among the three subpixels constituting the higher luminance side pixel in the edge region. Process to raise.

  Further, in the display device according to the present embodiment, when a reduced image is displayed on the TFT panel 82 for performing sub-pixel rendering, as a combination of three sub-pixels used as one pixel, as shown in FIG. There are three types of combinations, GBR and BRG.

  Here, a physical interval called a gap exists between the three sub-pixels constituting the pixel. Of the intervals between sub-pixels, the intervals between GB and RG are unlikely to cause coloring, but the intervals between BRs are likely to cause coloring.

  More specifically, when white is displayed with subpixels arranged in the order of RGB as one pixel, it is recognized as white by human eyes without any problem.

  On the other hand, when white is displayed with an area where subpixels are arranged in the order of GBR as one pixel, there is a gap between the subpixels corresponding to BR, so that the human eye has a mixed color of GB. Since certain cyan and R are visually recognized individually, white is recognized as reddish.

  Such coloring due to the interval between the sub-pixels is noticeable when the reduced image is viewed from an oblique direction. Therefore, in a display device that outputs video data to a display device that is expected to be viewed from an oblique direction, such as a display device mounted on a vehicle, it is necessary to reduce coloring due to the interval between subpixels. .

  For this reason, the red reduction unit 72a according to the present embodiment selects subpixels arranged in the order of GBR as subpixels constituting one pixel, and exceeds a predetermined upper limit for the selected subpixel. When the luminance is set, a process of reducing the luminance of the sub-pixel corresponding to R as the interval between the sub-pixels corresponding to BR is longer is performed.

  Thereby, when sub-pixels arranged in the order of GBR are selected as one pixel and white is displayed, occurrence of coloring can be suppressed.

  On the other hand, when white is displayed with the subpixels arranged in the BRG order as one pixel, a mixed color of B and RG is present in the human eye due to the presence of a space between the subpixels corresponding to BR. Since yellow, which is, is visually recognized individually, white is recognized as yellowish.

  For this reason, the yellow reduction unit 72b according to the present embodiment selects the subpixels arranged in the BRG order as the subpixels constituting one pixel, and exceeds a predetermined upper limit value with respect to the selected subpixels. When the luminance is set, the luminance of the sub-pixel corresponding to R and the sub-pixel corresponding to G is reduced as the interval between the sub-pixels corresponding to BR is longer.

  Thereby, when sub-pixels arranged in the order of BRG are selected as one pixel and white is displayed, occurrence of coloring can be suppressed.

  Next, a specific operation of the display device according to the present embodiment will be described with reference to FIGS. In the drawing, only the processing procedure related to sub-pixel control executed by the pixel control unit 87 among the processing executed by the display device is shown. FIG. 10 is a flowchart showing a processing procedure of the pre-processing unit 71 included in the subpixel control unit 87, and FIG. 11 is a flowchart showing a processing procedure of the post-processing unit 72 included in the subpixel control unit 87.

  As illustrated in FIG. 10, when the preprocessing unit 71 acquires image data reduced by a factor of 1/2 in the vertical direction (vertical) from the reduced image generation unit 85 (step S101), the preprocessing unit 71 arranges the image data in the horizontal direction as reduction targets. The selected plurality of pixels (target pixels P0 and P1) are selected, and the brightness data for the three types of sub-pixels constituting the reduced pixel P01 are generated from the brightness data of the plurality of pixels including the selected target pixels P0 and P1. (Step S102).

  Subsequently, the preprocessing unit 71 outputs the generated three types of luminance data as pixel control data to the reduced image generation unit 85, whereby the three types of luminance data generated in step S102 constitute each reduced pixel P01. The luminance data for the subpixel is set (step S103), and the process is terminated.

  Then, the preprocessing unit 71 selects all the pixels acquired from the reduced image generation unit 85 as the target pixels P0 and P1, and selects all the reduced pixels P01 that constitute the reduced image generated from the selected target pixels P0 and P1. The processes in steps S101 to S103 are repeatedly executed until the setting of luminance data for the subpixel is completed.

  On the other hand, as illustrated in FIG. 11, when the post-processing unit 72 acquires the image data (reduced image data) of the reduced image from the reduced image generation unit 85, the post-processing unit 72 configures pixels in which luminance exceeding a predetermined upper limit value is set. It is determined whether or not the arrangement (arrangement) of subpixels to be performed is GBR (step S201).

  If the post-processing unit 72 determines that the arrangement of sub-pixels is GBR (step S201: Yes), the longer the interval between sub-pixels corresponding to BR, the lower the luminance of the sub-pixel corresponding to R. (Step S202), and the process proceeds to Step S203.

  Further, when the post-processing unit 72 determines that the sub-pixel arrangement is not GBR (step S201: No), the sub-pixel arrangement constituting the pixel in which the luminance exceeding the predetermined upper limit value is set is BRG. Whether or not (step S205).

  When the post-processing unit 72 determines that the arrangement of the sub-pixels is BRG (step S205: Yes), the longer the interval between the sub-pixels corresponding to BR, the longer the interval between the sub-pixels corresponding to R and G. The brightness is reduced (step S206), and the process proceeds to step S203.

  If the post-processing unit 72 determines that the sub-pixel arrangement is not BRG (step S205: No), the post-processing unit 72 moves the process to step S203. In step S203, the post-processing unit 72 determines whether an edge exists in the reduced image.

  Then, when the post-processing unit 72 determines that an edge exists (step S203: Yes), with respect to the pixel having the higher luminance at the edge, the sub-pixel having the highest luminance among R, G, and B is used as a reference. A process for increasing the brightness of the other sub-pixels so as to approach the reference is performed (step S204), and the process ends.

  Further, when the post-processing unit 72 determines that no edge exists (step S203: No), one pixel whose luminance exceeds a predetermined upper limit value in the background in which the luminance is lower than the predetermined lower limit value in the reduced image ( Hereinafter, it is determined whether a predetermined number (for example, 3 pixels) or more are continuously present in the vertical direction (referred to as “white dots”) (step S207).

  Then, when the post-processing unit 72 determines that the white spot is present continuously three or more pixels vertically (step S207: Yes), for the pixels constituting the white spot, among R, G, and B, With the subpixel having the highest luminance as a reference, processing is performed to increase the luminance of other subpixels closer to the reference (step S204), and the processing is terminated. Further, when the post-processing unit 72 determines that the white spots do not exist continuously for three or more pixels vertically (step S207: No), the processing ends.

  As described above, in the display device according to the present embodiment, for example, a plurality of target pixels P0 and P1 are selected as reduction targets from the original image, and a plurality of pixels arranged in the horizontal direction including the target pixels P0 and P1 are selected. Based on the luminance data, three types of luminance data reflecting the difference in luminance between the target pixels P0 and P1 are generated and set as the luminance data of each sub-pixel constituting the reduced pixel P01.

  Therefore, the reduced pixel P01 can reproduce the difference in luminance between the target pixels P0 and P1 depending on the difference in luminance between the sub-pixels. Therefore, according to the display device according to the present embodiment, it is possible to reproduce a subtle color change (gradation) existing in the original image with higher reproducibility than the conventional image processing technique.

  In the display device according to the present embodiment, the pixel control unit 87 is provided when there is a possibility that coloring may occur in the reduced image by adjusting the luminance of each subpixel of the reduced pixel P01 in units of subpixels. Occurrence of coloring can be prevented in advance by the pixel control executed by the post-processing unit 72.

  In this embodiment, the case where one reduced pixel P01 is generated from the two target pixels P0 and P1 has been described as an example. However, the present invention can reduce one reduced pixel from any number of target pixels P0 and P1. The present invention can also be applied to the case where the pixel P01 is generated.

  For example, when one reduced pixel P01 is generated from three target pixels, each luminance data of the three target pixels is set as luminance data of each sub-pixel constituting the reduced pixel P01.

  When one reduced pixel P01 is generated from the four target pixels, three virtual pixels reflecting the difference in luminance of each target pixel are generated from the four target pixels, and three types of the generated three virtual pixels are generated. Luminance data is set as luminance data of each sub-pixel constituting the reduced pixel P01.

  That is, the present invention finally generates the same number of luminance data as the number of sub-pixels in the reduced pixel from the luminance data of a plurality of pixels arranged in the horizontal direction including at least the target pixel, and reduces the generated luminance data. By setting the luminance data of each sub-pixel of the pixel, it is possible to suppress the image quality deterioration of the reduced image.

  In this embodiment, the case where the number of subpixels constituting the reduced pixel is 3 has been described as an example. However, the number of subpixels constituting the reduced pixel is not limited to 3.

  As described above, the image processing apparatus and the image processing method according to the present invention are useful when it is desired to improve the image quality of a reduced image by minimizing image quality degradation that occurs when the image is reduced. This is suitable when you want to improve the quality of the displayed reduced image.

DESCRIPTION OF SYMBOLS 1 In-vehicle apparatus 11 Navigation engine 12 TV tuner 13 DVD deck 14 Rear camera 15 Audio microcomputer 16 Drawing part 17 Image | video switching part 18 Display apparatus 71 Pre-processing part 72 Post-processing part 71a Luminance data generation part 71b Luminance data setting part 72a Red reduction part 72b Yellow reduction unit 72c Edge correction unit 72d Vertical line correction unit 81 Power supply 82 TFT panel 83 Microcomputer processing unit 84 LVDS receiver 85 Reduced image generation unit 86 Gradation processing unit 87 Pixel control unit 88 Timing control unit 89 Memory P01 Reduced pixel P0, P1 target pixel

Claims (4)

An image processing apparatus for processing an image composed of pixels including a predetermined number of subpixels,
The reduced image is generated from the original image by associating a plurality of target pixels extracted from the original image to be reduced with one reduced pixel corresponding to the plurality of target pixels on the reduced image to be reduced Reduced image generation means for
A pixel group that is continuous in the same direction as the sub-pixel arrangement direction and includes at least the plurality of target pixels is selected from the original image, and is included in the relative position between the pixels included in the pixel group and the pixel group. Generating means for generating the same number of luminance data based on the luminance data of each pixel,
Brightness data setting means for setting each brightness data generated by the generating means as brightness data of each sub-pixel in the reduced pixel;
An image processing apparatus comprising: a display control unit that displays a reduced image in which the luminance data is set by the luminance data setting unit on a predetermined display unit. An edge region detection unit that detects an edge region in which the difference in luminance between adjacent pixels in the arrangement direction exceeds a predetermined range in the reduced image generated by the reduced image generation unit;
Among the sub-pixels constituting the higher-luminance pixel in the edge region detected by the edge region detection means, the luminance of the pixel with the higher luminance is determined with reference to the luminance of the sub-pixel with the highest luminance. The image processing apparatus according to claim 1, further comprising an edge correction unit configured to increase the luminance of the sub-pixels other than the sub-pixel having the highest luminance among the sub-pixels so as to approach the reference. In the reduced image generated by the reduced image generating means, there is a pixel whose luminance exceeds a predetermined upper limit in the background image whose luminance is lower than a predetermined lower limit, and the pixel is orthogonal to the arrangement direction. A vertical line area detecting means for detecting a vertical line area continuously present in a predetermined number or more in the direction;
In the vertical line area detected by the vertical line area detection means, the pixel having the higher luminance with reference to the luminance of the sub-pixel having the highest luminance among the pixels whose luminance exceeds the predetermined upper limit value 3. The image according to claim 1, further comprising a vertical line correction unit configured to increase the luminance of the sub-pixels other than the sub-pixel having the highest luminance among the sub-pixels so as to approach the reference. 4. Processing equipment. An image processing method for processing an image composed of pixels including a predetermined number of subpixels,
The reduced image is generated from the original image by associating a plurality of target pixels extracted from the original image to be reduced with one reduced pixel corresponding to the plurality of target pixels on the reduced image to be reduced A reduced image generation step,
A pixel group that is continuous in the same direction as the sub-pixel arrangement direction and includes at least the plurality of target pixels is selected from the original image, and is included in the relative position between the pixels included in the pixel group and the pixel group. Generating the same number of luminance data as the predetermined number based on the luminance data of each pixel,
A luminance data setting step for setting each luminance data generated by the generating step as luminance data of each sub-pixel in the reduced pixel;
A display control step of displaying a reduced image in which the luminance data is set by the luminance data setting step on a predetermined display unit.

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