JP2009204828A - Image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent occurrence of a pseudo contour when performing the subtractive color processing of image data in which a gradation value is concentrated in a specific range and handling them. <P>SOLUTION: The image display device includes: a division point information extraction part 101 for inputting source image data whose respective color components are expressed by at least two bits and extracting division point information to be a point of changing a gradation width for the source image data; a division point information storage memory 102 for storing the division point information; a pseudo gradation processing part 103 for color-subtracting the source image data to subtractive color image data using the division point information; a frame buffer 104 for storing the subtractive color image data; and a gradation correction part 105 for generating display image data from the division point information and the subtractive color image data. The pseudo gradation processing part 103 performs the subtractive color processing so as to equalize the respective gradation widths in the range of a large gradation value and in the range of a small gradation value centering on the division point. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image display device that displays an image such as a digital moving image.

  In the above-mentioned image display device, with the recent increase in demand for higher image quality, the resolution of image display continues to increase, and with this increase in display memory usage, the reduction of display memory becomes an increasingly important factor. It's getting on. On the other hand, further power saving is desired in portable device applications.

  In a conventional image display apparatus, Patent Document 1 exists as a method for reducing display memory while maintaining high quality. Patent Document 1 discloses an example in which color reduction is performed so that the number of gradations reflects the luminance contribution of each RGB component.

  That is, in the above color reduction example, in consideration of human visual sensitivity and the characteristics of the display device, a component having a high luminance contribution is provided with a larger number of gradations to improve the display quality, and the luminance contribution is low. For the component, the amount of information is saved by assigning a smaller number of gradations.

More specifically, in the luminance conversion coefficient of the CRT using ITU-R BT709, R = 0.213, G = 0.715, and B = 0.072, and the luminance contribution of G is about B The document concludes that R: G: B = 2: 4: 1 is a desirable distribution ratio. For example, in order to display 4096 colors using 12-bit color components, the bit distribution is distributed as R = 4 bits, G = 5 bits, and B = 3 bits.
JP 2002-221950 A

  However, in the image display device of Patent Document 1, the number of gradations of each RGB component is unevenly distributed, whereas the gradation width of each RGB component is almost equally divided in all ranges, and the color reduction is performed. is doing.

  FIG. 13 is a diagram showing a color reduction result obtained by a conventional color reduction process. In this figure, an original image having 8 bits (256 gradations) of gradations for a certain color component is reduced to a color-reduced image having 4 bits (16 gradations) of gradations.

  In this color reduction process, even if processing is performed using the dither method or the diffusion error method, the 256 gradations of the input value are assigned almost evenly to the 16 gradations. The input gradation values 16 to 31 are rounded to the output gradation value 1 and replaced with the value 0. The same applies to the input gradation value 32 and later. This means that when the gradation values in the image data are concentrated in a specific range, the necessary gradation change cannot be obtained, and a problem such as the appearance of a pseudo contour occurs, resulting in deterioration in image quality. There was a case.

  Although this example is an example in which 8 bits are reduced to 4 bits, the present invention is also applicable to the case of reducing colors between other bits without departing from the gist thereof.

  An image display device according to the present invention receives, as input, original image data in which each color component is expressed by at least 2 bits, and extracts point information for changing the gradation width with respect to the original image data, Point information storage means for storing point information, color reduction means for reducing original image data to color reduction image data using the point information, color reduction image data storage means for storing the color reduction image data, point information and color reduction Display image data generating means for generating display image data from the image data, and image display means for displaying the display image data generated by the display image generating means are provided.

  In the present invention, a preferred aspect is that the color reduction means performs color reduction so that the gradation widths are equal in a range where the gradation value is large and a small range around the point.

  In this aspect, the display quality can be improved by reducing the memory and increasing the number of gradations assigned to the region with a large or small gradation value.

  In the present invention, it is preferable that the color reduction unit uses the point information as maximum resolution range information including vertex information and width information, and the gradation widths are equal within and outside the range of the maximum resolution range information. So that the color is reduced.

  In this aspect, the display quality can be improved by reducing the memory and increasing the number of gradations assigned to an arbitrary range where the gradation values are concentrated.

  In this invention, a preferable aspect is that the said point information extraction part extracts point information with respect to each of the coordinate range information which consists of several coordinate ranges with respect to the said original image data.

  In this aspect, the display quality can be improved more effectively by reducing the memory and assigning the gradation to the necessary range in image area units.

  In the present invention, a preferred mode is that the effective range of the maximum resolution range information is selected from either the range of the maximum resolution range information, the range outside the range, or both, and the gradation value is assigned.

  In this aspect, the display quality can be improved more effectively by reducing the memory and not assigning the gradation to the unnecessary range.

  According to the image display device of the present invention, it is possible to easily improve display quality and suppress power consumption while suppressing memory consumption by effective color reduction processing.

  Hereinafter, embodiments of the image display apparatus and the like will be described with reference to the drawings. In addition, since the component which attached | subjected the same code | symbol in embodiment performs the same operation | movement, description may be abbreviate | omitted again.

(Embodiment 1)
An image display apparatus according to Embodiment 1 of the present invention will be described.

  FIG. 1 is a block diagram of an image display apparatus according to the first embodiment.

  The image display device 1 includes a division point information extraction unit 101, a division point information storage memory 102, a pseudo gradation processing unit 103, a frame buffer 104, a gradation correction unit 105, and an image display unit 106.

  The division point information extraction unit 101 receives, as point information storage means, original image data in which each color component is expressed by at least two bits or more as point information serving as a point for changing the gradation width with respect to the original image data. Extract dividing point information.

  The division point information storage memory 102 stores division point information.

  When the original image data is reduced using the division point information to obtain the reduced color image data as the color reduction means, the pseudo gradation processing unit 103 has a small and large range of gradation values around the division point for each color reduction. The color is reduced so that the gradation widths are uniform in each range.

  The frame buffer 104 stores reduced color image data as a reduced color image data storage unit.

  The gradation correction unit 105 generates display image data from the division point information and the subtractive color image data as display image data generation means.

  The image display unit 106 displays display image data as display image data display means.

  Hereinafter, a specific operation of the image display apparatus in the present embodiment will be described.

  A conceptual diagram of the division point extraction process of the division point information extraction unit 101 is shown in FIG.

  The division point information extraction unit 101 extracts gradation values of each color component of RGB for each pixel as shown in FIG. 2B from the original image data (RGB) in FIG. As shown in FIG. 2 (d), the average value calculated using is used as the values of the dividing points μR, μG, and μB.

  The division point information extraction unit 101 stores the information of the division points μR, μG, and μB calculated in this way in the division point information storage memory 102.

  2B shows R component, G component, and B component as each color component (RGB) decomposed from the original image data (RGB), and FIG. 2C shows the number of gradations of R component, G component, and B component. FIG. 2 (d) shows the extraction of the dividing points μR, μG, and μB. In FIG. 2C, the number of gradations increases upward on the vertical axis, and the gradation value increases on the right side of the horizontal axis. The number of gradations on the vertical axis is the number of pixels having the same gradation value for each color component in the original image data (RGB) in FIG. In FIG. 2D, the dividing points μR, μG, μB indicate the average values of the gradation values for the respective color components, and R1, R2,..., Rn are the gradation values of the R components, G1, G2,. , Gn are G component gradation values, B1, B2,..., Bn are B component gradation values, and n is the number of gradation values.

  FIG. 3 is a conceptual diagram of the color reduction processing using the division points of the pseudo gradation processing unit 103.

  In FIG. 3, the division points μR, μG, and μB of the R component, G component, and B component stored in the division point information storage memory 102, and the levels of the R component, G component, and B component of the original image data (RGB), respectively. The comparison values 103a, 103b, and 103c compare the gradation values R, G, and B, respectively. If the gradation values R, G, and B of the original image data (RGB) are larger than the dividing points μR, μG, and μB as a result of the comparison, the gradation value p ′ before color reduction is calculated using the calculation formula 121. The gradation value p after color reduction is calculated. Further, when the gradation values R, G, and B of the original image data (RGB) are smaller than the dividing points μR, μG, and μB, the gradation value p ′ after the color reduction is compared with the gradation value p ′ before the color reduction using the calculation formula 122. The gradation value p is calculated respectively.

Tone value after subtractive color p = (Tone value before subtractive color p '/ Tone tone width d1) +2 ^m-1 (121)
Tone value p after color reduction = (tone value p ′ before color reduction / tone width d2) (122)
However, p is the gradation value after color reduction, p ′ is the gradation value before color reduction, d1 is (2 ⁿ −μ) / 2 ^m−1 , d2 = μ / 2 ^m−1 , and n is the original image data ( RGB) R component, G component, and B component bits, m is the R component, G component, and B component bits of the subtractive image, d1 and d2 are the gradation widths during subtractive color, and μ is the dividing point μR, μG and μB, and the subscripts R, G, and B are abbreviated. The same applies to the following. In this way, image data after color reduction (color-reduced image data) is configured by repeating the same processing on the gradation values (p ′) of all the pixels constituting the original image data (RGB) that is image data before color reduction. The gradation value (p) of all the pixels to be generated is generated. The generated color-reduced image data is stored in the frame buffer 104.

Next, an expression for generating display image data (P) to be displayed on the display screen from the subtractive color image data (p) using the division points of the gradation correction unit 105 is shown below. The subtractive point of each RGB color component is μ, the gradation value of each RGB color component of the reduced color image data is p, the gradation value of each RGB color component of the display image data is P, and the number of gradations of the display image is 2 ^n. When the number of gradations of data is 2 ^m (where n> m), the gradation width of the reduced color image data (p) is replaced with the gradation widths of d1 and d2 in the display image.

Therefore, when this is shown in the equation, if the gradation value after subtractive color is greater than 2 ^m-1 ,
d1 = (2 ⁿ −μ) / 2 ^m−1
Using this, the gradation value P of the display image is obtained.
P = d1 · (p−2 ^m−1 )
It becomes. On the other hand, if the gradation value after color reduction is less than 2 ^m-1 ,
d2 = μ / 2 ^m-1
Using this, the gradation value P of the display image is obtained.
P = d2 · p
It becomes.

  With respect to the conceptual diagram of FIG. 3, A indicates the gradation width of the display image, B indicates the gradation width of the subtractive color image, and as is clear by comparing the gradation widths of these two images, The gradation width of the color-reduced image is reduced for every d1, and the gradation width of the reduced-color image is reduced for every d2 at a gradation value smaller than the dividing point μ.

  The image generated in this way is displayed on the image display unit 106.

   FIG. 4 shows the effect of the subtractive color reduction processing using this embodiment. FIG. 4A shows the input gradation value on the horizontal axis and the output gradation value on the vertical axis. The input tone value is the tone value of the original image data (RGB), and the output tone value is the tone value of the subtractive color image data. FIG. 4B shows an example of gradation values of the original image data (RGB), and FIG. 4C shows an example of gradation values of the reduced color image data. In FIG. 4, original image data (RGB) in which there are many pixels having a gradation value larger than the dividing point μ is input, and fine color reduction processing is performed on an area having a large gradation value at the dividing point μ. This shows that the quality is improved with respect to most of the subtractive color image data (p).

  As described above, according to the present embodiment, it is possible to improve display quality by performing memory reduction by color reduction processing and assigning a large number of gradations to a region having a large gradation value or a region having a small gradation value.

Incidentally, according to this embodiment, the original image data, color-reduced image data, the display image data is set to the RGB color components, it is also applicable to the other components of the luminance component and color difference components, such as YC _b C _r .

  Further, according to the present embodiment, the average value is used in the dividing point extraction method, but it may be determined using a standard deviation indicating the degree of data dispersion.

  In addition, according to the present embodiment, the division point information extraction unit and the pseudo gradation processing unit may be implemented as a program or may be realized using a dedicated circuit.

(Embodiment 2)
In the present embodiment, an image display device will be described.

  FIG. 5 is a block diagram of the image display apparatus according to the second embodiment.

  The image display device 2 includes a maximum resolution range information extraction unit 201, a maximum resolution range information storage memory 202, a pseudo gradation processing unit 203, a frame buffer 204, a gradation correction unit 205, and an image display unit 206.

  The maximum resolution range information extraction unit 201 receives, as point information extraction means, original image data in which each color component is expressed by at least 2 bits or more, and vertex information that is a point for changing the gradation width with respect to the original image data; The maximum resolution range information consisting of width information is extracted.

  Here, the vertex information is one gradation value included in the image data, and is information indicating the center point of the maximum resolution range information. The width information is a difference between two gradation values included in the image data, and is information indicating the width of the maximum resolution range information. As described above, the maximum resolution range information is determined by the vertex information and the width information, and is defined as point information for color reduction so that the gradation widths are equal in and out of the range of the maximum resolution range information. be able to.

  The maximum resolution range information storage memory 202 stores maximum resolution range information as point information storage means.

  As the color reduction means, the pseudo gradation processing unit 203 uses the maximum resolution range information to reduce the original image data to the color-reduced image data so that the gradation widths are equal within and outside the range of the maximum resolution range information.

  The reason why the original image data is reduced to the color-reduced image data by using the maximum resolution range information so that the gradation widths are equalized within and outside the range of the maximum resolution range information is specifically required for gradation. This is for securing a large number of gradations in the range. By such color reduction processing, there is an advantage of suppressing deterioration in image quality after color reduction by dividing the number of gradations into a range where it is necessary and an unnecessary range. In particular, since the color reduction process is performed only at the dividing points in the first embodiment, a high effect is exhibited for a large or small range of gradation values, whereas in the second embodiment, in a range of arbitrary gradation values. Is more effective.

  The frame buffer 204 stores the reduced color image data.

  The gradation correction unit 205 generates display image data from the maximum resolution range information and the reduced color image data as display image data generation means.

  The image display unit 206 displays display image data as display image data display means.

  Hereinafter, a specific operation of the image display apparatus in the present embodiment will be described.

  A conceptual diagram of the maximum resolution range extraction processing of the maximum resolution range information extraction unit 201 is shown in FIG. 6 (a) to 6 (c) correspond to FIGS. 2 (a) to 2 (c). FIG. 6 (d) shows the extraction of the maximum resolution range in this embodiment. As shown in FIGS. 6B and 6C, the gradation values of the RGB color components are extracted in pixel units from the original image data (RGB) in FIG. 6A, and the extracted data is used. As shown in FIG. 6D, the average value (μ) and the value (2σ) obtained by doubling the standard deviation (σ) are calculated as vertex information (μ) and width information (2σ), respectively. To do.

  The average value (μ) and the double value (2σ) of the standard deviation (σ) are set as vertex information (μ) and width information (2σ), respectively, in which range of gradation values and in what proportion There is an advantage that it is possible to know whether the gradation values of the original image data are scattered and to assign the gradation values of the color-reduced image data finely to the range where the gradation values of the original image data are concentrated. In the first embodiment, since the gradation value is changed by using the average value as the dividing point μ, the gradation value after color reduction may not be appropriately assigned due to variation in the distribution of gradation values. In the second embodiment, the gradation values after color reduction can be more appropriately assigned corresponding to the variation in the distribution of gradation values by using the expressions of standard deviations σR, σG, and σB.

  In the formulas of standard deviations σR, σG, and σB in FIG. 6D, μR, μB, and μB are average values of the respective R components, G components, and B components, n is the number of gradation values, Ri is the gradation value of the R component, Gi is the gradation value of the G component, and Bi is the gradation value of the B component. σR is the standard deviation of the R component, σG is the standard deviation of the G component, and σB is the standard deviation of the B component. i is 1 to n.

In FIG. 6 (d), 68.27% of all gradation value data is distributed by setting the dividing points μR, μG, and μB as the centers and the left and right directions 2σR, 2σG, and 2σB. The maximum resolution range ({μ, 2σ} _R , {μ, 2σ} _G , {μ, 2σ} _B ) is a range that includes about 2/3 of the number of gradations, and is therefore in a range where gradation is necessary. On the other hand, there is an effect that the number of gradations can be efficiently allocated.

The maximum resolution range ({μ, 2σ} _R , {μ, 2σ} _G , {μ, 2σ} _B ) composed of such vertex (μ) and width (2σ) is calculated for each color component of RGB, and the maximum resolution range The information is stored in the information storage memory 202.

  A conceptual diagram of the color reduction processing using the maximum resolution range of the pseudo gradation processing unit 203 is shown in FIG.

In FIG. 7, the maximum resolution range information ({μ, 2σ} _R , {μ, 2σ} _G , {μ, 2σ} _B ) of the RGB color components stored in the maximum resolution range information storage memory 202 and the original image data The RGB gradation values are compared by the comparison units 203a, 203b, and 203c.

  As a result of the comparison, if the gradation value of the original image data is larger than the maximum resolution range, the gradation value after color reduction is calculated using the calculation formula 221. When the gradation value of the original image data is within the maximum resolution range, the gradation value after color reduction is calculated using the calculation formula 222. Further, when the gradation value of the original image data is smaller than the maximum resolution range, the gradation value after color reduction is calculated using the calculation formula 223.

Output gradation value = [(input gradation value−2σ) / d2] +2 ^m−1 (221)
Output gradation value = [input gradation value− (μ−σ)] / d1] + (μ−σ) / d2
... (222)

Output gradation value = input gradation value / d2 (223)
However, m is the number of bits of each color component of the subtractive color image, and d1 and d2 are the gradation widths during subtractive color.

  The significance of the calculation formulas 221, 222, and 223 will be described more clearly below.

  The same process is repeated for the gradation values of all the pixels of the original image data (RGB) to generate reduced color image data. The generated subtractive color image data is stored in the frame buffer 204.

  Next, an expression for generating display image data from subtractive color image data using the maximum resolution range of the gradation correction unit 205 is shown below.

The gradation value of each RGB color component of the reduced color image data is p, the gradation value of each RGB color component of the display image data is P, the number of gradations of the display image is 2 ^n, and the number of gradations of the reduced color image data is 2 ^m When the gradation width of the subtractive color image is within the display resolution range (μ, 2σ), it is replaced as d ₁ gradation width in the display image, while when it is outside the display resolution range (μ, 2σ). Assuming that it is replaced as a difference between d ₂ gradation values in the display image, when this is expressed by an equation, if it is larger than the display resolution range (μ, 2σ),
d2 = (2 ⁿ −2σ) / 2 ^m−1
Using this, the gradation value P of the display image is obtained.
P = 2σ + d2 (p−2 ^m−1 )
It becomes. In the case of display resolution range (μ, 2σ)
d1 = 2σ / 2 ^m-1
Using this, the gradation value P of the display image is obtained.
P = [(d2−d1) / d2] · (μ−σ) + d1 · p
It becomes. If it is smaller than the display resolution range (μ, 2σ),
d2 = (2 ⁿ −2σ) / 2 ^m−1
Using this, the gradation value P of the display image is obtained.
P = d2 · p
It becomes. However, n is the number of bits of each color component of the original image data (RGB).

 The image generated in this way is displayed on the image display unit 206.

  In FIG. 7, the area A represents the gradation width of the display image, and the area B represents the gradation width of the reduced color image.

  FIG. 8 shows the effect in the color reduction processing by the maximum resolution range using the present embodiment. FIGS. 8A to 8C correspond to FIGS. 4A to 4C. In FIG. 8, the original image data in which there are many pixels whose gradation values are close to the middle is input, and fine color reduction processing is performed on the area within the maximum resolution range by the maximum resolution range {μ, 2σ}. This shows that the quality is improved with respect to most of the subtractive color image data.

  Compared to those in FIG. 4, FIG. 8 not only exhibits a high effect for a large or small range of gradation values, but also exhibits a high effect in an arbitrary gradation value range. Has improved. In FIG. 4, since the color is reduced using the division point information, the gradation value after the color reduction may not be appropriately assigned due to the dispersion of the gradation value distribution, whereas in FIG. 8, the maximum resolution range is shown. By using information to reduce the color, it is possible to know in what range the gradation value is scattered at what ratio, and the color-reduced image data is finely divided into the range where the gradation value of the original image data is concentrated. This is because gradation values can be assigned.

  As described above, according to the present embodiment, it is possible to improve display quality by performing memory reduction by color reduction processing and assigning gradations to a necessary range.

Incidentally, according to this embodiment, the original image data, color-reduced image data, the display image data is set to the RGB color components, it is also applicable to the other components of the luminance component and color difference components, such as YC _b C _r .

  Further, according to the present embodiment, the standard deviation indicating the degree of data dispersion is used for the maximum resolution range extraction method, but other methods may be used.

  Further, according to the present embodiment, the maximum resolution range information extraction unit and the pseudo gradation processing unit may be implemented as a program or may be realized using a dedicated circuit.

(Embodiment 3)
The image display apparatus in this embodiment will be described.

  FIG. 9 is a block diagram of the image display device according to the third embodiment.

  The image display device 3 includes a coordinate range information extraction unit 307 and a coordinate range information storage memory 308 in the image display device 1.

  The coordinate range information extraction unit 307 extracts a plurality of coordinate range information from the original image data.

   Here, the coordinate range information indicates a rectangular area in the original image data, and is a range specified by the upper left coordinate value and the lower right coordinate value.

  The coordinate range information storage memory 308 stores coordinate range information.

  The features of the third embodiment are as follows. That is, in Embodiments 1 and 2, point information is extracted for the entire original image data, but in Embodiment 3, the original image data is divided into a plurality of coordinate ranges, and points are assigned to each of the divided areas. It differs from those of Embodiments 1 and 2 in that information is extracted, and is characterized in that different color reduction is performed for each coordinate range.

  Hereinafter, a specific operation of the image display apparatus in the present embodiment will be described.

  A conceptual diagram of the coordinate range extraction process of the coordinate range information extraction unit 307 is shown in FIG.

  In FIG. 10, a boundary line for dividing an image is provided for the original image data, and the gradations of the RGB color components of the original image data in the upper coordinate range (a) and the lower coordinate range (b) of the boundary line are provided. Extract each value.

  The average value (μA, μB) of the extracted data is calculated, and the difference is obtained.

  Here, the image is divided in FIG. 10 (the original image data is divided into a plurality of coordinate ranges in the Y-axis direction, and the boundary row is separated into regions having different distribution states of gradation values included in the original image data. The coordinate range (a) above the boundary line is the origin (0,0) of the original image data, the X axis is the width of the original image data, and the Y axis is The range from the boundary line that divides the image. The lower coordinate range is the range from 0 on the X axis to the width of the original image data, and the range from the boundary line that divides the image to the height of the original image on the Y axis. The difference is the difference between the average values of the gradation values of the pixels included in the two coordinate ranges.

  Next, the boundary line is moved, and similarly, gradation values of RGB color components of the original image data in the upper coordinate range (a) and lower coordinate range (b) of the boundary line are extracted.

  Here, moving the boundary line means that the boundary line for dividing the image is moved up and down in the range from 0 on the Y axis to the height of the original image.

  Further, the average value of the extracted data is calculated, and the difference is obtained. In this way, the boundary line is sequentially moved to find the line where the difference between the average values of the gradation values in the two coordinate ranges is maximized, and the boundary line is determined.

  The coordinate value of the boundary line that divides the original image data into two is used as coordinate range information.

  Specifically, the coordinate range information when the boundary line is the eighth line in the original image data having the width of 50 and the height of 20 is (x, y) notation and (0, 0) (50, 8) is a diagonal line. And (0, 9) (50, 20) form a diagonal area. The coordinate range information is calculated for each of the RGB color components and stored in the coordinate range information storage memory 308.

  The division point information extraction unit 101 extracts division point information for each coordinate range extracted by the coordinate range information extraction unit 307. Thereafter, the same processing as in the first embodiment is performed to generate display image data. The generated image is displayed on the image display unit 106.

  As described above, according to the present embodiment, it is possible to improve display quality by assigning gradations to necessary areas while performing memory reduction by color reduction processing.

Incidentally, according to this embodiment, the original image data, color-reduced image data, the display image data is set to the RGB color components, it is also applicable to the other components of the luminance component and color difference components, such as YC _b C _r .

  Further, according to the present embodiment, as a coordinate range information, a rectangular area in the original image data is set as a range specified by the upper left coordinate value and the lower right coordinate value. Other methods may be used as long as the rectangular area can be specified, such as a range specified by the height and a range specified by the upper right coordinate value and the lower left coordinate value.

  Further, according to the present embodiment, the coordinate range calculation method can be applied not only to rows but also to columns, and a plurality of boundary rows or columns may be defined.

  Further, according to the present embodiment, the maximum change amount of the average value is used for the coordinate range information extraction method, but other methods such as a fixed value may be used.

(Embodiment 4)
The image display apparatus in this embodiment will be described.

  FIG. 11 is a block diagram of an image display apparatus according to the fourth embodiment.

  The image display device 4 includes an effective range selection unit 407 in the image display device 2.

  The effective range selection unit 407 selects the effective range of the maximum resolution range information from either the range of the maximum resolution range information, the outside of the range, or both, and assigns gradation values.

  Here, the effective range of the maximum resolution range information is defined as a range to which gradation values are assigned at the time of color reduction, within the maximum resolution range information is defined as the range of width information including vertices, and out of range is other than the above It is defined as the range.

  Hereinafter, a specific operation of the image display apparatus in the present embodiment will be described.

  In the effective range selection unit 407, the effective range is selected by a user's selection operation either within the range of the maximum resolution range information extracted by the maximum resolution range information extraction unit 201, outside the range, or both.

  The maximum resolution range information extraction unit 201 uses the method selected by the effective range selection unit 407 to extract maximum resolution range information including vertex information and width information. Thereafter, the same processing as in the second embodiment is performed to generate display image data. The generated image is displayed on the image display unit 206.

  As described above, according to the present embodiment, it is possible to effectively reduce the memory by performing the color reduction process and to assign the gradation only to the necessary area, thereby effectively assigning the gradation more effectively. Display quality can be improved.

  In each of the above embodiments, each process (each function) may be realized by centralized processing by a single device (system), or by distributed processing by a plurality of devices. May be.

  The present invention is not limited to the above-described embodiments, and various modifications are possible, and it goes without saying that these are also included in the scope of the present invention.

  As described above, the image display device according to the present invention has an effect of improving display quality as memory is reduced, and is useful as an electronic apparatus having an image display device such as a television, a mobile phone, or a personal computer. It is.

Block diagram of an image display device according to Embodiment 1 Conceptual diagram of dividing point extraction processing by the dividing point information extraction unit Conceptual diagram of color reduction processing using division points of the pseudo gradation processing unit Conceptual diagram of display image data generation processing from subtractive color image data using division points of same gradation correction unit Block diagram of an image display apparatus according to Embodiment 2 Conceptual diagram of maximum resolution range extraction processing of the same division point information extraction unit Conceptual diagram of color reduction processing using the maximum resolution range of the pseudo gradation processing unit Conceptual diagram of display image data generation processing from subtractive color image data using the maximum resolution range of the same gradation correction unit Block diagram of an image display apparatus according to Embodiment 3 Conceptual diagram of the coordinate range extraction process of the coordinate range information extraction unit Block diagram of an image display apparatus according to Embodiment 4 Block diagram of a conventional image display device The figure which shows the color reduction result by the conventional color reduction processing

Explanation of symbols

101 division point information extraction unit 102 division point information storage memory 103, 203 pseudo gradation processing unit 104, 204 frame buffer 105, 205 gradation correction unit 106, 206 image display unit 201 maximum resolution range information extraction unit 202 maximum resolution range information Storage memory 307 Coordinate range information extraction unit 308 Coordinate range information storage memory 407 Effective range selection unit

Claims (5)

Point information extraction means for receiving, as input, original image data in which each color component is expressed by at least 2 bits, and extracting point information for changing the gradation width with respect to the original image data;
Point information storage means for storing the point information;
A color reduction means for reducing the original image data into reduced color image data using the point information;
Reduced color image data storage means for storing the reduced color image data;
Display image data generating means for generating display image data from the point information and the color-reduced image data;
Image display means for displaying the display image data generated by the display image data generation means;
An image display device comprising:   2. The image display device according to claim 1, wherein the color reduction means performs color reduction so that the gradation widths are equal in a range where the gradation value is large and a small range around the point.   The color reduction means uses the point information as maximum resolution range information composed of vertex information and width information, and performs color reduction so that the gradation widths are equal within and outside the range of the maximum resolution range information. The image display device according to claim 1.   The image display device according to claim 1, wherein the point information extraction unit extracts point information for each of coordinate range information including a plurality of coordinate ranges with respect to the original image data.   4. The image display according to claim 3, wherein an effective range of the maximum resolution range information is selected from either the range of the maximum resolution range information, the range outside the range, or both, and the gradation value is assigned. apparatus.