JP2002016943A - Apparatus and method for displaying image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an apparatus for displaying an image capable of forming pallet data without using a color image memory and a histogram memory, reducing a calculating amount and conducting a natural image display. SOLUTION: This apparatus for displaying an image comprises a decoder 12 for expanding compression data and extracting a DC component of a DCT coefficient, a pallet data forming unit 13 for selecting a display pallet color from the extracted DC component, a color quantizer 4 for approximating the color image of an output of the decoder to a selected pallet color and converting the image into a color code given to the selected pallet color, a display memory 5 for holding the color image converted into the color code, a lookup table 6 for converting the color image held by the display memory into color data for a display driver, a display device 8 for displaying the color image, and a display driver 7 for controlling the display device according to the converted color data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an image display device and an image display method for performing color reduction processing in a device such as a portable terminal device having limited computational resources.

[0002]

2. Description of the Related Art In recent years, terminal devices for displaying images have rapidly become widespread. Such terminal devices often limit the number of colors that can be displayed to about 256 colors in order to keep the cost of the device low, thereby saving memory for display. Despite such limitations, the display capability is sufficient for applications such as documents and tables. However, when displaying a natural image such as a photograph, an image represented by about 24 bits is represented by 8 bits. It is necessary to perform a color reduction process for expression, and the image quality is greatly affected by the color reduction method. Therefore, there is an increasing demand for realizing high image quality by minimizing the calculation amount and the memory capacity used. As one of effective methods for color reduction, there is an adaptive palette method for selecting and displaying necessary 256 colors from tens of thousands of colors. Hereinafter, a conventional image display device will be described.

FIG. 7 is a block diagram showing a conventional image display device.

In FIG. 7, reference numeral 2 denotes a decoder for decoding compressed data 1 using DCT, and reference numeral 3 denotes an image memory for recording full-color data (color image data) output from the decoder 2 in full color. The full color memory 4 is a color quantizer that approximates full color data output from the decoder 2 with a palette color given from a palette data generator 11 described later. The color quantizer 4 converts the full-color data output from the decoder 2 into a color code represented by an 8-bit code by approximating the color data with the above-mentioned palette color. Reference numeral 5 denotes a display memory for storing a color code output from the color quantizer 4; 6, a color conversion table as a lookup table for converting the color code read from the display memory 5 into color data; A display driver for controlling a display device 8 described later in accordance with the color data output from the color conversion table 7, 8 a display device for displaying an image, 9 a histogram based on the full color data output from the decoder 2 A histogram creator 10 for storing a histogram created by the histogram creator 9; and 11, a pallet color used for displaying a color image based on the histogram created on the histogram memory 10. , A pallet data generator for generating pallet data p.

The operation of the thus configured image display device will be described with reference to FIG. FIG. 8 is a flowchart showing the operation of the image display device of FIG.

In FIG. 8, first, the decoder 2
Calculates the color data of each pixel by variable length decoding, inverse quantization and inverse DCT, and stores the obtained color image data in the full color memory 3 (S41). Next, the histogram creator 9 includes an image memory (full color memory)
Then, a color histogram is created based on the color data stored in No. 3 (S42), and the result is stored in the histogram memory 10. Next, the palette data generator 11 selects a palette color to be used for displaying a color image based on the histogram read from the histogram memory 10, and generates palette data p (S43). Next, the color quantizer 4 approximates (quantizes) the color of each pixel using the palette data p from the palette data generator 11 (S4).
4) The converted color is converted into a symbol (color code) and written into the display memory 5 (S45). Next, the color conversion table 6 performs conversion from symbols to color data (S4).
6) The display driver 8 drives the display device 8 to display an image (S47).

In the above-described conventional image display device, when selecting a color to be used, it is necessary to once develop the colors of the pixels of the entire image in the full-color memory 3 by inverse DCT conversion. Is stored in the memory 3. Furthermore, a huge amount of calculation is required to create a histogram from the color data,
An additional memory (histogram memory) 10 is required. This causes an increase in cost due to an enormous memory capacity and an increase in power consumption due to calculations for creating a histogram when an image is displayed in limited calculation resources such as a portable terminal device.

[0008]

As described above, the above-mentioned conventional image display apparatus has a problem that an increase in cost due to an enormous memory capacity and an increase in power consumption due to an operation for generating a histogram occur. Was.

In this image display device, by selecting a color at the stage of DCT coefficient and selecting a color for the conversion table in advance, color information of all pixels is prepared in advance without being developed on the memory. The color can be converted to symbols sequentially by approximating the color, so that palette data can be created without using a memory for storing a full-color image and a memory for creating a histogram, and further, a histogram for the entire image is created. By not performing the processing, it is required that the amount of calculation can be reduced, the power consumption can be reduced, and a more natural image can be displayed.

According to the present invention, in order to satisfy this demand, palette data can be created without using a memory for storing a full-color image and a memory for creating a histogram, and a process for creating a histogram of the entire image. Image display device that can reduce the amount of computation by not performing the processing, can reduce power consumption, and can perform more natural image display, and a memory for storing a full-color image and a memory for creating a histogram By reducing the amount of calculation by creating palette data without using
It is an object of the present invention to provide an image display method for reducing power consumption and displaying a more natural image.

[0011]

According to the present invention, there is provided an image display apparatus comprising: a decoder for expanding compressed data using DCT and extracting a DC component of a DCT coefficient; A palette data generator for selecting from the DC components from which the palette color to be extracted is extracted, and a color image output from the decoder which approximates the selected palette color and converts the color code given to the selected palette color to the selected color. A color quantizer for conversion, a display memory for holding a color image converted to a color code, a look-up table for converting the color image held in the display memory to color data for a display driver, and a display of a color image And a display driver that controls the display device according to the converted color data. It has the structure.

Thus, pallet data can be created without using a memory for storing a full-color image and a memory for creating a histogram, and the amount of computation can be reduced by eliminating the process of creating a histogram of the entire image. And an image display device capable of reducing power consumption and performing more natural image display can be obtained.

In order to solve the above-mentioned problems, an image forming method according to the present invention comprises an extracting step of extracting a DC component of a DCT coefficient from compressed data based on DCT, and a palette color selecting step of selecting the extracted DC component as a palette color. A decoding step of decoding the compressed data by inverse DCT to generate a color image; a color quantization step of approximating a color of a pixel of the generated color image with a selected palette color; A memory storage step of sequentially storing colors as color codes in a display memory;
A repetition step of repeating a decoding step, a color quantization step, and a memory storage step for all pixels of a color image; a color data conversion step of reading a stored color code from a display memory and converting the color code into color data; An image display step of displaying an image by controlling a display device based on color data.

Thus, palette data can be created without using a memory for storing a full-color image and a memory for creating a histogram, and the amount of calculation can be reduced by not performing processing for creating a histogram of the entire image. Thus, an image display method for reducing power consumption and displaying images more naturally can be obtained.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to a first aspect of the present invention includes a decoder for expanding compressed data using DCT and extracting a DC component of a DCT coefficient, and a palette color used for display. A palette data generator for selecting from the DC components from which the color has been extracted, and a color for approximating the color image output from the decoder to the selected palette color and converting the selected palette color into a given color code. A quantizer, a display memory for holding a color image converted into a color code, a look-up table for converting the color image held in the display memory into color data for a display driver, and a display device for displaying the color image And a display driver for controlling a display device according to the converted color data. A.

With this configuration, the palette color is selected and the palette data is created before the compressed image data (compressed data) is expanded, and the expanded full-color data is sequentially expanded without being expanded on the image memory. Since it can be written directly to the display memory, approximating the color,
This has the effect that the image memory for storing color image data and the histogram memory for storing histograms for creating palette data can be deleted. In addition, by selecting colors for display from the DC component of the decoder output, the calculation for selecting colors can be greatly reduced, and power consumption, which is extremely important in portable terminal devices, is reduced. Has the effect of being able to

According to a second aspect of the present invention, there is provided an image display method comprising:
Extracting a DC component of a DCT coefficient from compressed data based on, a palette color selecting step of selecting the extracted DC component as a palette color, and a decoding step of decoding the compressed data by inverse DCT to generate a color image A color quantization step of approximating the color of the pixel of the generated color image with the selected palette color; a memory storing step of sequentially storing the color of the pixel of the approximated color image as a color code in a display memory; A repetition step of repeating a decoding step, a color quantization step, and a memory storage step for all pixels, a color data conversion step of reading a stored color code from a display memory and converting it into color data, An image display step of controlling the display device to display an image. In which it was decided to.

With this configuration, the palette color is selected and the palette data is created before the compressed image data (compressed data) is expanded, and the expanded full-color data is sequentially expanded without being expanded on the image memory. Since it can be written directly to the display memory, approximating the color,
This has the effect that the image memory for storing color image data and the histogram memory for storing histograms for creating palette data can be deleted. Further, by selecting colors for display from the extracted DC components, it is possible to greatly reduce the calculation for selecting colors, and to reduce power consumption, which is extremely important in portable terminal devices and the like. Has the effect of being able to.

According to a third aspect of the present invention, in the image display method of the second aspect, in the palette color selecting step, the number of DC components is larger than the number of colors that can be selected as palette colors. In this case, the colors are selected in order from the DC component of the block located at the center of the color image,
The selection is terminated when the number of selectable colors is reached.

With this configuration, it is possible to define a more effective palette suitable for a portrait of a person while simplifying selection of colors to be used.

According to a fourth aspect of the present invention, in the image display method of the second aspect, in the palette color selecting step, the number of DC components is larger than the number of colors that can be selected as palette colors. In this case, the colors are sequentially selected from the DC components of the block around one or more arbitrary positions of the color image, and the selection is terminated when the number of selectable colors is reached.

This configuration has the effect of simplifying the selection of colors to be used and defining an effective palette when displaying a photograph of a plurality of persons or a photograph of a person and an object.

According to a fifth aspect of the present invention, there is provided the image display method according to any one of the second to fourth aspects, wherein:
In the palette color selection step, if the number of DC components is larger than the number of colors that can be selected as a palette color, if a similar color exists in a neighboring block, it is selected as a different color, and a similar color is selected. Are located in distant blocks, the same color is selected.

This configuration has the effect of suppressing the phenomenon in which the line of changing color is emphasized and creating an effective palette for a natural image such as a photograph.

According to a sixth aspect of the present invention, there is provided an image display method as set forth in any one of the second to fourth aspects.
In the palette color selection step, if the number of DC components is larger than the number of colors that can be selected as a palette color, if there is a similar color in a block that is longer than the set distance, it is determined as a different color. If there is a similar color in a block that is closer to the selected distance than the set distance, the block is selected as the same color.

This configuration has the effect of creating a palette suitable for an image such as an illustration with a clear change in color, ignoring fine changes in neighboring pixels.

According to a seventh aspect of the present invention, there is provided the image display device according to the first aspect, further comprising a discriminating unit for discriminating whether the image is a natural image or a composite image based on an identifier of an input color image. When the color image is determined to be a natural image, image display is performed by the image display method described in claim 4, and when the color image is determined to be a composite image, the image described in claim 5 is displayed. The image display is performed by the display method.

With this configuration, a palette suitable for an image having a smooth change in color such as a photograph or CG and an image such as a line drawing or a poster occupying a wide area can be created. It has the effect of obtaining a high image quality.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described with reference to FIG.

(Embodiment 1) FIG. 1 is a block diagram showing an image display apparatus according to Embodiment 1 of the present invention.

In FIG. 1, the color quantizer 4, the display memory 5, the look-up table 6, the display driver 7, and the display device 8 are the same as those shown in FIG. Reference numeral 12 denotes a decoder which decodes the input compressed data 1 and outputs decoded full-color data (color image data) and extracts a DC component. Reference numeral 13 denotes a decoder which receives the DC component output from the decoder 12. Pallet data generator. Palette data (data indicating a palette color) created by the palette data creating unit 13 is input to the color quantizer 4 and the lookup table 6.

The functions and the like of the image display device configured as described above will be described.

The compressed data 1 is obtained by subjecting an original image to DCT conversion or the like. In JPEG which is a standard method for compressing a still image, this DCT conversion is performed for each 8 × 8 pixel block, and further DCT conversion is performed. Quantization is performed centering on the high-frequency components obtained by the above, and the data is further subjected to variable-length coding to realize compression of image data. The decoder 12 performs variable length decoding and inverse quantization on the compressed data 1 to extract DCT coefficients. The decoder 12 sequentially extracts only the DC component (DC component) a of the DCT coefficients recorded at the head of the block data among the DCT coefficients, performs an inverse DCT transform, and performs actual DCT conversion from the DCT coefficients. The color image data (full color data) v is generated. Pallet data generator 1
3 selects, from the input DC component a, different colors as many as the number designated for the device, and sets palette data p
Output as The color quantizer 3 quantizes the colors of the pixels of the color image (full color image) v output from the decoder 12 with the palette data p using an existing algorithm, and performs color quantification using a color code indicating the assigned color. The colors of the image v are sequentially expressed and written to the display memory 5. The display memory 5 has a capacity to store all the data (color code data) expressing the pixels of the entire color image v with color codes. The look-up table 6 converts the color code read from the display memory 5 into color data expressed in full color. Specifically, a color code is used as an address, and the selected full-color color data is stored in an entry of a memory specified by the address, and the selected color data is output by inputting the address. Further, the display driver 7 generates a voltage for controlling the display device 8 according to the color data. The display device 8 displays a color image by causing each color component to emit color according to the voltage given from the display driver 7.

The operation of the image display device configured as described above will be described with reference to FIG. FIG. 2 is a flowchart showing the operation of the image display device according to the first embodiment of the present invention.

First, the decoder 12 to which the compressed data 1 is input in block units performs variable length decoding and inverse quantization on the compressed data 1 to extract the DC component a of the DCT coefficient (S1, Extraction step). The palette data generator 13 selects a palette color to be used in the actual display based on the DC component a extracted by the decoder 12 (palette color selection step), and as a palette data, the color quantizer 4
Is registered in the lookup table 6 (S2). next,
The decoder 12 performs an inverse DCT transform (decoding) on the pixels of each block to calculate color data of the pixels of the color image (S3, decoding step). Next, the color quantizer 4
Performs quantization (approximation) of the color data of the color image v using the palette color selected by the palette data generator 13 (color quantization step), and converts the quantized color into a color code (S4). Then, the color code is written into the display memory 5 (S5, memory storage step). Step S3 to step S for all pixels in all blocks
5 is repeated (repeated step). Next, the look-up table 7 reads the color code stored from the display memory 5, inputs the color code as an address of the look-up table, and creates color data for display (S7, color data conversion step). . The display driver 7 converts the color data created by the look-up table 6 into a voltage, drives the display device 8, and the display device 8 displays the color image subjected to the color reduction processing (S8, image display step).

As described above, according to the present embodiment, DC
By selecting a color (palette color) to be used for the palette from the DC component a of the T coefficient, there is no need to create a histogram for creating palette data,
The amount of calculation can be significantly reduced, and power consumption can be reduced, and at the same time, the amount of memory required for the histogram can be significantly reduced. Also, by creating a palette color first, and then sequentially approximating the color image data v, which is the output of the inverse DCT transform, and writing it to the display memory 5,
It is not necessary to develop full-color data of the entire color image on the memory, so that a huge work area can be deleted.

(Embodiment 2) The configuration of an image display apparatus according to Embodiment 2 of the present invention is the same as that of FIG. 1, and a description thereof will be omitted. The present embodiment relates to a method of selecting colors by palette data generator 13 in the first embodiment. In the present embodiment, the pallet data generator 1
3 has three operation modes. The three operation modes are a center priority mode, a neighbor priority mode, and a neighbor same color mode.

The operation mode of the image display apparatus thus configured will be described with reference to FIGS. FIG. 3 shows the pallet data generator 13 in the central priority mode.
FIG. 4 is an explanatory diagram showing the order of color extraction in the center priority mode, FIG. 5 is a flowchart showing the operation of the pallet data generator 13 in the neighborhood priority mode, and FIG. 5 is a flowchart showing the operation of the pallet data generator 13 in FIG.

First, the operation in the center priority mode will be described with reference to FIGS.

In FIG. 3, first, the size of an image is input (S11), a block existing near the center of the image is calculated based on the image size (S12), and a search start position is determined (S13). . Next, the DC component a of the block
Is selected as the pallet data p (S14). Next, it is determined whether or not the pallet data has reached the number of pallets (S15). If it is determined that the pallet data has not yet reached the pallet number, the order shown in FIG.
To search for blocks of the image. When it is determined that the number of palettes has been reached, the selection of palette colors is completed.

Next, the neighborhood priority mode will be described with reference to FIG.

In FIG. 5, first, a search mask for determining how similar colors are regarded as the same color is set (S21). Next, a predetermined order (for example, 1
From left to right the block on the line, and on the second line ...
The DC component a is extracted from the blocks constituting the image according to (the order of the last row) (S22). Next, it is determined whether a color similar to the DC component a has already been registered as palette data using the search mask (S2).
3). If it is determined that the DC component a has already been registered, the process jumps to step S26 to register the DC component a as the same color as the similar color, and if it is determined that the DC component a has not been registered, the process proceeds to step S24. In step S24, the distance (Euclidean distance) on the color image between the block in which the registered color has been selected and the block in which the DC component a has been selected is compared. If the distance is shorter than the threshold value, the process proceeds to step S24. The process jumps to S25, and if far, jumps to step S27. In step S25, it is determined whether or not the registered color and the DC component a completely match without the inspection mask. If it is determined that they completely match, step S2
If it is determined that they do not match, registration is made as pallet data in step S26. In step S27,
It is determined whether the search has been completed for all blocks constituting the image, and if not, step S22
Then, when all the blocks have been searched, the pallet data creation ends.

Next, the neighboring same-color mode will be described with reference to FIG.

In FIG. 6, first, a search mask for determining how similar colors are regarded as the same color is set (S31). Next, a predetermined order (for example, 1
From left to right the block on the line, and on the second line ...
The DC component a is extracted from the blocks constituting the image according to (the order of the last row) (S32). Next, it is determined whether a color similar to the DC component a has already been registered as palette data using the search mask (S3).
3). If it is determined that the DC component a has already been registered, the process jumps to step S36 to register the DC component a as the same color as the similar color. If it is determined that the DC component a has not been registered, the process proceeds to step S34. In step S34, the distance (Euclidean distance) on the color image between the block in which the registered color is selected and the block in which the DC component a is selected is compared, and if the distance is longer than the threshold value, The process jumps to S35, and if close, jumps to step S37. In step S35, it is determined whether or not the registered color and the DC component a completely match without the inspection mask. If it is determined that they completely match, step S3
7, if it is determined that they do not match, it is registered as pallet data in step S36. In step S37,
It is determined whether or not the search has been completed for all blocks constituting the image.
Then, when all the blocks have been searched, the pallet data creation ends.

Further, the present embodiment shows means for selecting a mode of the pallet data generator 13 in the second embodiment.

In the image display device thus configured, the attribute value of compressed data (for example, the extension of the file name)
Is checked, and the operation mode is determined. Specifically, if the file name is image. jpg, neighbor priority mode, i
image. jsg, neighbor same color mode, imag
e. If it is "jpp", the central priority mode is selected. The information indicating the mode determined here is the pallet data generator 1
3, the image is displayed by the procedure corresponding to each mode in the second embodiment according to the information indicating the mode.

As described above, according to the present embodiment, when there is a point to be focused on the center of the image such as a portrait of a person's face, the center priority mode is selected, and the center of the image is selected. By preferentially selecting existing colors,
Even when a large area is represented by a similar color like a person's face, it is possible to represent a smooth color change of the face surface. Also, when displaying an image having a lot of smooth color changes such as a photograph or a three-dimensional CG, a neighborhood priority mode is selected, and similar colors are registered as palette data for neighboring blocks. By expressing subtle changes in the neighborhood, and treating similar colors as the same color when the distance is long, palette data can be saved. Furthermore, in an image where many planes of the same color exist, such as a line drawing or a poster, the neighboring same-color mode is selected, and similar colors are regarded as the same color for neighboring blocks, thereby reducing noise generated when encoding the image. It becomes possible to reduce. In this way, a more natural image can be generated.

[0048]

As described above, according to the image display apparatus of the first aspect of the present invention, a decoder for expanding compressed data using DCT and extracting a DC component of a DCT coefficient, and A palette data generator for selecting from the DC components from which the palette color to be used is extracted, and a color code given to the selected palette color while approximating the color image output from the decoder to the selected palette color A color quantizer that converts the color image into a color code, a display memory that stores the color image converted into the color code, a look-up table that converts the color image stored in the display memory into color data for the display driver, A display device for displaying, and a display driver for controlling the display device according to the converted color data. Before expanding the compressed image data (compressed data), the palette color is selected and the palette data is created, and the expanded full-color data is successively approximated to the palette color without being expanded on the image memory. Since the image data can be written directly to the display memory, the advantageous effect that the image memory for storing the color image data and the histogram memory for storing the histogram for creating the palette data can be eliminated is obtained. In addition, by selecting colors for display from the DC component of the decoder output, the calculation for selecting colors can be greatly reduced, and power consumption, which is extremely important in portable terminal devices, is reduced. This has the advantageous effect that it can be performed.

According to the image display method of the second aspect,
An extraction step of extracting DC components of DCT coefficients from DCT-based compressed data, a palette color selection step of selecting the extracted DC components as palette colors, and a decoding of decoding the compressed data by inverse DCT to generate a color image A color quantization step of approximating the color of the pixel of the generated color image with the selected palette color; a memory storage step of sequentially storing the color of the pixel of the approximated color image as a color code in a display memory; An iterative step of repeating a decoding step, a color quantization step, and a memory storage step for all the pixels of the image data; a color data conversion step of reading a stored color code from a display memory and converting the color code into color data; Image display step to control the display device and display the image By selecting a palette color before expanding the compressed image data (compressed data), the palette data is created, and the expanded full-color data is sequentially expanded without being expanded on the image memory. Can be directly written into the display memory, which has an advantageous effect that the image memory for storing color image data and the histogram memory for storing a histogram for creating palette data can be eliminated. . In addition, DC which extracted the color for display
By selecting from the components, the operation for selecting the color can be significantly reduced, and the advantageous effect that power consumption, which is extremely important in a portable terminal device or the like, can be reduced can be obtained.

According to the image display method of the third aspect,
3. The image display method according to claim 2, wherein, in the palette color selecting step, if the number of DC components is larger than the number of colors that can be selected as palette colors, the DC of the block located at the center of the color image is determined. By selecting colors in order from the components and ending selection when the number of selectable colors is reached, it is possible to define a more effective palette suitable for portraits of people etc. while simplifying selection of colors to use The advantageous effect described above can be obtained.

According to the image display method of the fourth aspect,
3. The image display method according to claim 2, wherein, in the palette color selecting step, when the number of DC components is larger than the number of colors that can be selected as palette colors, one or more arbitrary positions of the color image By selecting colors from the DC components of the block in order, and ending the selection when the number of selectable colors is reached, simplifying the selection of colors to be used, and simplifying the selection of a plurality of persons or persons and objects. An advantageous effect is obtained that an effective palette can be defined when displaying a photograph or the like in which an object is displayed.

According to the image display method of the fifth aspect,
In the image display method according to any one of claims 2 to 4, when the number of DC components is larger than the number of colors that can be selected as a palette color in the palette color selection step, a similar color is selected. By selecting a different color when it is in a neighboring block, and by selecting the same color when a similar color is in a distant block, it is possible to suppress the phenomenon that a line that changes color is emphasized, An advantageous effect is obtained that an effective palette for a natural image such as a photograph can be created.

According to the image display method of the sixth aspect,
5. The image display method according to claim 2, wherein, in the palette color selecting step, if the number of DC components is larger than the number of colors that can be selected as palette colors, the set distance is set. If there is a similar color in a block farther away than the set distance, it is selected as a different color, and if there is a similar color in a block closer than the set distance, it is selected as the same color, so that the neighboring pixels are finer. An advantageous effect is obtained in that a palette suitable for an image such as an illustration with a clear change in color, ignoring the change, can be created.

According to the image display device of the seventh aspect,
2. The image display device according to claim 1, further comprising a determination unit configured to determine whether the input image is a natural image or a composite image based on an identifier of the input color image, wherein the determination unit determines that the color image is a natural image. Image display is performed by the image display method described in claim 4, and when a color image is determined to be a composite image, image display is performed by the image display method described in claim 5, so that a photograph, CG, or the like is displayed. This makes it possible to create palettes suitable for images with smooth color changes such as, and images where the same color occupies a large area, such as line drawings and posters. The effect is obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an image display device according to Embodiments 1 and 2 of the present invention.

FIG. 2 is a flowchart showing an operation of the image display device according to the first embodiment of the present invention;

FIG. 3 is a flowchart showing the operation of the pallet data generator in the center priority mode.

FIG. 4 is an explanatory diagram showing the order of color extraction in the center priority mode.

FIG. 5 is a flowchart showing the operation of the pallet data generator in the neighborhood priority mode.

FIG. 6 is a flowchart showing the operation of the palette data generator in the same-color neighborhood mode.

FIG. 7 is a block diagram showing a conventional image display device.

FIG. 8 is a flowchart showing the operation of the image display device of FIG. 7;

[Explanation of symbols]

 4 Color quantizer 5 Display memory 6 Lookup table 7 Display driver 8 Display device 12 Decoder 13 Pallet data generator

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Claims (7)

[Claims] 1. A decoder for expanding compressed data using DCT and extracting a DC component of a DCT coefficient, and a palette data generator for selecting a palette color to be used for display from the extracted DC components. A color quantizer for approximating a color image output from the decoder to the selected palette color and converting the selected palette color to a given color code; and a color converted to the color code. A display memory for holding an image, a look-up table for converting a color image held in the display memory into color data for a display driver,
An image display device comprising: a display device that displays a color image; and a display driver that controls the display device according to the converted color data. 2. An extraction step of extracting a DC component of a DCT coefficient from compressed data based on the DCT;
A palette color selecting step of selecting the C component as a palette color, a decoding step of decoding the compressed data by inverse DCT to generate a color image, and a step of setting a pixel color of the generated color image by the selected palette color. An approximate color quantization step, a memory storage step of sequentially storing the colors of the pixels of the approximated color image as a color code in a display memory, the decoding step and the color quantization step for all the pixels of the color image A color data conversion step of reading the stored color code from the display memory and converting it into color data, and controlling a display device with the converted color data to display an image. An image display step. 3. In the palette color selecting step, if the number of DC components is larger than the number of colors that can be selected as palette colors, the DC components of the block located at the center of the color image are sequentially colored. 3. The image display method according to claim 2, wherein the selection is terminated, and the selection is terminated when the number of selectable colors is reached. 4. In the palette color selecting step, when the number of DC components is larger than the number of colors that can be selected as palette colors, one or more arbitrary positions of the color image are sequentially centered. 3. The image display method according to claim 2, wherein a color is selected from the DC components of the block, and the selection is terminated when the number of selectable colors is reached. 5. In the palette color selecting step, when the number of DC components is larger than the number of colors that can be selected as a palette color, if a similar color exists in a neighboring block, it is determined as a different color. 5. The image display method according to claim 2, wherein, when a similar color is selected in a distant block, the selected color is selected as the same color. 6. In the palette color selecting step, if the number of DC components is larger than the number of colors that can be selected as palette colors, there are similar colors in blocks farther than a set distance. If you choose different color,
5. The image display method according to claim 2, wherein when a similar color exists in a block closer than the set distance, the color is selected as the same color. 6. 7. A system according to claim 4, further comprising a discriminating means for discriminating whether the input image is a natural image or a composite image based on an identifier of the input color image. The image display is performed by the described image display method, and when it is determined that the color image is a composite image, the image display is performed by the image display method according to claim 5. Image display device.