Coding apparatus, decoding apparatus, coding method, decoding method, amd computer-readable recording medium for executing the methods

A coding apparatus which compresses a color image including a plurality of components as color components that form a color image to generate code information, said apparatus comprising:

• a separation unit which separates information for each component into a DC component and AC components in each predetermined block;
• a transformation unit which transforms the AC components separated by said separation unit to a lightness signal and color signals to obtain an AC lightness signal and AC color signals;
• and
• a quantization unit which performs quantization on the AC lightness signal and/or the AC color signals obtained by said transformation unit,
• wherein when the AC lightness signal and AC color signals are quantized, said quantization unit performs quantization on a ratio between the AC lightness signal and each of the AC color signals.

A coding apparatus which compresses a color image including a plurality of components as color components that form a color image to generate code information, said apparatus comprising:

• a separation unit which separates information for each component into a DC component and AC components in each predetermined block;
• an AC component quantization unit which performs quantization on the AC components separated by said separation unit;
• a first transformation unit which transforms the DC component separated by said separation unit to a lightness signal and color signals to obtain a DC lightness signal and DC color signals;
• a second transformation unit which transforms the AC components quantized by said first quantization unit to a lightness signal and color signals to obtain an AC lightness signal and AC color signals;
• and
• a quantization unit which performs quantization on the AC lightness signal and/or the AC color signals transformed by said second transformation unit.

A coding apparatus for a color image which compresses a color image including a plurality of components as color components that form a color image, said apparatus comprising:

• a separation unit which separates information for each component into a DC component and AC components in each predetermined block;
• a transformation unit which transforms the DC component separated by said separation unit to a lightness signal and color signals to obtain a DC lightness signal and DC color signals;
• and
• a quantization unit which performs quantization on the AC components separated by said separation unit,
• wherein said quantization unit performs vector quantization on a specific color that has an edge with a largest value of the AC components, and performs quantization on a ratio between a component of another color and a vector of the specific color.

A coding apparatus for compressing a color image including a plurality of color components that form the color image, to generate code information, said apparatus comprising:

• a transformation unit configured to perform a block truncation coding transformation on image data for each color component in each predetermined block to produce average density data, gradation width index data, and quantized value data for each color component;
• a color conversion unit configured to perform color conversion on the average density data, the gradation width index data, and the quantized value data for each color component by correlating the color components so as to bias the converted average density data, the converted gradation width index data, and the converted quantized value data;
• and
• a quantization unit configured to perform quantization on the converted average density data, the converted gradation width index data, and the converted quantized value data to generate said code information.

A coding apparatus for a color image which compresses a color image including a plurality of components as color components that form a color image to generate code information, said apparatus comprising:

• a first transformation unit which transforms information for each component by using a one-dimensional or two-dimensional position correlation of an image in each predetermined block so that bias is generated in the amount of information;
• a second transformation unit which transforms the information transformed by said first transformation unit to obtain a lightness signal and color signals;
• a region determination unit which determines any region of the image in each of said predetermined blocks;
• a quantization unit which performs different quantization for each region on the coefficients obtained through transformation by said first transformation unit and/or said second transformation unit based on the result of determination in said region determination unit;
• and
• a flag information creation unit which creates flag information to identify the region determined by said region determination unit.

A coding apparatus which compresses a color image including a plurality of components as color components that form a color image to generate code information, said apparatus comprising:

• a separation unit which separates information for each component into a DC component and AC components in each predetermined block;
• a first quantization unit which performs quantization on the AC components separated by said separation unit;
• a transformation unit which transforms the AC components quantized by said first quantization unit to a lightness signal and color signals to obtain an AC lightness signal and AC color signals;
• a region determination unit which determines which region of a plurality of regions said predetermined block belongs to based on the magnitude of at least one amplitude of the AC components, the AC lightness signal, and the AC color signals in each of said predetermined blocks;
• a second quantization unit which performs different quantization for each region on the AC lightness signal and/or the AC color signals based on the result of determination in said region determination unit;
• and
• a flag information creation unit which creates flag information to identify the region determined by said region determination unit.

A decoding apparatus which decodes code information for a color image including a plurality of components as color components that form a color image, said apparatus comprising:

• an inverse quantization unit which performs inverse quantization on the code information to restore an AC lightness signal, AC color signals, a DC lightness signal, and DC color signals;
• a first inverse color conversion unit which performs inverse color conversion on the AC lightness signal and the AC color signals to restore an AC signal;
• a second inverse color conversion unit which performs inverse color conversion on the DC lightness signal and the DC color signals to restore a DC signal;
• an AC inverse quantization unit which performs inverse quantization on the AC signal restored in said first inverse color conversion unit;
• and
• a position-correlation inverse transformation unit which performs inverse transformation of position correlation on the DC signal restored in said second inverse color conversion unit and the AC signal inverse-quantized in said AC inverse quantization unit to restore each component of said color image.

A decoding apparatus which decodes code information for a color image including a plurality of components as color components that form a color image, said apparatus comprising:

• an inverse quantization unit which performs inverse quantization on the code information to restore an AC lightness signal, an AC color signal, and a DC signal;
• a first inverse color conversion unit which performs inverse color conversion on the AC lightness signal and the AC color signals to restore an AC signal;
• an AC inverse quantization unit which performs inverse quantization on the AC signal restored in said first inverse color conversion unit;
• and
• a position-correlation inverse transformation unit which performs inverse transformation of position correlation on the DC signal and the AC signal inverse-quantized in said AC inverse quantization unit to restore each component of said color image.

A decoding apparatus which decodes code information for a color image including a plurality of color components that form the color image, said apparatus comprising:

• an inverse quantization unit configured to perform inverse quantization on the code information to generate converted average density data, converted gradation width data, and converted quantized value data;
• an inverse color conversion unit configured to perform inverse color conversion on the converted average density data, the converted gradation width data, and the converted quantized value data to generate average density data, gradation width index data, and quantized value data for each color component;
• and
• an inverse block truncation coding unit which performs an inverse block truncation coding transformation on the quantized value data the average density data, and the gradation width index data to restore each color component of said color image.

A decoding apparatus which decodes code information for a color image including a plurality of components as color components that form a color image, said apparatus comprising:

• a region determination unit which determines any region to which code information belongs from flag information;
• an inverse quantization unit which performs different inverse quantization for each region on the code information for said predetermined block based on the result of determination in said region determination unit to restore a DC lightness signal, DC color signals, an AC lightness signal, and AC color signals;
• a first inverse color conversion unit which performs inverse color conversion on the AC lightness signal and the AC color signals to restore an AC signal;
• a second inverse color conversion unit which performs inverse color conversion on the DC lightness signal and the DC color signals to restore a DC signal;
• an AC inverse quantization unit which performs inverse quantization on the AC signal restored in said first inverse color conversion unit;
• and
• a position-correlation inverse transformation unit which performs inverse transformation of position correlation on the DC signal restored in said second inverse color conversion unit and the AC signal inverse-quantized in said AC inverse quantization unit to restore each component of said color image.

A decoding apparatus which decodes code information for a color image including a plurality of components as color components that form a color image, said apparatus comprising:

• a region determination unit which determines any region to which code information belongs from flag information;
• an inverse quantization unit which performs different inverse quantization for each region on the code information for said predetermined block based on the result of determination in said region determination unit to restore a DC signal, an AC lightness signal, and AC color signals;
• a first inverse color conversion unit which performs inverse color conversion on the AC lightness signal and the AC color signals to restore an AC signal;
• and
• a position-correlation inverse transformation unit which performs inverse transformation of position correlation on the DC signal restored in said inverse quantization unit and the AC signal restored in said first inverse color conversion unit to restore each component of said color image.

A coding method for compressing a color image including a plurality of components as color components that form a color image to generate code information, said method comprising:

• a first step of transforming information for each component by using a one-dimensional or two-dimensional position correlation of an image so that bias is generated in the amount of information;
• a second step of transforming the information transformed in said first step to obtain a lightness signal and color signals;
• and
• a third step of performing quantization on a plurality of coefficients obtained through transformation in said first step and/or said second step,
• wherein at least one of the coefficients that correspond to a slant edge of the color image is not transformed by the second step.

A coding method for compressing a color image including a plurality of components as color components that form a color image to generate code information, said method comprising:

• a first step of separating information for each of said components into a DC component and AC components in each predetermined block;
• a second step of transforming the separated AC components to a lightness signal and color signals to obtain an AC lightness signal and AC color signals;
• and
• a third step of performing quantization on the AC lightness signal and/or the AC color signals,
• wherein when the AC lightness signal and AC color signals are quantized, said quantization unit performs quantization on a ratio between the AC lightness signal and each of the AC color signals.

A coding method for compressing a color image including a plurality of components as color components that form a color image to generate code information, said method comprising:

• a first step of separating information for each of said components into a DC component and AC components in each predetermined block;
• a second step of performing quantization on the separated AC components;
• a third step of transforming the separated DC component to a lightness signal and color signals to obtain a DC lightness signal and DC color signals;
• a fourth step of transforming the quantized AC components to a lightness signal and color signals to obtain an AC lightness signal and AC color signals;
• and
• a fifth step of performing quantization on the transformed AC lightness signal and/or the AC color signals.

A coding method for compressing a color image including a plurality of color components that form the color image, to generate code information, said method comprising:

• a first step of separating information for each component into a DC component and AC components in each predetermined block;
• a second step of transforming the separated DC component into a lightness signal and color signals to obtain a DC lightness signal and DC color signals;
• and
• a third step of performing quantization on the separated AC components,
• wherein said first step includes performing a Haar wavelet transformation.

A coding method for compressing a color image including a plurality of color components that form the color image, to generate code information, said method comprising:

• a first step of performing a block truncation coding transformation on image data for each color component in each predetermined block to produce average density data, gradation width index data, and quantized value data for each color component;
• a second step of performing color conversion on the average density data the gradation width index data, and the quantized value data for each color component by correlating the color components so as to bias the converted average density data, the converted gradation width index data, and the converted quantized value data;
• and
• a third step of performing quantization on the converted average density data, the converted gradation width index data, and the converted quantized value data to generate said code information.

A coding method for compressing a color image including a plurality of components as color components that form a color image to generate code information, said method comprising:

• a first step of transforming information for each component by using a one-dimensional or two-dimensional position correlation of an image in each predetermined block so that bias is generated in the amount of information;
• a second step of transforming the information transformed in the first step to obtain a lightness signal and color signals;
• a third step of determining any region of the image in each of said predetermined blocks;
• a fourth step of performing different quantization for each region on the coefficients obtained through transformation in the first step and/or the second step based on the result of determination on said region;
• and
• a fifth step of creating flag information to identify the determined region.

A coding method for compressing a color image including a plurality of components as color components that form a color image to generate code information, said method comprising:

• a first step of separating information for each component into a DC component and AC components in each predetermined block;
• a second step of performing quantization on the separated AC components;
• a third step of transforming the quantized AC components to a lightness signal and color signals to obtain an AC lightness signal and AC color signals;
• a fourth step of determining which region of a plurality of regions said predetermined block belongs to based on the magnitude of at least one amplitude of the AC components, the AC lightness signal, and the AC color signals in each of said predetermined blocks;
• a fifth step of performing different quantization for each region on the AC lightness signal and/or the AC color signals based on the result of determination on said region;
• and
• a sixth step of creating flag information to identify the determined region.

A decoding method for decoding code information for a color image including a plurality of components as color components that form a color image, said method comprising:

• a first step of performing inverse quantization on the code information to restore an AC lightness signal, AC color signals, a DC lightness signal, and DC color signals;
• a second step of performing inverse color conversion on the AC lightness signal and the AC color signals to restore an AC signal;
• a third step of performing inverse color conversion on the DC lightness signal and the DC color signals to restore a DC signal;
• a fourth step of performing inverse quantization on the restored AC signal;
• and
• a fifth step of performing inverse transformation of position correlation on the restored DC signal and the inverse-quantized AC signal to restore each component of said color image.

A decoding method for decoding code information for a color image including a plurality of components as color components that form a color image, said method comprising:

• a first step of performing inverse quantization on code information to restore an AC lightness signal, an AC color signal, and a DC signal;
• a second step of performing inverse color conversion on the AC lightness signal and the AC color signals to restore an AC signal;
• a third step of performing inverse quantization on the restored AC signal;
• and
• a fourth step of performing inverse transformation of position correlation on the restored DC signal and the inverse-quantized AC signal to restore each component of said color image.

A decoding method for decoding code information for a color image including a plurality of color components that form the color image, said method comprising:

• a first step of performing inverse quantization on the code information to generate converted average density data, converted gradation width data, and converted quantized value data;
• a second step of performing inverse color conversion on the converted average density data, the converted gradation width data, and the converted quantized value data to generate average density data, gradation width index data, and quantized value data for each color component;
• and
• a third step of performing an inverse block truncation coding transformation on the quantized value data, the average density data, and the gradation width index data to restore each color component of said color image.

A decoding method for decoding code information for a color image including a plurality of components as color components that form a color image, said method comprising:

• a first step of determining any region to which code information belongs from flag information;
• a second step of performing different inverse quantization for each region on the code information for said predetermined block based on the result of determination on said region to restore a DC lightness signal, DC color signals, an AC lightness signal, and AC color signals;
• a third step of performing inverse color conversion on the AC lightness signal and the AC color signals to restore an AC signal;
• a fourth step of performing inverse color conversion on the DC lightness signal and the DC color signals to restore a DC signal;
• a fifth step of performing inverse quantization on the restored AC signal;
• and
• a sixth step of performing inverse transformation of position correlation on the inverse-quantized AC signal and the restored DC signal to restore each component of said color image.

A decoding method for decoding code information for a color image including a plurality of components as color components that form a color image, said method comprising:

• a first step of determining any region to which code information belongs from flag information;
• a second step of performing different inverse quantization for each region on the code information for said predetermined block based on the result of determination on said region to generate a DC signal, an AC lightness signal, and AC color signals;
• a third step of performing inverse color conversion on the AC lightness signal and the AC color signals to restore an AC signal;
• a fourth step of performing inverse quantization on the restored AC signal;
• and
• a fifth step of performing inverse transformation of position correlation on the restored DC signal and the inverse-quantized AC signal to restore each component of said color image.

A coding apparatus which compresses a color image including a plurality of components as color components that form a color image to generate code information, said apparatus comprising:

• a separation unit which separates information for each component into a DC component and AC components in each predetermined block;
• a transformation unit which transforms the AC components separated by said separation unit to a lightness signal and color signals to obtain an AC lightness signal and AC color signals;
• and
• a quantization unit which performs quantization on the AC lightness signal and/or the AC color signals obtained by said transformation unit,
• wherein said quantization unit sets a threshold value to a value larger than a median point of quantized values when vector quantization is performed.

A coding apparatus for a color image which compresses a color image including a plurality of color components that form the color image, said apparatus comprising:

• a separation unit configured to separate information for each component into a DC component and AC components in each predetermined block;
• a transformation unit configured to transform the DC component separated by said separation unit to a lightness signal and color signals to obtain a DC lightness signal and DC color signals;
• and
• a quantization unit configured to perform quantization on the AC components separated by said separation unit,
• wherein said separation unit is configured to perform a Haar wavelet transform.

A coding method for compressing a color image including a plurality of components as color components that form a color image to generate code information, said method comprising:

• a first step of separating information for each of said components into a DC component and AC components in each predetermined block;
• a second step of transforming the separated AC components to a lightness signal and color signals to obtain an AC lightness signal and AC color signals;
• and
• a third step of performing quantization on the AC lightness signal and/or the AC color signals,
• wherein said quantization unit sets a threshold value to a value larger than a median point of quantized values when vector quantization is performed.

A coding apparatus which compresses a color image including a plurality of components as color components that form a color image to generate code information, said apparatus comprising:

• a first transformation unit which transforms information for each component by using a one-dimensional or two-dimensional position correlation of an image so that bias is generated in the amount of information;
• a second transformation unit which transforms the information transformed by said first transformation unit to obtain a lightness signal and color signals;
• and
• a quantization unit which performs quantization on a plurality of coefficients obtained through transformation by said first transformation unit and/or said second transformation unit,
• wherein the first transformation unit associates a first amount of information with a first coefficient and associates a second amount of information less than the first amount of information with a second coefficient to generate the bias in the amount information, and
• wherein the first transformation unit divides the information for each of the plurality of components into DC information and AC information using the position correlation of the color image.