Method of an apparatus for compressing images data
AssigneeDainippon Screen Mfg. Co., Ltd.
InventorMasami Aragaki
Life of this patent
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Abstract
An image is conceptually divided into pixel blocks each having a plurality of pixels. RGB image data representing the image are converted into luminance data and color difference data in the NTSC form. Standard deviation values of these data are calculated in each pixel block and are compared with threshold values, so that the pixel blocks are classified into two types. The image data in the pixel blocks of respective types are compressed at different compression rates to obtain image data compressed.
Claims16
A method of compressing image data which represent an image in the form of an array of pixels for each color component, wherein said array of pixels are divided into pixel blocks each having a plurality of pixels, said method comprising the steps of:
- (a) obtaining luminance data representing luminance of said image for each pixel as a function of said image data;
- (b) obtaining color difference data representing differences between said image data of respective color components for each pixel;
- (c) obtaining a first statistic representing a standard deviation of said luminance data in each pixel block;
- (d) obtaining a second statistic representing a standard deviation of said color difference data in each pixel block;
- (e) comparing said first and second statistics with first and second threshold values, respectively, to classify respective pixel blocks into first and second type pixel blocks;
- and
- (f) compressing said image data of said first type pixel blocks at a first compression rate and compressing said image data of said second type pixel blocks at a second compression rate to thereby obtain compressed image data, wherein said first compression rate is different from said second compression rate.
An apparatus for compressing image data which represent an image in the form of an array of pixels for each color component, wherein said array of pixels are divided into pixel blocks each having a plurality of pixels, said apparatus comprising:
- (a) means for obtaining luminance data representing luminance of said image for each pixel as a function of said image data;
- (b) means for obtaining color difference data representing differences between said image data of respective color components for each pixel;
- (c) means for obtaining a first statistic representing a standard deviation of said luminance data in each pixel block;
- (d) means for obtaining a second statistic representing a standard deviation of said color difference data in each pixel block;
- (e) means for comparing said first and second statistics with first and second threshold values, respectively, to classify respective pixel blocks into first and second type pixel blocks;
- and
- (f) means for compressing said image data on said first type pixel blocks at a first compression rate and compressing said image data on said second type pixel blocks at a second compression rate to thereby obtain compressed image data, wherein said first compression rate is different from said second compression rate.
Dependencies are inferred from the claim text.