Image compression method, image compression device, image transmission system, data compression pre-processing apparatus, and computer program

An image compression apparatus comprising:

• preprocessing means for preprocessing input image data;
• and
• data compressing means for performing a data compression processing on preprocessed image data, wherein
• said preprocessing means includes:
• filtering region dividing means for dividing said input image data into a plurality of filtering regions;
• region designating means for discriminating important regions from unimportant regions in said input image data;
• and filtering means for performing a filtering processing on said unimportant regions for each of said filtering regions to attenuate the high frequency component of said input image data,
• said data compressing means includes:
• block region dividing means for dividing said preprocessed image data into the plurality of block regions, each shape of which is rectangular;
• orthogonal transforming means for performing an orthogonal transform processing on said image data for each of said block regions;
• and quantizing means for quantizing said image data that has been subjected to said orthogonal transform processing for each of said block regions,
• each of said filtering regions is a cluster which is smaller than said block regions, and which is consisting of one or more adjacent rectangular regions, each of the rectangular regions being obtained by equally dividing each of said block regions by 2n (where n is a natural number) and each having a size of two or more pixels, and
• said filtering processing is performed using a low-pass filter common to said respective filtering regions.

An image transmission system in which a preprocessing apparatus is connected to a data compression apparatus through a first communication line, and in which said data compression apparatus is connected to a data expansion apparatus through a second communication line, wherein

• said preprocessing apparatus includes:
• the filtering region dividing means for dividing input image data into a plurality of filtering regions;
• region designating means for discriminating important regions from unimportant regions in said input image data;
• filtering means for performing a filtering processing on said unimportant regions for each of said filtering regions to attenuate a high frequency component of said input image data;
• and data transmission means for transmitting said image data that has been subjected to said filtering processing to said first communication line,
• said data compression apparatus includes:
• block region dividing means for dividing preprocessed image data into a plurality of block regions, each shape of which is rectangular;
• orthogonal transforming means for performing an orthogonal transform processing on said image data for each of said block regions;
• quantizing means for quantizing said image data that has been subjected to said orthogonal transform processing for each of said block regions;
• and data transmitting means for transmitting encoded image data to said data expansion apparatus through said second communication line,
• each of the filtering regions is a cluster which is smaller than said block region, and which is consisting of one or more adjacent rectangular regions, each of the rectangular regions being obtained by equally dividing each of said block regions by 2n (where n is a natural number) and each having a size of two or more pixels, and
• said filtering processing is performed using a low-pass filter common to said respective filtering regions.

A data compression preprocessing apparatus for preprocessing image data input to a data compression apparatus that divides said image data into a plurality of rectangular block regions, each shape of which is rectangular, and that performs an orthogonal transform and a quantization on said input data for each of the block regions, the data compression preprocessing apparatus comprising:

• filtering region dividing means for dividing said input image data into a plurality of filtering regions;
• region designating means for discriminating important regions from unimportant regions in said input image data;
• and
• filtering means for performing a filtering processing on said unimportant regions for each of said filtering regions to attenuate a high frequency component of said input image data, wherein
• each of said filtering regions is a cluster which is smaller than said block region, and which is consisting of one or more adjacent rectangular regions, each of the rectangular regions being obtained by equally dividing each of said block regions by 2n (where n is a natural number) and each having a size of two or more pixels, and
• said filtering processing is performed using a low-pass filter common to said respective filtering regions.

A computer program for preprocessing image data input to a data compression apparatus that divides said input image data into a plurality of block regions each shape of which is rectangular, and that performs an orthogonal transform and a quantization on said input image data for each of said block regions, the computer program comprising procedures for executing:

• a filtering region dividing step of dividing said input image data into a plurality of filtering regions;
• a region designating step of discriminating important regions from unimportant regions in said input image data;
• and
• a filtering step of performing a filtering processing on said unimportant regions for each of the filtering regions to attenuate a high frequency component of said input image data, wherein
• each of said filtering regions is a cluster which is smaller than said block region, and which is consisting of one or more adjacent rectangular regions, each of the rectangular regions being obtained by equally dividing each of said block regions by 2n (where n is a natural number) and each having a size of two or more pixels, and
• said filtering processing is performed using a low-pass filter common to said respective filtering regions.