Image-processing apparatus, image-processing method, program and computer readable information recording medium

Abstract

An image processing apparatus and method for decompressing compressed image data is described. In one embodiment, the image processing apparatus decompresses compressed image data that is obtained by dividing an original image into blocks and compressing each block. The apparatus may comprise a decompression unit to decompress the compressed image data to provide an image which is a collection of the respective blocks, and a smoothing unit to perform a smoothing operation on the decompressed image to control the smoothing effect applied to the image based on distance from a block boundary and based on an edge amount.

1 . An image processing apparatus for generating image data from a code stream coded with the use of wavelet transform, comprising:
 a tag processing unit to interpret tag information added to the code stream and decomposes the code stream into coded streams of respective tiles of respective components;   an inverse quantization unit by which a target bit position to decode is determined in an order based on the tag information, and to a context is generated from peripheral bits of the target bit;   an entropy decoding unit to generate the target bit by decoding with probability estimation with the context and the code stream, and to write the target bit in the target bit position;   a wavelet inverse transform unit to perform an inverse wavelet transform on the decoded data from the entropy decoding unit, and to restore the respective tiles of the respective components of the image data;   a color space inverse transform unit to generate the image data with color space inverse transform from the restored data from the wavelet inverse transform unit; and   a tile boundary smoothing unit to perform smoothing processing on a tile boundary part of the image data generated by the color space inverse transform unit, wherein the tile boundary smoothing unit changes coefficients of a lowpass filter according to a distance of a pixel of the image data from the tile boundary.   
     
     
         2 . The image processing apparatus defined in  claim 1 , wherein the distance of the pixel of the image data is obtained in such a manner that the minimum distance from among those of the pixel from the vertical and horizontal boundaries is retarded as the distance of the pixel from the tile boundary. 
     
     
         3 . The image processing apparatus defined in  claim 1 , wherein the tile boundary smoothing unit reduces the smoothing effect of the lowpass filter as the distance of the pixel of the image data from the tile boundary increases. 
     
     
         4 . The image processing apparatus defined in  claim 1 , wherein the tile boundary smoothing unit changes the coefficients of the lowpass filter according to the distance of the pixel from the tile boundary and an edge amount of the pixel near the tile boundary. 
     
     
         5 . An image processing method for generating image data from a code stream coded with the use of wavelet transform, the method comprising:
 interpreting tag information added to the code stream and decomposing the code stream into coded streams of respective tiles of respective components;   determining a target bit position to decode in an order based on the tag information, and generating a context from peripheral bits of the target bit;   generating the target bit by decoding with probability estimation with the context and the code stream, and writing the target bit in the target bit position;   performing an inverse wavelet transform on the decoded data from said entropy decoding part, and restoring the respective tiles of the respective components of the image data to create restored data;   generating the image data with color space inverse transform from the restored data; and   performing smoothing processing on a tile boundary part of the image data generated with the color space inverse transform, including changing coefficients of a lowpass filter according to a distance of a pixel of the image data from the tile boundary.   
     
     
         6 . The method defined in  claim 5 , wherein the distance of the pixel of the image data is obtained in such a manner that the minimum distance from among those of the pixel from the vertical and horizontal boundaries is retarded as the distance of the pixel from the tile boundary. 
     
     
         7 . The method defined in  claim 5 , wherein performing smoothing processing on a tile boundary part of the image data comprises reducing the smoothing effect of the lowpass filter as the distance of the pixel of the image data from the tile boundary increases. 
     
     
         8 . The method defined in  claim 5 , wherein performing smoothing processing on a tile boundary part of the image data comprises changing the coefficients of the lowpass filter according to the distance of the pixel from the tile boundary and an edge amount of the pixel near the tile boundary. 
     
     
         9 . An article of manufacture having one or more computer-readable storage media storing instructions which, when executed by a system, cause the system to perform an image processing method for generating image data from a code stream coded with the use of wavelet transform, the method comprising:
 interpreting tag information added to the code stream and decomposing the code stream into coded streams of respective tiles of respective components;   determining a target bit position to decode in an order based on the tag information, and generating a context from peripheral bits of the target bit;   generating the target bit by decoding with probability estimation with the context and the code stream, and writing the target bit in the target bit position;   performing an inverse wavelet transform on the decoded data from said entropy decoding part, and restoring the respective tiles of the respective components of the image data to create restored data;   generating the image data with color space inverse transform from the restored data; and   performing smoothing processing on a tile boundary part of the image data generated with the color space inverse transform, including changing coefficients of a lowpass filter according to a distance of a pixel of the image data from the tile boundary.   
     
     
         10 . The article of manufacture defined in  claim 9 , wherein the distance of the pixel of the image data is obtained in such a manner that the minimum distance from among those of the pixel from the vertical and horizontal boundaries is retarded as the distance of the pixel from the tile boundary. 
     
     
         11 . The article of manufacture defined in  claim 9 , wherein performing smoothing processing on a tile boundary part of the image data comprises reducing the smoothing effect of the lowpass filter as the distance of the pixel of the image data from the tile boundary increases. 
     
     
         12 . The article of manufacture defined in  claim 9 , wherein performing smoothing processing on a tile boundary part of the image data comprises changing the coefficients of the lowpass filter according to the distance of the pixel from the tile boundary and an edge amount of the pixel near the tile boundary.