Image compression device, image decompression device, image compression/decompression device, program for executing on a computer to perform functions of such devices, and recording medium storing such a program
An image compression device comprising an image division unit dividing an image into a plurality of regions, a region designation unit designating a region of interest in the image, a quantization rate determination unit determining quantization rate with respect to each region divided by the image division unit, and a compression control unit controlling compression with respect to each region based on the quantization rate determined by the quantization rate determination unit is disclosed. In the image compression device, the quantization rate determination unit can determine quantization rate for the region of interest different from the quantization rate for the regions other than the region of interest.
1. An image compression device, comprising:
a division unit to divide an image into a plurality of regions;
a wavelet transform unit to apply a wavelet transform on the plurality of regions;
a region designation unit to designate a region of interest for a part of the image that is of interest;
a level of interest setting unit to set a level of interest for each region of interest;
a quantization rate setting unit to set a quantization rate for each wavelet transformed region, according to the level of interest, wherein when the quantization rate of the region of interest is set higher than quantization rates of the other regions, the image quality of the region of interest becomes coarser, while, when the quantization rate of the region of interest is set lower than quantization rates of the other regions, the image quality of the region of interest becomes finer;
a compression control unit to control compression for each region based on the quantization rate;
a quantization unit to perform quantization based on the quantization rate on the compression controlled region; and
an entropy encoding unit to perform entropy encoding on quantized data generated by the quantization unit.
2. The image compression device as claimed in claim 1 , wherein:
at least one of the plurality of regions comprises a tile, and the tile is set to have a tile size such that the tile covers a human face in the image.
3. An image compression method, comprising:
dividing an image into a plurality of regions;
applying a wavelet transform to the plurality of regions;
designating a region of interest for a part of the image that is of interest;
setting a level of interest for each region of interest;
setting a quantization rate for each wavelet transformed region, according to the level of interest, wherein when the quantization rate of the region of interest is set higher than quantization rates of the other regions, the image quality of the region of interest becomes coarser, while, when the quantization rate of the region of interest is set lower than quantization rates of the other regions, the image quality of the region of interest becomes finer;
controlling compression for each region based on the quantization rate;
performing quantization based on the quantization rate on the each region after compression; and performing entropy encoding on the quantized data.
4. The image compression method as claimed in claim 3 , wherein:
at least one of the plurality of regions comprises a tile, and the tile is set to have a tile size such that the tile covers a human face in the image.
5. An article of manufacture having one or more computer-readable storage media storing instructions thereon which, when executed by a system, cause the system to perform an image compression method comprising:
dividing an image into a plurality of regions;
applying a wavelet transform to the plurality of regions;
designating a region of interest for a part of the image that is of interest;
setting a level of interest for each region of interest;
setting a quantization rate for each wavelet transformed region, according to the level of interest, wherein when the quantization rate of the region of interest is set higher than quantization rates of the other regions, the image quality of the region of interest becomes coarser, while, when the quantization rate of the region of interest is set lower than quantization rates of the other regions, the image quality of the region of interest becomes finer;
controlling compression for each region based on the quantization rate;
performing quantization based on the quantization rate on the each region after compression; and
performing entropy encoding on the quantized data.
6. The article of manufacture as claimed in claim 5 , wherein:
at least one of the plurality of regions comprises a tile, and the tile is set to have a tile size such that the tile covers a human face in the image.