Image analysis – Color image processing – Compression of color images
Patent
1995-02-01
1999-07-27
Kelley, Christopher S.
Image analysis
Color image processing
Compression of color images
382176, 382250, G06K 934
Patent
active
059303867
ABSTRACT:
The invention is intended to prevent deterioration in image quality of an image comprising a mixture of a natural image area, a color character image area, etc. in a process of ADCT multi-value color image compression. In the ADCT process, input image data is separated in units of different image areas based on DCT coefficients after DCT. A quantization factor and a quantization table dedicated for natural image are used for the natural image area. For the color character image area, any suitable one of several quantization factors is selected depending on magnitude of an absolute value of the DCT coefficient, and a quantization table dedicated for character is used for quantization. With this arrangement, deterioration of the color character image, particularly, difference in deterioration of characters between different colors, can be prevented.
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Canon Kabushiki Kaisha
Kelley Christopher S.
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