06252994 is referenced by 36 patents and cites 23 patents.

Pixel blocks of an input image are type classified based on an analysis of pixel values for each respective pixel block. A discrete cosine transform (DCT) is performed on the pixel values of each pixel block, and a quantization modification process thresholds and/or quantizes the resulting DCT coefficients based on the type classification of the respective pixel block. Once the coefficients are modified in this way and encoded, the resulting data can be decoded and dequantized in compliance with the standard JPEG sequential mode data syntax in order to construct a perceptually faithful representation of the image, without passing any additional information to the decoder concerning the quantization modification.

Title
Adaptive quantization compatible with the JPEG baseline sequential mode
Application Number
9/13485
Publication Number
6252994 (B1)
Application Date
January 26, 1998
Publication Date
June 26, 2001
Inventor
Asghar Nafarieh
Menlo Park
CA, US
Agent
Oliff & Berridge
US
Assignee
Xerox Corporation
CT, US
IPC
C06K 9/36
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