Patent Number: 6,252,994

Title: Adaptive quantization compatible with the JPEG baseline sequential mode

Abstract: 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.

Inventors: Nafarieh; Asghar (Menlo Park, CA)

Assignee: Xerox Corporation

International Classification: G06T 9/00 (20060101); H04N 7/26 (20060101); H04N 7/30 (20060101); C06K 009/36 (); C06K 009/38 (); C06K 009/46 ()

Expiration Date: 06/26/2018