Data processor for image data using orthogonal transformation

Details Data processor for image data using orthogonal transformation Data processor for image data using orthogonal transformation

1994-06-28

1996-05-14

Coles, Sr., Edward L.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358426, 358427, 358433, 382232, 382246, 382250, 382251, 348384, 348403, 348405, H04N 140, H04N 141

Patent

active

055173276

ABSTRACT:
In a data processor, image data of a pixel matrix is subjected to orthogonal transformation to coefficient data, the coefficient data is quantized with a first quantization table for character image and a second quantization table for half-tone image, and the image data is discriminated to be character image data or half-tone image data according to the quantization data. The selected data is then coded. In another processor, image data are divided into first and second processing blocks of m*m and M*M pixel matrices wherein M>m and the second processing block includes one of first processing blocks and adjacent pixels. Image data in a first and second processing block are subjected to orthogonal transformation to coefficient data. It is discriminated according to the coefficient data of the second processing block if the image is a character, dot, or half-tone image to select an appropriate quantization table, and image data of the first block is quantized according to the selected table and the quantized data are coded. In a further processor, two discrimination windows are provided, the first having coefficient data around the DC component and the second having the other data. Orthogonal transform coefficients of image data in a processing block are calculated, and maximum of absolute values in the windows are obtained. An image is discriminated to be a dot image if the maximum of the first window is larger than the second and larger than a threshold value.

REFERENCES:
patent: 4903142 (1990-02-01), Hasebe et al.
patent: 5101438 (1992-03-01), Kanda et al.
"DCT Image Coding Using Adaptive Quantization Application to Digital Color Copiers," Kazuyuki Murata, Gazou Denshi Gakkaishi, vol. 20, No. 5 (1991) pp. 467-475.

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