Data processor

Details Data processor Data processor

1996-01-25

1999-02-23

Lee, Thomas D.

Facsimile and static presentation processing

Facsimile

Specific signal processing circuitry

358426, 358433, 382232, 382251, 348384, H04N 140, H04N 141

Patent

active

058750410

ABSTRACT:
In a data processor, in order to perform coding efficiently, image data of a prescribed pixel matrix is subjected to orthogonal transformation to coefficient data. Obtained coefficient data is quantized with a first quantization table for character image, and they are also quantized with a second quantization table for half-tone image. Then, the image data is discriminated to be a character image data or a half-tone image data according to the two quantization data. Then, quantization data in correspondence to the discrimination is subjected to entropy coding. In a different data processor, in order to discriminate a kind of image in a processing block fast and correctly, image data are divided into first processing blocks of m*m pixel matrices and second processing blocks of M*M pixel matrices wherein M>m. For example, m=8 and M=16. A second processing block includes one of first processing blocks and adjacent pixels around it. Image data in a first processing block and image dat in a second processing block including the first processing block are subjected to orthogonal transform to send coefficient data, respectively. It is discriminated according to the coefficient data of the second processing block if the image is a character image, a dot image or a half-tone image to select an appropriate quantization table. Then, image data of the first processing block is quantized according to the selected quantization table and quantized data are coded. In a further data processor, in order to discriminate a dot image in a processing block, two discrimination windows are provided, and a first of the windows consists of coefficient data around the DC component while a second consists of the other data. First, orthogonal transform coefficients of image data in a processing block are calculated, and maximum of absolute values in the two windows are obtained. An image is discriminated to be a dot image if the maximum of the first window is larger than that of the second and the former is larger than a prescribed threshold value.

REFERENCES:
patent: 4903142 (1990-02-01), Hasebe et al.
patent: 5101438 (1992-03-01), Kanda et al.
patent: 5333211 (1994-07-01), Kanda et al.
patent: 5422736 (1995-06-01), Katayama

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