Facsimile and static presentation processing – Natural color facsimile – Specific image-processing circuitry
Patent
1994-08-05
1996-10-08
Vu, Kim Yen
Facsimile and static presentation processing
Natural color facsimile
Specific image-processing circuitry
358515, 358518, 348642, 348645, H04N 965, H04N 968, H04N 146, G03F 308
Patent
active
055637264
ABSTRACT:
In data processing wherein image data are processed by dividing them into blocks, a chroma data W is obtained from the color difference data W.sub.R and W.sub.B, and the color difference data W.sub.R and W.sub.B are corrected according to an amplitude of the chroma data W. For example, if the chroma W is smaller than a prescribed threshold value, the color difference data W.sub.R and W.sub.B are set as zero. Then, the so-called block distortion can be prevented. The degree of the correction may depend on the amplitude of the chroma data W. On the other hand, DC coefficients of discrete cosine transform coefficients of adjacent blocks are compared with each other. When the DC coefficients are different from each other, block distortion occurs if they represent a same image. Then, if differences of DC coefficients of discrete cosine transform coefficients of adjacent blocks are small with each other, the DC coefficients are corrected to tend to have similar values. As to the AC coefficients, a comparator compares absolute values of AC components in the DCT coefficient data received from a discrete cosine transform section with a prescribed threshold value. Then, if absolute values of AC components in the DCT coefficient data are smaller than a prescribed threshold value, the values of the AC components are not sent to a coding section because in such cases read errors or the like are thought to affect the AC components.
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"DCT Image Coding Using Adaptive Quantization Application To Digital Color Copiers" by Kazuyuki Murata (Gazou Denshi Gakkaishi; vol. 20, No. 5 (1991) (467).
Nakatani Munehiro
Sakatani Kazuomi
Suzuki Hiroyuki
Minolta Co. , Ltd.
Vu Kim Yen
Williams Kimberly A.
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