Image analysis – Image compression or coding – Adaptive coding
Patent
1995-02-08
1997-01-28
Couso, Jose L.
Image analysis
Image compression or coding
Adaptive coding
382207, 382248, 3582612, 358430, 358432, G06K 936, G06K 946
Patent
active
055984843
ABSTRACT:
Apparatus for encoding an image signal which is capable of improving the quality of a reproduced image with respect to not only a general image in which electric power is concentrated in low-frequency region coefficients but also an image where the electric power is concentrated in a high-frequency region. The apparatus comprises a blocking device in which a rectangular area in an image is detected from a digital image signal as a pixel block, and is subjected to an orthogonal transform by a converter to obtain a transformed coefficient. In addition, an activity calculator calculates the variance of the image within the block, and electric power to be preserved during encoding is determined by a power-preservation-rate determining device on the basis of the variance determined. An optimum mask is selected by a mask selector on the basis of a transformed coefficient from the converter and a power preservation rate from the power-preservation-rate determining device, and the selection of the transformed coefficient is performed by a coefficient selector by means of this mask. The transformed coefficient after being selected is quantized by a quantizer, is encoded to be outputted through a transmission line.
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Kamizawa Koh
Koshi Yutaka
Kunitake Setsu
Suzuki Kazuhiro
Bella Matthew C.
Couso Jose L.
Fuji 'Xerox Co., Ltd.
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