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US 2003/0198397 A1Published application
Image processing system for compressing image data including binary image data and continuous tone image data by a sub-band transform method with a high-compression rate
AssigneeRicoh Company, Ltd.
InventorsNekka Matsuura, Yukiko Yamazaki, Takahiro Yagishita
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Abstract
An image processing system which compresses an image including both a binary image and a continuous tone image by a sub-band transform method with a high compression rate. A 2×2 pixel matrix block is extracted from image data. A transform factor having a plurality of frequency components is obtained from the 2×2 pixel matrix block data. The transform factor is quantized by a fixed-length quantizing method by deleting a predetermined number of lower order bits of each of the frequency components.
Claims10
An image processing system comprising:
- a buffer unit extracting n×m pixel matrix block data from image data, where n and m are integers;
- a binarizing unit transforming the n×m pixel matrix block data into binary data represented by a maximum value and a minimum value;
- differential data calculating unit calculating differential data which is a difference between a value of each pixel in the n×m pixel matrix block data and one of the maximum value and the minimum value of the binary data;
- a sub-band transform unit transforming the differential data by a sub-band transform method so as to obtain a transform factor having a plurality of frequency components;
- and
- an encoding unit encoding the binary data and the sub-band transform factor so as, to obtain a code representing the image data.
3 more elements
An image processing method comprising the steps of:
- extracting n×m pixel matrix block data from image data, where n and m are integers;
- transforming the n×m pixel matrix block data into binary data represented by a maximum value and a minimum value;
- calculating differential data which is a difference between a value of each pixel in the n×m pixel matrix block data and one of the maximum value and the minimum value of the binary data;
- transforming the differential data by a sub-band transform method so as to obtain a transform factor having a plurality of frequency components;
- and
- encoding the binary data and the sub-band-transform factor so as to obtain a code representing the image data.
3 more elements
An image processing system comprising:
- a dividing unit dividing image data into a plurality of n×m pixel matrix block data, where n and m are integers;
- a transform unit transforming each pixel in the n×m pixel matrix block data by a frequency transform method so as to produce a transform factor including a high-frequency component and a low-frequency component;
- an image area discriminating unit for determining whether the block being processed corresponds to an edge area or a non-edge area based on the transform factor output from said transform unit;
- a quantizing unit quantizing the transform factor for the edge area and the transform factor for the non-edge area by different methods;
- and
- an encoding unit encoding an output of said quantizing unit by an entropy encoding method,
- wherein a total of a number of bits of the high-frequency component and a number of bits of the low-frequency is the same regardless of types of the edge area or the non-edge area, and a number of bits of the high-frequency component for the edge area is the same as a number of bits of the low-frequency component of the non-edge area.
4 more elements
An image processing method comprising the steps of:
- dividing image data into a plurality of n×m pixel matrix block data, where n and m are integers;
- transforming each pixel in the n×m pixel matrix block data by a frequency transform method so as to produce a transform factor including a high-frequency component and a low-frequency component;
- determining whether the block being processed corresponds to an edge area or a non-edge area based on the transform factor output from said transform unit;
- quantizing the transform factor for the edge area and the transform factor for the non-edge area by different methods;
- and
- encoding an output of said quantizing unit by an entropy encoding method,
- wherein a total of a number of bits of the high-frequency component and a number of bits of the low-frequency is the same regardless of types of the edge area or the non-edge area, and a number of bits of the high-frequency component for the edge area is the same as a number of bits of the low-frequency component of the non-edge area.
4 more elements
Dependencies are inferred from the claim text.