Coder, coding method, program, and image forming apparatus for improving image data compression ratio
AssigneeMinolta Co., Ltd.
InventorNobuhiro Mishima
Life of this patent
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Abstract
The present invention discloses a coder and a coding method that raise the possibility of improving the compression ratio of multivalued image data in which one pixel consists of a plurality of bits and are accordingly effective to increase the amount of image that is stored in a recording medium with a certain capacity. The coder according to the present invention includes an obtaining unit for obtaining a predetermined amount of image data in which one pixel consists of a plurality of bits, a developing unit for developing on the virtual plane each piece of the bit data in the obtained image data, and a coding unit for performing the entropy coding on the developed bit data.
Claims21
An image data coder for coding multivalued image data in which a value of each pixel is expressed by a plurality of bits, comprising:
- a reading unit operable to read the multivalued image data per predetermined number of pixels;
- a generating unit operable to generate, from the values of each read plurality of pixels, fixed-length gradation characteristic data expressing a gradation characteristic of the pixels, and fixed-length quantized data obtained by quantizing each pixel value into a plurality of bits using a predetermined threshold value;
- a dividing unit operable to divide the generated data into the gradation characteristic data, and pieces of bit data each formed from bits in a same position of bit strings, in the quantized data, corresponding one-to-one with the pixels;
- and
- a coding unit operable to entropy code at least part of the divided data.
An image data coding method for coding multivalued image data in which a value of each pixel is expressed by a plurality of bits, comprising the steps of:
- reading the multivalued image data per predetermined number of pixels;
- generating, from the values of each read plurality of pixels, fixed-length gradation characteristic data expressing a gradation characteristic of the pixels, and fixed-length quantized data obtained by quantizing each pixel value into a plurality of bits using a predetermined threshold value;
- dividing the generated data into the gradation characteristic data, and pieces of bit data each formed from bits in a same position of bit strings, in the quantized data, corresponding one-to-one with the pixels;
- and
- entropy coding at least part of the divided data.
A computer-readable recording medium storing a computer program that realizes processing for coding multivalued image data in which a value of each pixel is expressed by a plurality of bits, the computer program causing a computer to execute the steps of:
- reading the multivalued image data per predetermined number of pixels;
- generating, from the values of each read plurality of pixels, fixed-length gradation characteristic data expressing a gradation characteristic of the pixels, and fixed-length quantized data obtained by quantizing each pixel value into a plurality of bits using a predetermined threshold value;
- dividing the generated data into the gradation characteristic data, and pieces of bit data each formed from bits in a same position of bit strings, in the quantized data, corresponding one-to-one with the pixels;
- and
- entropy coding at least part of the divided data.
A computer-readable recording medium storing computer coded data generated by (i) reading, per predetermined number of pixels, multivalued image data in which a value of each pixel is expressed by a plurality of bits, (ii) generating, from the values of each read plurality of pixels, fixed-length gradation characteristic data expressing a gradation characteristic of the pixels, and fixed-length quantized data obtained by quantizing each pixel value into a plurality of bits using a predetermined threshold value, (iii) dividing the generated data into the gradation characteristic data, and pieces of bit data each formed from bits in a same position of bit strings, in the quantized data, corresponding one-to-one with the pixels, and (iv) entropy coding at least part of the divided data.
Dependencies are inferred from the claim text.