Canon Kabushiki Kaisha

Yuki Matsumoto

Hiroshi Kajiwara

Naoki Ito

Hirokazu Tamura

Ken-ichi Ohta

Hidefumi Osawa

Haruo Shimizu

An image, in which a character image and a photographic image are mixed, is efficiently encoded while preventing image quality deterioration. Hence, image data including foreground pixels and background pixels is input. In the image data, first image data is generated by setting a pixel value that does not occur as the foreground pixel to the pixel value of the background pixel based on the histogram of pixel values that occur as foreground pixels, and the first image data is encoded. In the image data, second image data is generated by setting a value based on the pixel value of the background pixel to the pixel value of the foreground pixel, and the second image data is encoded.

Image processing apparatus and method

The invention provides an image encoding apparatus which can improve image quality of an output image while further reduce the amount of attribute. A determination unit determines an area including a character/line drawing as a foreground image area based on an input multi-valued image. A foreground image generator generates foreground image in binary representation so that a first encoder performs MMR encoding on the foreground image. A background image generator generates multi-valued background image data by replacing the value of a multi-valued pixel in a position of the character/line drawing in the foreground image area with a replacement value calculated from the pixel values in a position of the non-character/line drawing pixel. A second encoder performs JPEG encoding on the background image. A mask unit masks attribute for pixels within the foreground image area with a predetermined value to output the masked data to a third encoder.

Image encoding apparatus, image processing apparatus and control method thereof

This invention detects an area where image quality greatly changes upon resolution conversion. For this purpose, a block segmentation unit extracts a tile having Tw&#xd7;Th pixels from a buffer, and stores the tile in a tile buffer. A two-colors ratio calculating unit counts the number of times the number of colors included in a surrounding pixel group positioned near a pixel of interest becomes two during raster scanning of the tile buffer, and calculates a two-colors ratio Cr. A continuous pixel ratio calculating unit calculates, as a run ratio Rr, a ratio at which pixels having the same color continue during scanning of the tile buffer. A difference calculating unit calculates a resolution conversion error Dt when an image of the tile is converted to &#xbd; the resolution. A determination unit determines based on Cr, Rr, and Dt whether a tile of interest is suitable for resolution conversion.

Image resolution conversion with error detection

This invention suppresses mixing of different types of encoded data in an image area having a specific image property while allowing mixing of losslessly encoded data and lossily encoded data. For this purpose, an input unit inputs image on an image block basis. A conversion unit converts the resolution of the image data to &#xbd; by generating one pixel from 2&#xd7;2 pixels. A first encoding unit lossily encodes the converted image data. A second encoding unit losslessly encodes the image data for each image block. A selecting unit selects encoded data with a smaller code amount. A determination unit determines whether an image block of interest has a specific image property, and outputs the determination result to the selecting unit. If the image of interest has a specific image property, the selecting unit selects and outputs encoded data of the type set by a control unit in advance.

Image processing apparatus and control method therefor

Image data is efficiently encoded using a predict coding unit and a run-length coding unit. The predict coding unit encodes a target pixel X on the basis of difference between the value of the target pixel and a predict value calculated from pixels neighboring the target pixel. The run-length coding unit starts the measuring the run when the number of colors contained in four pixels 'a', 'b', &#x201c;c&#x201d;, and &#x201c;d&#x201d; near the target pixel X is 1, and outputs encoded data of the run when the target pixel is different from an immediately preceding pixel &#x201c;a&#x201d;. Then, the predict coding unit starts the encoding. At this time, since the target pixel is different from the preceding pixel, the preceding pixel is excluded from references for generating the predict value. Instead of the preceding pixel, an pixel, which has been encoded, satisfying a specific condition is referred to.

Image encoding apparatus, method, and computer-readable storage medium for encoding a pixel value

According to this invention, encoded data of a target data amount is generated by one image input operation while both lossless encoding and lossy encoding are adopted. For this purpose, a first memory stores encoded data of a shorter encode length among encoded data generated by a first encoding unit which performs lossy encoding and encoded data generated by a second encoding unit which performs lossless encoding. A second memory stores encoded data from a second encoding unit. When an encoding sequence control unit determines that the encoded data amount in the first memory has exceeded the target data amount, the encoding sequence control unit discards data in the first memory, sets a quantization parameter for a higher compression ratio for the first encoding unit, and causes the first encoding unit to execute encoding. Encoded data before the encoded data amount is determined to have exceeded the target data amount is re-encoded by a re-encoding unit.

Image encoding apparatus and method, computer program, and computer-readable storage medium

An image having few colors can be losslessly encoded at a higher compression ratio. For this purpose, pixel data are input in raster order and temporarily stored in a buffer. A neighborhood matching determination unit generates first information representing whether a pixel having the same color as that of the pixel of interest exists in neighboring pixels and second information specifying whether a pixel having the same color as that of the pixel of interest exists, and if the pixel having the same color exists, specifying the neighboring pixel. A pixel matching detection unit counts the number of colors contained in the neighboring pixels and generates information representing whether the number of colors is two or less, or three or less. On the basis of the information, a code generation unit outputs one or both of encoded data from a matched-pixel position encoding unit and a prediction error encoding unit.

Image encoding apparatus, image decoding apparatus, control method therefor, computer program, and computer-readable storage medium

An image coding apparatus for efficient coding on image data having discrete pixel values such as a CG image or a limited color image as well as a natural image where pixel value changes are mild. For this purpose, a tile dividing unit divides multi-valued image data into tiles. An occurred level count unit outputs the result of counting of the number of brightness values in the tile to a comparison unit and outputs the existing brightness values to an index table generation unit. The index table generation unit allocates continuous index values to the existing brightness values, and stores the result of allocation into an index memory table. An index conversion unit replaces the input pixel values in the tile with index values, and outputs the index values to a selector. The selector selects one of the brightness values in the tile or the index values based on the result of comparison by the comparison unit, and outputs the selected values to a tile data predictive coding unit so as to perform predictive coding processing.

Growing community of inventors

Kawasaki, Japan

Yuki Matsumoto