Image compressing apparatus and image decoding apparatus and image converting apparatus and image processing method

An image compression apparatus including a block division unit that executes block division of an image, a first compression unit that compresses information, which discriminates between a first predetermined pixel value and another pixel value with respect to the divided image, to first compression data, and a second compression unit that compresses the divided image to second compression data,

• wherein when the information, which discriminates between the predetermined pixel value and said another pixel value, is compressed with respect to the block, the second compression unit executes image compression by replacing at least one of the first predetermined pixel value and said another pixel value of the block with a first predetermined value or a second predetermined value.

An image compression apparatus comprising:

• a first compression unit that compresses information, which indicates white and non-white with respect to an image, to first compression data;
• and
• a second compression unit that compresses the image to second compression data.

An image compression apparatus including a block division unit that executes block division of an image, a first compression unit that compresses information, which indicates white and non-white with respect to the divided image, to first compression data, and a second compression unit that compresses the divided image to second compression data,

• wherein when the information, which indicates white and non-white, is compressed with respect to the block in the first compression unit, the second compression unit executes image compression by replacing a white pixel of the block with a pixel other than the white pixel.

An image decoding apparatus that decodes compression data, in which an image that is composed of a plurality of signals is compressed as first and second compression data and at least an arbitrary one of the plurality of signals is compressed in one of the first and second compression data,

• wherein a decoded result of one of the first and second compression data is adopted for a signal that is included in both the first compression data and the second compression data.

An image decoding apparatus that decodes first compression data, which includes information that discriminates between a predetermined pixel value and another pixel value, and second compression data in which an image is compressed,

• wherein as regards a decoded image of the second compression data, a pixel that is indicated as having the predetermined pixel value by decoding the first compression data is corrected to the predetermined pixel value.

An image converting apparatus that handles codes, in which codes that are produced by encoding an image by a plurality of encoding schemes in units of a block are mixedly present and at least one of the encoding schemes is selected for each block,

• wherein a code, which is produced by a specified encoding scheme, is taken out of the codes, and the code that is produced by the specified encoding scheme is output as a substitute when there is no code corresponding to the block.

An image processing method that executes such a process that as regards compression data that is produced by fixed-length compressing a block-divided image by at least one of first and second compression schemes, significant information in each compression unit of arbitrary compression data is replaced with other compression data that is compressed by at least one of the first and second compression schemes.