Patent ID: 8149469

Claim:
An image reading apparatus having an image sensor in which a plurality of sensors for reading a document image are arranged into a line, the apparatus comprising: a compression unit configured to compress image data of a pixel at one end read by each sensor in the image sensor by a first compression process and to compress image data of remaining pixels in the each sensor in the image sensor by a second compression process different from the first compression process; a storage unit configured to store the image data compressed by said compression unit; a decompression unit configured to decompress the image data output from said storage unit; and a counting unit configured to count the number of pixels input to said decompression unit; wherein when the number of pixels counted by said counting unit matches a predetermined number, said decompression unit changes a decompression process for the image data stored by said storage unit between a first decompression process for the image data compressed by the first compression process and a second decompression process for the image data compressed by the second compression process.