Digital copying machine, image reading device used in said digital copying machine, and image processing method used in these devices

An image scanning device comprising:

• a document reader for reading an original document and generating image data corresponding to the original document;
• an input image memory for storing the image data generated by the document reader;
• an image data dividing manager for dividing the image data stored in the input image memory into a plurality of blocks arranged along an auxiliary scanning direction;
• a compression device which compresses the image data on a per block basis;
• an expansion device which expands the compressed image data on the per block basis;
• an end of document detector for detecting an end of the original document in the auxiliary scanning direction;
• and
• an ineffective area detector which, when the end of document detector detects the end of the original document during compression of image data belonging to one block, sets an area from the end of the original document to the end of the one block as an ineffective area, which causes the expansion device to terminate expansion of the one block upon reaching the ineffective area.

A method of image processing, performed in an image forming device that comprises a plurality of expansion devices for expanding compressed data, said method comprises the steps of:

• reading an original document and generating image information which corresponds to the original document;
• dividing the image information into a plurality of image information blocks along at least an auxiliary scanning direction, wherein the number of image information blocks along the auxiliary scanning direction is set to an integer number greater than one times the number of expansion devices;
• compressing the image information on a per block basis;
• expanding the compressed image information in parallel, on the per block basis, by the plurality of expansion devices, in an order such that expansion of a current row of blocks is completed prior to beginning expansion of any blocks from a next row, and such that none of the expansion devices are required to suspend operation to permit completing the expansion of said current row of blocks;
• and
• reproducing an image of the original document by printing the expanded image information on paper sheets.

A method of image processing, performed in an image forming device that comprises an expansion device for expanding compressed data, said method comprises the steps of:

• reading an original document and generating image data which corresponds to the original document;
• storing the image data in an input image memory;
• dividing the image data stored in the input image memory into a plurality of blocks along an auxiliary scanning direction;
• compressing the image data on a per block basis;
• expanding the compressed image data on the per block basis;
• sensing an end of the original document in the auxiliary scanning direction;
• and
• when the end of the original document is sensed during compression of image data belonging to one block, setting an area from the end of the original document to the end of the one block as an ineffective area and causing the expansion device to terminate expansion of the one block upon reaching the ineffective area.