Method and apparatus for image rotation with reduced memory using JPEG compression
AssigneeXerox Corporation
InventorsFelice A. Micco, Martin E. Banton
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Abstract
The present invention is a method and apparatus for the rotation of images in conjunction with a block-wise, variable-length data compression operation. In a preferred embodiment, the rotation of image blocks on a microscopic level is accomplished independently from the rotation of the blocks themselves (macroscopic), stored in electronic precollation memory and the rotated image produced upon decompression of the stored rotated data. The two stage process allows the use of standardized JPEG or similar variable-length compression schemes, thereby accomplishing the rotation in conjunction with compression and minimizing the need for large memory buffers to accomplish image rotation
Claims13
A method for rotating a digital image in accordance with a compression operation, the method comprising the steps of:
- dividing the digital image into blocks, each block being represented by digital data;
- rotating the digital data in each block;
- compressing the digital data for each block into a coded unit;
- creating a pointer associated with each of a plurality of coded units after a first coded unit, wherein at least one pointer points to a coded unit other than the coded unit compressed immediately preceding the coded unit with which the pointer is associated;
- storing the coded units and associated pointers in an electronic precollation memory;
- retrieving from the electronic precollation memory the coded units in an order determined by the pointers associated with each coded unit, the order of retrieval being such that no coded unit is decompressed immediately following a block which immediately preceded the coded unit in the compressing step;
- and
- decompressing the coded units retrieved from the electronic precollation memory so as to produce a rotated image.
An apparatus for rotating a digital image in accordance with a JPEG compression operation, comprising:
- a segmenter, said segmenter dividing the digital image into equally sized blocks, each block being represented by digital data;
- a rotation circuit for rotating the digital data in each block in one of a plurality of orthogonal increments;
- a compression processor, said processor compressing the digital data for each block into a coded unit;
- local memory, associated with the compression processor, said local memory storing a pointer associated with each of a plurality of coded units after a first coded unit, wherein each pointer stored therein indicates a coded unit other than the coded unit compressed immediately preceding the coded unit with which the pointer is associated;
- and
- electronic precollation memory for storing the coded units and associated pointers, wherein the data stored in the electronic memory represents a rotated-compressed digital image.
Dependencies are inferred from the claim text.