Systems and methods for reducing boundary artifacts in hybrid compression
AssigneeXerox Corporation
InventorZhigang Fan
Life of this patent
Estimating the term…
Abstract
A recursive dilation method and apparatus reduces the boundary artifacts occurring in hybrid compression. Documents containing both pictures and text are most efficiently compressed using a first compression standard for the picture region and a second compression standard for the text region, and thus inherently produce boundary blocks of both types, but such boundary blocks are most efficiently compressed when they contain only picture data and completely contain picture data, or only text data and completely contain text data. The non-picture data or non-text data in such boundary blocks can be considered “missing” data. The recursive dilation method and apparatus assigns the values of the boundary pixels to the neighboring pixels which have missing data.
Claims20
A method for compressing an image, comprising:
- dividing the image into image segments, the image segments including at least one segment of a first type and at least one segment of a second type, wherein at least each at least one segment of the first type is divided into image blocks and compressed on a block-by-block basis, and at least one of the image blocks of the at least one segment of the first type contains a boundary between data of the first type and missing data, each image block comprising a plurality of pixels, and each pixel having a value;
- identifying each image block containing a boundary with missing data;
- recursively replacing the missing data of each first type boundary block with first type data by assigning the value of a closest boundary pixel;
- compressing each first type image block and each first type boundary block using a first compression technique;
- and
- compressing each at least one segment of the second type using a second compression technique.
An apparatus for compressing an image, comprising:
- an image segmenting portion that divides the image into image segments, the image segments including at least one segment of a first type and at least one segment of a second type;
- a segment blocking portion that divides each at least one segment of the first type into image blocks, on a block-by-block basis, at least one of the image blocks of the at least one segment of the first type containing a boundary between data of the first type and missing data, each image block comprising a plurality of pixels, and each pixel having a value;
- a block analyzer that identifies each image block containing a boundary with missing data;
- a recursive dilation data generator that recursively replaces the missing data of each first type boundary block with first type data by assigning the value of a closest boundary pixel;
- a first compressor that compresses each first type image block and each first type boundary block on a block-by-block basis, using a first compression technique;
- and
- a second compressor that compresses each at least one segment of the second type using a second compression technique.
Dependencies are inferred from the claim text.