Image compression
AssigneeHewlett-Packard Indigo B.V.
InventorsGidi Amir, Doron Shaked, Ruth Bergman, Gitit Ruckenstein, Leonid Vygodner, Alexander Spivakovsky, Andrey Iossifov
Life of this patent
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Abstract
A method for compressing a digital image to be printed, the image consisting of pixels. It is determined, for blocks of pixels, whether a block contains a graphical structure that is to be maintained without loss because it is of a type that can be accurately perceived by a human observer. The block is encoded losslessly into a less voluminous format, if such a graphical structure has been found. Otherwise, the block is compressed lossily, if no such graphical structure has been found.
Claims23
A method for compressing a digital image to be printed, the image consisting of pixels, the method comprising:
- determining by a processor of a computing device, for blocks of pixels, whether a block contains a graphical structure that is to be maintained without loss because it is of a type that can be accurately perceived by a human observer, by:
- determining that the block includes just one of black and white pixels, black and transparent pixels, and white and transparent pixels, and that the block contains one or more of a horizontal line and a vertical line;
- encoding by the processor the block losslessly into a less voluminous format, if such a graphical structure has been found;
- compressing by the processor the block lossily, if no such graphical structure has been found.
A computer, programmed to compress an image to be printed by a compression method comprising:
- determining by a processor of the computer, for blocks of pixels, whether a block contains a graphical structure that is to be maintained without loss because it is of a type that can be accurately perceived by a human observer, by:
- determining that the block includes just one of black and white pixels, black and transparent pixels, and white and transparent pixels, and that the block contains one or more of a horizontal line and a vertical line;
- encoding by the processor the block losslessly into a less voluminous format, if such a graphical structure has been found;
- compressing by the processor the block lossily, if no such graphical structure has been found.
A printing system arranged to print an image, which the printing systems receives in a compressed representation, the printing system comprising a processor programmed to decode the compressed representation, the compressed representation having the following characteristics:
- blocks, each having a multiplicity of pixels, containing a graphical structure of a type that can be accurately perceived by a human observer are encoded losslessly in a less voluminous format than that of a bitmap representation of the pixels of the block, the blocks comprising:
- a block including just one of black and white pixels, black and transparent pixels, and white and transparent pixels, and containing one or more of a horizontal line and a vertical line;
- blocks not containing such graphical structures have been compressed lossily.
A computer program product which is in the form of a non-transitory machine-readable medium with program code stored on it,
- wherein the program code is arranged to carry out a method for compressing an image to be printed, the method comprising:
- determining, for blocks of pixels, whether a block contains a graphical structure that is to be maintained without loss because it is of a type that can be accurately perceived by a human observer, by:
- determining that the block includes just one of black and white pixels, black and transparent pixels, and white and transparent pixels, and that the block contains one or more of a horizontal line and a vertical line;
- encoding the block losslessly into a less voluminous format, if such a graphical structure has been found;
- compressing the block lossily, if no such graphical structure has been found.
Dependencies are inferred from the claim text.