Half tone image enhancement for printers
AssigneeHitachi Koki Imaging Solutions, Inc.
InventorJae Hwal Yoo
Life of this patent
Estimating the term…
Abstract
A method and apparatus for halftoning over a region of output pixels by defining large, or macro, halftone cells corresponding to regions of contiguous pixels and partitioning the macro halftone cells into smaller halftone cells. The gray, or hue, level within a macro halftone cell is determined by the number of pixels which are darkened within the macro halftone cell. Selection of the number of pixels to be darkened in response to input data can be effected in a manner to achieve automatic gamma correction.
Claims20
A method for halftoning in an area defined by a matrix of pixels comprising:
- partitioning the area into a plurality of macro halftone cells, each macro halftone cell being constituted by an array of contiguous pixels;
- defining a plurality of ranking levels, each ranking level being associated with a linear function of a desired level of apparent color intensity in a macro halftone cell region, a highest ranking level being associated with a minimum apparent color intensity and a lowest ranking level being associated with a maximum apparent color intensity;
- allocating to each ranking level one or more pixels of each macro halftone cell such that the pixels of the macro halftone cell are non-uniformly distributed among the plurality of ranking levels;
- selecting one of the ranking levels for each macro halftone cell based upon an input value associated with the macro halftone cell;
- and
- in each macro halftone cell, darkening each pixel allocated to a ranking level greater than the ranking level selected for the macro halftone cell,
- wherein the pixels of each macro halftone cell are non-uniformly allocated among the ranking levels such that the apparent level of color intensity of each macro halftone cell is linearly proportional to the associated input value.
A system for halftoning in an area defined by a matrix of pixels comprising:
- means for partitioning the area into a plurality of macro halftone cells, each macro halftone cell being constituted by an array of contiguous pixels;
- means for defining a plurality of ranking levels, each ranking level being associated with a linear function of a desired level of apparent color intensity in a macro halftone cell region, a highest ranking level being associated with a minimum apparent color intensity and a lowest ranking level being associated with a maximum apparent color intensity level;
- means for allocating to each ranking level one or more pixels of each macro halftone cell such that the pixels of the macro halftone cell are non-uniformly distributed among the plurality of ranking levels;
- means for selecting one of the ranking levels for each macro halftone cell based upon an input value associated with the macro halftone cell;
- and
- means for darkening, in each macro halftone cell, each pixel allocated to a ranking level which is greater than the ranking level for the macro halftone cell,
- wherein the pixels of each macro halftone cell are non-uniformly allocated among the ranking levels such that the apparent level of color intensity of each macro halftone cell is linearly proportional to the associated input value.
Dependencies are inferred from the claim text.