US 6,804,417 B1 · Pixel depletion technique

Abstract

Multiple algorithms are applied to expand input image data of a variety of lower resolutions to output image data of a variety of higher resolutions with enhanced text quality, particularly in the black datapath controlling an output device such as an inkjet or laser printer. Enhancement techniques include edge smoothing, bit stripping for large drop weight pens, and drop-weight based ink depletion. Embodiments provide algorithms that convert 600×600 dpi input resolution data to 1200×600 dpi output resolution image data or 300×300 to 600×300 dpi resolution (i.e., asymmetric 2:1 ratio resolution conversion along mutually perpendicular axes), including text edge smoothing, while causing minimal change to gray scaled (halftoned) data within images. The techniques can be applied to other resolutions as well. Some embodiments include unidirectional bitstripping that preserves 1200 dpi edges while applying output pixels at only 600 dpi from 1200 dpi resolution output image data. Some embodiments include drop-weight based depletion to adjust the average ink flux to 32 ng per {fraction (1/600)}th inch cell, thereby preventing excess ink application at high output resolutions, e.g., 1200×600 dpi. In various embodiments, operations are performed in hardware modules and/or performed cooperatively as an integrated process to meet system throughput requirements.

Claims23

Dependent claims

An input pixel data processing method, wherein each pixel has associated therewith a pixel density and wherein the input pixel data may have associated therewith a gray scale of such pixel densities, the method comprising:

generating an output pixel;
depleting the pixel density of a selected output pixel in a plane containing a plurality of output pixels, including adjusting a drop weight of said selected output pixel,
wherein said selected output pixel is selected by performing logic operations on at least said selected output pixel, said logic operations embodying selection criteria, such selection criteria including:
alignment of said selected output pixel with a preselected position in a two-dimensional depletion array tiled logically across said plane;
and
said selected output pixel and four output pixels immediately adjacent said selected output pixel having a preselected pixel density.

3 more elements

generating an output pixel image in response to said input pixel data;
reducing by pixel thinning the average pixel density of said output pixel image, wherein such output pixel image otherwise delivers excess average pixel density, such pixel thinning comprising:
scanning a first row of given pixels of said output pixel image along a given direction;
determining if said first row of given pixels contains a series of adjacent pixels having dark pixel density;
if so, then
turning off alternate dark density pixels in said series, such that the resulting pixel density of said series is reduced on average by approximately one-half;
scanning a second row of given pixels adjacent said first row of given pixels along said given direction;
and
selectively turning on pixels within and proximate to an end point of said series, thereby preserving edge definition and filling preselected interior spaces within dark pixel density images.

6 more elements

Dependencies are inferred from the claim text.

Pixel depletion technique

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Pixel depletion technique

Life of this patent

Abstract

Claims23