Patent Application
20070279652
An embodiment described below provides a super-resolution encoded (SRE) halftoning system having super-resolution encoding (SRE)/decoding (SRD) capabilities to allow a user to bypass the pre-programmed screens of a printer and achieve the desired image rendering. In particular, a preferred embodiment provides an SRE halftoning engine and SRD module that enables conventional SRE codes to be used in a novel way as building blocks for construction of binary halftone patterns. The SRE halftoning engine utilizes the SRE dot disclosed in co-pending patent application Ser. No. ______, entitled “System and Method for Creating Patterned Encoded Halftones,” by J. McElvain et al. filed on May 31, 2006, herewith, which is incorporated herein by reference in its entirety.
For an 8-bit code specification, there are as many as 256 unique SRE codes, each of which result in a different 3 by 3 bit pattern to be rendered.
The exemplary embodiment describes a method for providing 2400×2400 rendering using a 600×600 SRE halftone description to enable printing of SRE halftones on engines that support SRE/SRD. However, the techniques described herein may be applied in other contexts. For example, a library of other multipixel patterns having a different pattern size of conventional SRE/SRD codes may be used in accordance with the techniques disclosed herein.
As described above, a preferred embodiment enables SRE patterns to be used as building blocks for 2400 dpi halftone construction, whose growth characteristics are similar to traditional halftones specified at higher resolutions. In particular, the preferred embodiment utilizes a new SRE halftone dot description, defined in co-pending patent application Ser. No. ______, entitled “System and Method for Creating Patterned Encoded Halftones,” by J. McElvain et al. filed on May 31, 2006 herewith, for halftoning in a manner analogous to Holladay threshold based design.
Matrix of elements 250 determines the pattern of small dots to represent each incoming corresponding group of pixels of the contone image. Each element 240 is a predetermined threshold level that will be compared with the contone data to determine whether a corresponding dot should be printed.
Halftoner 320 renders intensity or lightness levels by converting the incoming continuous tone image 310 to a halftone image 330. A halftone representation is an approximation of an original image that uses a series of carefully placed dots to create an appearance of continuous tones when viewed from a normal viewing distance. The halftone data is written as binary patterns (dot/no dot) onto a photoreceptor 340 of a printer, such as a production level color xerographic printer. The resulting halftoned image has a binary pattern at a higher resolution than the contone data.
Halftoner 320 uses a particular Holladay dot for rendering the halftone data. For example, upon receipt of an 8-bit pixel of contone data having a gray level of “37,” halftoner 320 compares the raw data to each element 240 within matrix 250 of Holladay dot 200 and writes a pattern to photoreceptor 340 accordingly. In particular, halftoner 320 prints a dot at each pixel that threshold level 240 gray level “37” exceeds and would not print a dot (e.g., leave paper uncolored) at each pixel that threshold level 240 gray level “37” does not exceed.
Referring to
Dots are printed for each row of matrix 250 based upon a comparison of the threshold values to the gray level as described above, thereby producing a brick (e.g., halftoned data) for the gray-level “37.”
A list of thresholds 540 and a list of corresponding SRE codes 550 associated with the thresholds is provided for each of the 9 pixels of SRE dot 500. For each SRE pixel, a list of threshold values 540 and corresponding SRE codes 550 is created to represent Holladay dot 200. For example, threshold values/SRE codes for an upper left pixel of SRE dot 500 is provided at 542. Similarly, threshold values/SRE codes for an upper center pixel of SRE dot 500 is provided at 544. Array 546 corresponds to an upper right pixel of SRE dot 500, and array 548 corresponds to the center left pixel of replicated SRE dot 500.
One of ordinary skill in the art will appreciate that the system is not limited to any particular arrangement of pixels within SRE dot 500.
For example, referring to
Referring to pixel 544, a comparison of the input contone data level “37” to a row of contone levels 560 shows that “37” is greater than “23,” but less than the next level of “48.” Thus, a level of “23” is selected and the corresponding SRE code in the list of threshold values 570 is “7.” The SRE code of 7 is selected by the SRE halftoner and placed in an encoded array of pattern values for the contone level of “37.” The SRD module receives the encoded array and decodes each encoded pattern code into a pattern of binary data. Pixel 640 illustrates the decoding of SRE code “7” by the SRD module.
Similarly, referring to pixel 546, an SRE halftoner compares input contone data level “37” to a row of contone levels 580 and selects the first element in the array, which is “37.” The corresponding SRE code shown in the list of threshold values 590 is “1.” The SRE code of 1 is selected by the SRE halftoner and placed in an encoded array of pattern values for the contone level of “37.” In this example, there are 9 encoded pattern values for a contone level. SRD module receives the encoded array and decodes each encoded pattern code into a pattern of binary data. Pixel 610 illustrates the decoding of SRE code “1” by the SRD module.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.
