Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-02-05
2001-03-06
Coles, Edward L. (Department: 2722)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S001300, C358S001800, C358S001110, C347S041000, C347S043000
Reexamination Certificate
active
06198543
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to use of compressed image data to address a look-up table, and particularly concerns utilizing compressed RGB color image data to index a look-up table for providing corresponding CMYK data.
2. Description of the Related Art
Recently, 32-bit printer drivers have become available, primarily because 32-bit printer drivers can take advantage of certain features that are available for 32-bit code, but not for 16-bit code. However, for historical reasons many operating systems, such as Windows 95™, are designed to communicate only with 16-bit printer drivers. Therefore, many of the new 32-bit printer drivers actually include both a 16-bit portion, which interfaces with the operating system, as well as a 32-bit portion in which most of the actual processing is performed.
Specifically, the operating system is typically configured to receive RGB (red, green blue) print data from an application program and to provide the RGB data to a 16-bit printer driver. Accordingly, the printer driver uses its 16-bit portion to receive the RGB data. Typically, the 16-bit portion of the driver then immediately either spools the RGB data to a spool file for use by the 32-bit portion or else directly transfers the data to the 32-bit portion of the driver.
Upon receipt of the RGB data, or access to the spool file in the event of spooling, the 32-bit portion ordinarily first performs color matching. Color matching involves converting the input RGB data into CMYK (cyan, magenta, yellow and black) data and frequently includes performing data corrections based on the source of the RGB data. Thereafter, the 32-bit portion of the printer driver performs further additional processing in order to generate data which can be used by the printer.
However, several problems exist with the foregoing conventional configuration. First, the transfer time from the 16-bit portion of the printer driver to the 32-bit portion can be significant, particularly when the 16-bit portion of the driver spools the print data to a spool file. In this regard, the RGB data are usually represented by 8 bits per pixel per color. Accordingly, a single 8½′×11′ page can require the 16-bit portion to spool to disk, and then the 32-bit portion to read from the disk, 33 megabytes of data. Correspondingly, 33 megabytes of disk space generally must be set aside per spooled page.
Moreover, as noted above, upon obtaining the RGB data the 32-bit portion of the conventional printer driver typically performs color matching, requiring additional processing time. Even if caching is used, this step still can consume significant processing time.
SUMMARY OF THE INVENTION
The present invention addresses these problems by providing a technique in which compressed image data can be used to access a look-up table.
In one aspect, compressed color image data are received, including a color table having first format data entries, each of which represents one of a number of different colors in a first data format, also including an index into the color table for each of several pixels. The first format data entries for the different colors are processed so as to obtain second format data entries, each of which represents one of the different colors in a second data format. A look-up table is then generated that includes the second format data entries for the different colors. A second format data value is then obtained for each of the pixels by using the index for the pixel to address the look-up table.
By virtue of the foregoing arrangement, faster conversion from one data format to another can often be achieved. Specifically, the invention allows for using the compressed image data to access a look-up table in order to obtain data in the desired format. Accordingly, in many cases this arrangement eliminates the need to first expand compressed image data before performing format conversion.
Another aspect of the invention is applicable in a windowing operating system where a 16-bit portion of a printer driver provides RGB color data to a 32-bit portion of the printer driver. The RGB color data are compressed in the 16-bit portion and utilized in the 32-bit portion. Specifically, in the 16-bit portion, a color table is generated and output which includes RGB values for each color in a part of the image. Also in the 16-bit portion, the RGB color data are compressed by outputting an index into the color table for each pixel in the part of the image. In the 32-bit portion, several color components, including CMYK components, are calculated for each of a number of colors in the color table and cached. Also in the 32-bit portion, for each of the pixels in the part of the image, the cached color components are accessed using the index into the color table generated in the 16-bit portion.
By virtue of this arrangement, the 16-bit portion of a printer driver can spool or directly transfer data to the 32-bit portion of the driver in an efficient manner. Moreover, according to this aspect of the invention, the received compressed data can be used by the 32-bit portion to index into a cache to perform efficient color matching.
This brief summary has been provided so that the nature of the invention may be understood quickly. A more complete understanding of the invention can be obtained by reference to the following detailed description of the preferred embodiments thereof in connection with the attached drawings.
REFERENCES:
patent: 4763190 (1988-08-01), Froelich
patent: 5402245 (1995-03-01), Motta et al.
patent: 5488398 (1996-01-01), Matsubara et al.
patent: 5500661 (1996-03-01), Matsubara et al.
patent: 5633663 (1997-05-01), Matsubara et al.
Canon Kabushiki Kaisha
Coles Edward L.
Fitzpatrick ,Cella, Harper & Scinto
Lamb Twyler
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