Facsimile and static presentation processing – Static presentation processing – Attribute control
Reexamination Certificate
1998-04-30
2001-07-17
Nguyen, Madeleine (Department: 2622)
Facsimile and static presentation processing
Static presentation processing
Attribute control
C358S523000
Reexamination Certificate
active
06262812
ABSTRACT:
BACKGROUND OF THE INVENTION
1 Field of Invention
This invention generally relates to object-oriented color image value adjustment in a perceptually uniform manner.
2. Description of Related Art
Systems exist that allow a user to create, modify, and print color images. These printing systems typically consist of a general purpose computer, a monitor or other viewing device, and a printer.
Some printing systems allow a user to make contrast and other color adjustments to a printed image. However, these adjustments are typically performed in the monitor's color space or in the printer's color space. Therefore, the resulting changes in the printed image are perceived as highly non-linear and unpredictable when compared to the user-input adjustments. This is because the color spaces that are used to make the adjustments are not visually uniform. That is, the adjustments defined by the user are not carried out by the system in a perceptually uniform manner, as perceived by the human eye.
SUMMARY OF THE INVENTION
Accordingly, this invention provides an image adjusting device and method that performs image adjustment in a perceptually linear manner. For example, image value adjustment is made in a perceptually uniform color space to achieve perceptually linear image adjustment based on user-input control values.
An aspect of the invention provides the ability to define and apply different user-set image object or component adjustment values for different image types, e.g., text, graphics, bitmap, etc.
An aspect of the invention provides adjustment of image values based on user-set image adjustment values and a projection of at least one color balance vector on one of the adjustment color space channels.
An aspect of the invention also provides contrast adjustment of image values based on a sigmoidal function that is influenced by a user-set image adjustment value.
An aspect of the invention also provides scaling of image values based on an input device's color gamut, such as a monitor's or scanner's color gamut, and an output device's color gamut, such as a printer's color gamut, to maximize the dynamic range of image values output from the image adjustment system.
An aspect of the invention also provides a method for generating a look-up table for converting values in an adjustment color space to a printer device color space. To create the lookup table, a test print is generated by a printer using known input values. Measurement data is generated from the test print, and the measured data is inverted in an inversion color space to generate a first lookup table. The first lookup table converts image values from the inversion color space to the printer device space. The measured data is also converted to an adjustment color space. The measured data is not inverted in the adjustment color space to generate the first lookup table because to do so might cause undesirable gamut warping effects that degrade the quality of the color rendering processes. Values in the adjustment color space are scaled to maximize the dynamic range of the values in the adjustment color space. Samples of the scaled values are then converted to the inversion color space, and using the first lookup table, printer color space values corresponding to the scaled values in the adjustment color space are determined. A final lookup table is created by concatenating the determined printer color space values and the scaled values in the adjustment color space. The final lookup table converts values from the adjustment color space to the printer color space.
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HP's DeskJet 560C Makes Snappy Color Printing Simple, Observer, Mar. 1994, pp. 10-12, and 35-36.
Bennett Scott A.
Birnbaum David
Chan Tse-kee
Ebner Fritz F.
Linder Stephen F.
Nguyen Madeleine
Oliff & Berridg,e PLC
Xerox Corporation
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