US 2004/0104917 A1Published application

Alpha correction to compensate for lack of gamma correction

AssigneeMicrosoft Corporation

InventorsJohn C. Platt, Mikhail M. Lyapunov

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Abstract

The blending coefficients (alpha values) of font glyphs undergo alpha correction to compensate for a lack of gamma correction in text rendering processes. The alpha correction includes selecting a set of correction coefficients that correspond to the predetermined gamma value of the display device and computing corrected alpha values from the known alpha values, the foreground colors, and set of correction coefficients. The corrected alpha values can then be used to blend the foreground and background colors of the corresponding display pixels without requiring gamma correction. Accordingly, the alpha correction can be performed by a GPU, which is not configured to perform gamma correction, thereby increasing the speed at which text rendering can occur.

Claims26

Dependent claims

In a computing system that is connected with a display device having a plurality of pixels configured to display an image, the computing system including a graphics processing unit that is configured to perform a blending process with alpha values to control foreground and background colors of the pixels displaying the image, a method for correcting the alpha values received by the graphics processing unit to enable display of the image at the display device and without gamma correction, the method comprising:

an act of receiving an set of correction coefficients for one or more predetermined gamma values, at least one of the predetermined gamma values comprising the gamma value of the display device;
an act of receiving filtered alpha values that can be used to perform a graphics blending process by the graphics processing unit to determine the foreground and background colors of the pixels displaying the image at the display device;
an act of receiving one or more foreground colors of the pixels;
a step for performing alpha correction on the filtered alpha values to obtain corrected alpha values, said alpha correction utilizing the correction coefficients and the foreground colors;
and
an act of performing a graphics blending process with the corrected alpha values, operating on the foreground and background colors of the pixels, to determine the pixel values used to display the image at the display device.

3 more elements

an act of receiving a set of correction coefficients for one or more predetermined gamma values, at least one of the predetermined gamma values comprising the gamma value of the display device;
an act of receiving one or more filtered alpha values that can be used for a graphics blending process by the graphics processing unit to determine the foreground and background colors of the pixels displaying the image at the display device;
an act of receiving one or more foreground colors;
an act of selecting the set of correction coefficients that correspond to the gamma value of the display device;
an act of computing the corrected alpha values with the filtered alpha values, the foreground colors, and the selected set of correction coefficients;
and
an act of performing a graphics blending process with the corrected alpha values, operating on the foreground and background colors of the pixels, to determine the pixel values used to display the image at the display device.

4 more elements

A computer program product for use in a computing system that is connected with a display device having a plurality of pixels configured to display an image, the computing system including a graphics processing unit that is configured to perform a blending process with alpha values to control foreground and background colors of the pixels displaying the image, the computer program product comprising one or more computer-readable media having computer-executable instructions for implementing a method for correcting the alpha values received by the graphics processing unit to enable display of the image at the display device and without gamma correction, the method comprising:

an act of receiving a set of correction coefficients for one or more predetermined gamma values, at least one of the predetermined gamma values comprising the gamma value of the display device;
an act of receiving one or more filtered alpha values that can be used for a graphics blending process by the graphics processing unit to determine the foreground and background colors of the pixels displaying the image at the display device;
an act of receiving one or more foreground colors;
an act of selecting the set of correction coefficients that correspond to the gamma value of the display device;
an act of computing the corrected alpha values with the filtered alpha values and the selected set of correction coefficients, said act of computing utilizing the correction coefficients and the foreground colors;
and
an act of performing a graphics blending process with the corrected alpha values, operating on the foreground and background colors of the pixels, to determine the pixel values used to display the image at the display device.

4 more elements

Dependencies are inferred from the claim text.