Color key preservation during sample rate conversion

Abstract

The color-keyed regions of a color-keyed image are extracted from the color-keyed image, and the color-keyed regions and the non-color-keyed regions are independently scaled. The independently scaled regions are subsequently merged to form a scaled color-key image with clearly distinguished color-keyed regions and non-color-keyed regions. To minimize the blurring of edges in the non-color-key regions, the non-color-key colors are extended into color-keyed regions after the color-keyed information is extracted from the color-keyed image. To minimize the encroachment of the scaled color-keyed regions into the scaled non-color-keyed regions of the scaled color-key image, the edges of the scaled color-key regions are sharpened by defining the color-keyed region as the region wherein each scaled/filtered color-key value exceeds a non-zero threshold value. To facilitate the use of existing memory and structure in images that are encoded using three components per pixel, such as RGB, YUV, etc., the extracted color-keyed regions are stored in the memory structure that is typically used to store an optional fourth component, such as a transparency or texture parameter.

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