Texture compression based on two hues with modified brightness

Abstract

In an image-encoding scheme, an input image is decomposed into image blocks (600) comprising multiple image elements (610). The image blocks (600) are then encoded into encoded blocks (700). An encoded block (700) comprises a first color codeword (710), a second color codeword (720), a color modifier codeword (730) and a color index sequence (740). The color codewords (710, 720) are representations of a first and second base color (10, 20) located on a first line (40) in color space. The modifier codeword (730) is a representation of at least one color modifier for modifying the first base color (10) along a second line (12) to obtain multiple color representations (30, 32, 34, 35, 36, 38) along the line (12). The second line (12) has a different direction (15) as compared to the first line (40). The index sequence (740) comprises color indices associated with a color representation selected from i) the representations (30, 32, 34, 35, 36, 38) on the second line (12) and ii) at least one representation (31, 33) based on the second base color (20).

Description

technical field

[0001] The present invention relates generally to image processing, and more particularly to methods and systems for encoding and decoding images. Background technique

[0002] Real-time rendering of 3D graphics has many attractive applications on mobile terminals, including gaming, human-machine interface, messaging, and mobile commerce. Since 3D rendering is a computationally expensive task, dedicated hardware must often be built to achieve adequate performance. Therefore, innovative ways to reduce the complexity and bandwidth usage of such hardware architectures are extremely important.

[0003] Especially for mobile phones the main bottleneck is memory bandwidth. A common technique for reducing memory bandwidth usage is texture compression. Texture mapping represents the process of "gluing" an image (referred to here as a texture) onto a rendering triangle. Large bandwidth usage can be avoided if textures are compressed in memory and then decompressed...

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