Ericsson Texture Compression
Encyclopedia
Ericsson Texture Compression (ETC) is a texture compression
technique developed in collaboration with Ericsson Research in early 2005. It was originally developed under the name iPACKMAN and based on an earlier compression scheme called PACKMAN.
The original 'ETC1' compression scheme provides 6x compression of 24 bit RGB data. It does not support the compression of images with Alpha components. The 'ETC2' scheme expands ETC1 in a backwards-compatible way to provide higher quality RGB compression, as well as compression of RGBA data (RGB plus alpha).
ETC1 takes 4x4 groups of pixel
data and compresses each into a single 64 bit word. The 4x4 pixel group is first divided into two 4x2 chunks - either horizontally or vertically. Each half is given a base color - either using 4/4/4 RGB or by giving one of them a 5/5/5 RGB and having the other be a 3/3/3 bit offset from that base. Each 4x2 region also has a 3 bit brightness range selection. Each pixel is then offset from the base color by adding one of four signed values to the base color for its half of the 4x4 group.
This format is a part of the OpenGL ES
graphics standard extensions for embedded devices such as cellphones and has been approved by the Khronos Group
for use in the WebGL
graphics standard for browser-side world-wide web graphics.
A software package called etcpack for compression and decompression of ETC1 textures is available for free download for usage with Khronos APIs.
Android version 2.2 (Froyo) includes support for ETC1.
Texture compression
Texture compression is a specialized form of image compression designed for storing texture maps in 3D computer graphics rendering systems. Unlike conventional image compression algorithms, texture compression algorithms are optimized for random access....
technique developed in collaboration with Ericsson Research in early 2005. It was originally developed under the name iPACKMAN and based on an earlier compression scheme called PACKMAN.
The original 'ETC1' compression scheme provides 6x compression of 24 bit RGB data. It does not support the compression of images with Alpha components. The 'ETC2' scheme expands ETC1 in a backwards-compatible way to provide higher quality RGB compression, as well as compression of RGBA data (RGB plus alpha).
ETC1 takes 4x4 groups of pixel
Pixel
In digital imaging, a pixel, or pel, is a single point in a raster image, or the smallest addressable screen element in a display device; it is the smallest unit of picture that can be represented or controlled....
data and compresses each into a single 64 bit word. The 4x4 pixel group is first divided into two 4x2 chunks - either horizontally or vertically. Each half is given a base color - either using 4/4/4 RGB or by giving one of them a 5/5/5 RGB and having the other be a 3/3/3 bit offset from that base. Each 4x2 region also has a 3 bit brightness range selection. Each pixel is then offset from the base color by adding one of four signed values to the base color for its half of the 4x4 group.
This format is a part of the OpenGL ES
OpenGL ES
OpenGL for Embedded Systems is a subset of the OpenGL 3D graphics application programming interface designed for embedded systems such as mobile phones, PDAs, and video game consoles. OpenGL ES is managed by the not-for-profit technology consortium, the Khronos Group, Inc.- Versions :Several...
graphics standard extensions for embedded devices such as cellphones and has been approved by the Khronos Group
Khronos Group
The Khronos Group is a not-for-profit member-funded industry consortium based in Beaverton, Oregon, focused on the creation of open standard, royalty-free APIs to enable the authoring and accelerated playback of dynamic media on a wide variety of platforms and devices...
for use in the WebGL
WebGL
WebGL is a software library that extends the capability of the JavaScript programming language to allow it to generate interactive 3D graphics within any compatible web browser...
graphics standard for browser-side world-wide web graphics.
A software package called etcpack for compression and decompression of ETC1 textures is available for free download for usage with Khronos APIs.
Android version 2.2 (Froyo) includes support for ETC1.