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[font=arial, sans-serif]I've released a new open-source tool and library that some people here may find useful:[/font][/font]

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[font=arial, sans-serif]Advanced DXTn Texture Compression Library Now Available at Google Code[/font]
http://code.google.com/p/crunch/

[font=arial, sans-serif]crunch/crnlib is an open source (ZLIB license), lossy texture [/font]compression tool and library for developers that distribute and use content in the DXT1/5/N or 3DC/BC5 compressed mipmapped texture formats.

[font=arial, sans-serif]crnlib can compress mipmapped 2D textures and cubemaps to .8-1.25 [/font]bits/texel, and normal maps to 1.75-2 bits/texel. crnlib's quality and performance is competitive to transform based solutions, or other offline/real-time DXTn compressors such as squish or ATI_Compress.

[font=arial, sans-serif]crnlib implements a new form of "clustered" DXTn compression, with a [/font]compressed texture data format that was carefully designed to be very quickly transcodable directly to raw DXTn texture bits with no intermediate recompression step or individual pixel-level operations. The typical single threaded transcode to DXTn rate is equivalent to 100-250 megatexels/sec. Fast random access to individual mipmap levels is supported.[/font]

-Rich

Thanks for sharing!
I've only had a quick glance at the project page, but from what I gather, your focus is on achieving great on-disk BPP results (via the intermediate format and/or LZMA-friendly output bytes), rather than focusing on better on-GPU quality when compared to offline compression via squish/nVidia/ATI/etc?

That's right Hodgman. As far as I know, crunch is the first open-source DXTn compression library that allows you to purposely trade off a small amount of quality (in a hopefully perceptually friendly way) for much smaller disk files, faster downloads, or to free up memory.

It can also do regular (block by block) DXTn compression, like libsquish or ATI_Compress. When used in this way, it usually beats both libraries in a PSNR or RMSE sense, but only by a tiny (visually imperceptible) amount.

-Rich