Quote Originally Posted by Pocus
Quote Originally Posted by Clootie
Use DXT1 for 4bit per texel, or DXT2-5 for 8bit per texel. DXT1 is 1-bit alpha format.
thanks, tried the DXT2. Microsoft says its a compressed texture format, but how exactly are spread the RGB pixels in it? Is it 2/3 pixels for each color?

Anyway it slightly reduce my memory usage (the app going from 270 to 250 Mb of max memory usage) but at the expense of a far bigger texturing time (to the point that my cache system is too slow.
MS has a description on MSDN.
Actually DXT2 & DXT4 formats are [almost] not used now. And it's really strange that you are seeing slowdown with DXTx texture formats - they should be faster to texture from (due to their size). That video card are you using? Maybe slowdown is because you are compresing textures at application run-time? Compressing is actually slow procedure and should be taken offline.

How can I keep reading from the disk the image files? Does a possibility exists to keep the images in memory but untextured and in a very compressed state.
Question doesn't sound right. Can you refrase it?
You can load files containing textures just in any allocated by you memory. And after this (for example) create D3D textures by D3DXCreateTextureFromFileInMemmory()