title: DXT decompression - ressult differ +/- 1
body: <p>If I compress image using OpenGL (<code>GL_COMPRESSED_RGB_S3TC_DXT1_EXT</code>) and then read back RAW image (OpenGL decompress it for me), I got certain image.</p>
  
  <p>If I follow OpenGL documentation and write my own decompressor, my results are similar, but on certain places they randomly differ in terms of  +/- 1.
  I have tried to round my values during "color blending" in DXT decompressor, but result is still incorrect.</p>
  
  <p>Can it be repaired, or is it non-repairable error caused by GPU float arithmetic and therefor decompressed values are different. </p>