Opaque pixels lose color with DXT1a

[GoogleCodeExporter]

What steps will reproduce the problem?
1.  Using the nvcompress tool, specify only one format as:
compressionOptions.setFormat(nvtt::Format_DXT1a);
compressionOptions.setQuantization(false, true, true, 0);
2. Run "nvcompress -alpha red.tga" with the attached texture.
3. Open the output DDS and view the RGBA channels.

What is the expected output? What do you see instead?

The input texture is entirely red with an alpha value of 75% across the entire 
thing.  Due to the binary alpha and dithering, the texture will be quantized 
into a red texture with a mixture of fully opaque and fully transparent pixels. 
 As observed from debugging, the texture is correct until passed into the DXT1a 
compressor.  The resulting texture has correct alpha values but the red channel 
has been completely dropped from opaque pixels.

Please use labels and text to provide additional information.

Bug reproduced using trunk revision 1134.
Refer to forum discussion:
http://developer.nvidia.com/forums/index.php?showtopic=4900

Original issue reported on code.google.com by code...@gmail.com on 21 Jul 2010 at 2:11

Attachments:

• red.tga

[GoogleCodeExporter]

This issue was closed by revision r1135.

Original comment by cast...@gmail.com on 22 Jul 2010 at 9:23

• Changed state: Fixed

[GoogleCodeExporter]

Thanks for the bug report and repro case! This is fixed in trunk now.

Original comment by cast...@gmail.com on 22 Jul 2010 at 10:03

• Added labels: Type-Defect