Jpeg2000 to DXT5n

ericfriedman — Thu, 21 Apr 2011 20:26:38 GMT

Hello,

I have a normal map saved as a JP2. Using the UIC codecs and the CIPPImage class, I want to load in the JP2, then convert it to a DXT5, but with the source red channel placed in the destination alpha channel.

Here is my code:

CStdFileInput inStream;
inStream.Open("test.jp2")
PARAMS_JPEG2K params;
ZeroMemory(&params, sizeof(PARAMS_JPEG2K));
params.nthreads = 2;
CIppImage image;

ReadImageJPEG2000(inStream, params,image);
CStdFileOutput outStream;
ioutStream.Open("test.dds")
CIppImage alphaImage;
image.ToRGBA32(alphaImage);
int dxt5Order[4] = { 3, 1, 2, 0 };
alphaImage.SwapChannels(dxt5Order);
PARAMS_DDS ddsParams;
ZeroMemory(&ddsParams, sizeof(ddsParams));
ddsParams.ac = 1;
ddsParams.nthreads = 2;
ddsParams.fmt = DDS_DXT5;
SaveImageDDS(alphaImage, ddsParams, outStream);

The resulting image is a gray-scale texture and a blank alpha channel. I get the same result whether or not I call SwapChannels on alphaImage, which leads me to believe that SaveImageDDS isn't handling something properly with 4 channel textures, or toRGBA32 is bugged. That or I'm doing something wrong, which is more likely :)

Does anyone see something is wrong w/ my approach?

Thank you,
Eric

Jpeg2000 to DXT5n

Vladimir_Dudnik — Thu, 21 Apr 2011 21:11:53 GMT

Hi Eric,

I think you should specify ddsParams.ac = 0 (to not add Alpha channel, as you already converted image to 4-channels). You may also need to specify ddsParams.ycocg = 0 - to prevent convertion to YCoCg color space before encoding to DXT5 format.

Regards,
Vladimir

Jpeg2000 to DXT5n

ericfriedman — Thu, 21 Apr 2011 22:32:40 GMT

Thanks Vladimir. I was confused as to what the .ac meant. Setting it to zero fixed the issue.

Eric

topic Jpeg2000 to DXT5n in Intel® Integrated Performance Primitives

Jpeg2000 to DXT5n

Jpeg2000 to DXT5n

Jpeg2000 to DXT5n