Jpeg2000 to DXT5n

[ericfriedman]

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

[Vladimir_Dudnik · Accepted solution]

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

[ericfriedman]

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

Eric