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Introduced new code for detecting DXT1 images catogoriesed as RGB that actually have a 1 bit alpha,

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therefore re-interpreting these as RGBA.
This commit is contained in:
Robert Osfield
2011-04-13 19:26:35 +00:00
parent b62f927eff
commit b1692f1f31
1 changed files with 25 additions and 44 deletions
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69
src/osgPlugins/dds/ReaderWriterDDS.cpp
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@@ -355,7 +355,6 @@ osg::Image* ReadDDSFile(std::istream& _istream)
// while compressed formats will use DDPF_FOURCC with a four-character code.
bool usingAlpha = ddsd.ddpfPixelFormat.dwFlags & DDPF_ALPHAPIXELS;
bool checkIfUsingOneBitAlpha = false;
// Uncompressed formats.
if(ddsd.ddpfPixelFormat.dwFlags & DDPF_RGB)
@@ -511,7 +510,7 @@ osg::Image* ReadDDSFile(std::istream& _istream)
switch(ddsd.ddpfPixelFormat.dwFourCC)
{
case FOURCC_DXT1:
OSG_INFO << "ReadDDSFile info : format = DXT1" << std::endl;
OSG_NOTICE << "ReadDDSFile info : format = DXT1, usingAlpha=" <<usingAlpha<< std::endl;
if (usingAlpha)
{
internalFormat = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
@@ -521,7 +520,7 @@ osg::Image* ReadDDSFile(std::istream& _istream)
{
internalFormat = GL_COMPRESSED_RGB_S3TC_DXT1_EXT;
pixelFormat = GL_COMPRESSED_RGB_S3TC_DXT1_EXT;
checkIfUsingOneBitAlpha = true;
//checkIfUsingOneBitAlpha = true;
}
break;
case FOURCC_DXT3:
@@ -682,50 +681,10 @@ osg::Image* ReadDDSFile(std::istream& _istream)
// this memory will not be used but it will not cause leak in worst meaning of this word.
}
// Check if alpha information embedded in the 8-byte encoding blocks
if (checkIfUsingOneBitAlpha)
{
const DXT1TexelsBlock *texelsBlock = reinterpret_cast<const DXT1TexelsBlock*>(imageData);
// Only do the check on the first mipmap level, and stop when we
// see the first alpha texel
int i = size / sizeof(DXT1TexelsBlock);
bool foundAlpha = false;
while ((!foundAlpha) && (i>0))
{
// See if this block might contain transparent texels
if (texelsBlock->color_0<=texelsBlock->color_1)
{
// Scan the texels block for the '11' bit pattern that
// indicates a transparent texel
int j = 0;
while ((!foundAlpha) && (j < 32))
{
// Check for the '11' bit pattern on this texel
if ( ((texelsBlock->texels4x4 >> j) & 0x03) == 0x03)
{
// Texture is using the 1-bit alpha encoding, so we
// need to update the assumed pixel format
internalFormat = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
pixelFormat = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
foundAlpha = true;
}
// Next texel
j += 2;
}
}
// Next block
--i;
++texelsBlock;
}
}
osgImage->setImage(s,t,r, internalFormat, pixelFormat, dataType, imageData, osg::Image::USE_NEW_DELETE);
if (mipmap_offsets.size()>0) osgImage->setMipmapLevels(mipmap_offsets);
// Return Image.
return osgImage.release();
}
@@ -1004,6 +963,28 @@ public:
{
osg::Image* osgImage = ReadDDSFile(fin);
if (osgImage==NULL) return ReadResult::FILE_NOT_HANDLED;
if (osgImage->getPixelFormat()==GL_COMPRESSED_RGB_S3TC_DXT1_EXT)
{
// check to see if DXT1c (RGB_S3TC_DXT1) format image might actually be
// a DXT1a format image
// temporarily set pixel format to GL_COMPRESSED_RGBA_S3TC_DXT1_EXT so
// that the isImageTranslucent() method assumes that RGBA is present and then
// checks the alpha values to see if they are all 1.0.
osgImage->setPixelFormat(GL_COMPRESSED_RGBA_S3TC_DXT1_EXT);
if (!osgImage->isImageTranslucent())
{
// image contains alpha's that are 1.0, so treat is as RGB
OSG_INFO<<"Image with PixelFormat==GL_COMPRESSED_RGB_S3TC_DXT1_EXT is opaque."<<std::endl;
osgImage->setPixelFormat(GL_COMPRESSED_RGB_S3TC_DXT1_EXT);
}
else
{
// image contains alpha's that are non 1.0, so treat is as RGBA
OSG_INFO<<"Image with PixelFormat==GL_COMPRESSED_RGB_S3TC_DXT1_EXT has transparency, setting format to GL_COMPRESSED_RGBA_S3TC_DXT1_EXT."<<std::endl;
}
}
if (options && options->getOptionString().find("dds_flip")!=std::string::npos)
{