读取dds文件转为opengl纹理
Load DDS's files
struct Vertex
{
float tu, tv;
float x, y, z;
};
Vertex g_quadVertices[] =
{
{ 0.0f,0.0f, -1.0f,-1.0f, 0.0f },
{ 1.0f,0.0f, 1.0f,-1.0f, 0.0f },
{ 1.0f,1.0f, 1.0f, 1.0f, 0.0f },
{ 0.0f,1.0f, -1.0f, 1.0f, 0.0f }
};
//dds 格式
struct DDS_IMAGE_DATA
{
GLsizei width;
GLsizei height;
GLint components;
GLenum format;
int numMipMaps;
GLubyte *pixels;
};
//加载DDS文件
//-----------------------------------------------------------------------------
// Name: loadCompressedTexture()
// Desc:
//-----------------------------------------------------------------------------
void loadCompressedTexture( void )
{
// NOTE: Unlike "lena.bmp", "lena.dds" actually contains its own mip-map
// levels, which are also compressed.
DDS_IMAGE_DATA *pDDSImageData = loadDDSTextureFile( "lena.dds" );
if( pDDSImageData != NULL )
{
int nHeight = pDDSImageData->height;
int nWidth = pDDSImageData->width;
int nNumMipMaps = pDDSImageData->numMipMaps;
int nBlockSize;
if( pDDSImageData->format == GL_COMPRESSED_RGBA_S3TC_DXT1_EXT )
nBlockSize = 8;
else
nBlockSize = 16;
glGenTextures( 1, &g_compressedTextureID );
glBindTexture( GL_TEXTURE_2D, g_compressedTextureID );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
int nSize;
int nOffset = 0;
// Load the mip-map levels
for( int i = 0; i < nNumMipMaps; ++i )
{
if( nWidth == 0 ) nWidth = 1;
if( nHeight == 0 ) nHeight = 1;
nSize = ((nWidth+3)/4) * ((nHeight+3)/4) * nBlockSize;
glCompressedTexImage2DARB( GL_TEXTURE_2D,
i,
pDDSImageData->format,
nWidth,
nHeight,
0,
nSize,
pDDSImageData->pixels + nOffset );
nOffset += nSize;
// Half the image size for the next mip-map level...
nWidth = (nWidth / 2);
nHeight = (nHeight / 2);
}
}
if( pDDSImageData != NULL )
{
if( pDDSImageData->pixels != NULL )
free( pDDSImageData->pixels );
free( pDDSImageData );
}
}
//-----------------------------------------------------------------------------
// Name: loadDDSTextureFile()
// Desc:
//-----------------------------------------------------------------------------
DDS_IMAGE_DATA* loadDDSTextureFile( const char *filename )
{
DDS_IMAGE_DATA *pDDSImageData;
DDSURFACEDESC2 ddsd;
char filecode[4];
FILE *pFile;
int factor;
int bufferSize;
// Open the file
pFile = fopen( filename, "rb" );
if( pFile == NULL )
{
char str[255];
sprintf( str, "loadDDSTextureFile couldn't find, or failed to load \"%s\"", filename );
MessageBox( NULL, str, "ERROR", MB_OK|MB_ICONEXCLAMATION );
return NULL;
}
// Verify the file is a true .dds file
fread( filecode, 1, 4, pFile );
if( strncmp( filecode, "DDS ", 4 ) != 0 )
{
char str[255];
sprintf( str, "The file \"%s\" doesn't appear to be a valid .dds file!", filename );
MessageBox( NULL, str, "ERROR", MB_OK|MB_ICONEXCLAMATION );
fclose( pFile );
return NULL;
}
// Get the surface descriptor
fread( &ddsd, sizeof(ddsd), 1, pFile );
pDDSImageData = (DDS_IMAGE_DATA*) malloc(sizeof(DDS_IMAGE_DATA));
memset( pDDSImageData, 0, sizeof(DDS_IMAGE_DATA) );
//
// This .dds loader supports the loading of compressed formats DXT1, DXT3
// and DXT5.
//
switch( ddsd.ddpfPixelFormat.dwFourCC )
{
case FOURCC_DXT1:
// DXT1's compression ratio is 8:1
pDDSImageData->format = GL_COMPRESSED_RGBA_S3TC_DXT1_EXT;
factor = 2;
break;
case FOURCC_DXT3:
// DXT3's compression ratio is 4:1
pDDSImageData->format = GL_COMPRESSED_RGBA_S3TC_DXT3_EXT;
factor = 4;
break;
case FOURCC_DXT5:
// DXT5's compression ratio is 4:1
pDDSImageData->format = GL_COMPRESSED_RGBA_S3TC_DXT5_EXT;
factor = 4;
break;
default:
char str[255];
sprintf( str, "The file \"%s\" doesn't appear to be compressed "
"using DXT1, DXT3, or DXT5!", filename );
MessageBox( NULL, str, "ERROR", MB_OK|MB_ICONEXCLAMATION );
return NULL;
}
//
// How big will the buffer need to be to load all of the pixel data
// including mip-maps?
//
if( ddsd.dwLinearSize == 0 )
{
MessageBox( NULL, "dwLinearSize is 0!","ERROR",
MB_OK|MB_ICONEXCLAMATION);
}
if( ddsd.dwMipMapCount > 1 )
bufferSize = ddsd.dwLinearSize * factor;
else
bufferSize = ddsd.dwLinearSize;
pDDSImageData->pixels = (unsigned char*)malloc(bufferSize * sizeof(unsigned char));
fread( pDDSImageData->pixels, 1, bufferSize, pFile );
// Close the file
fclose( pFile );
pDDSImageData->width = ddsd.dwWidth;
pDDSImageData->height = ddsd.dwHeight;
pDDSImageData->numMipMaps = ddsd.dwMipMapCount;
if( ddsd.ddpfPixelFormat.dwFourCC == FOURCC_DXT1 )
pDDSImageData->components = 3;
else
pDDSImageData->components = 4;
return pDDSImageData;
}
//渲染
glBindTexture( GL_TEXTURE_2D, g_compressedTextureID );
glInterleavedArrays( GL_T2F_V3F, 0, g_quadVertices );
glDrawArrays( GL_QUADS, 0, 4 );