读取dds文件转为opengl纹理

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 );