Opengl读取TGA图片信息代码
首先是了解opengl里AUX_RGBImageRec的定义，它包含图片宽高和数据
typedef struct _AUX_RGBImageRec {
GLint sizeX,sizeY;
unsignedchar *data;
} AUX_RGBImageRec;
然后就是从TAG图片里提取出这些信息放入AUX_RGBImageRec的对象
想从TAG图片里提取出这些信息得了解TAG图片文件格式，至于格式读者请自行了解如第12到16字节保存了图像宽和高第18字节以后保存了图像数据域
AUX_RGBImageRec* CMap::LoadTGA(char *filename)
{
AUX_RGBImageRec* TGAImage=newAUX_RGBImageRec;
GLubyte TGAheader[12]={0,0,2,0,0,0,0,0,0,0,0,0}; //Uncompressed TGA Header，图像类型码 置2
GLubyte TGAcompare[12]; //Used To Compare TGA Header
GLubyte header[6]; //First 6 Useful Bytes From The Header
GLuint bytesPerPixel; //Holds Number Of Bytes Per Pixel Used In The TGA File
GLuint imageSize; //Used To Store The Image Size When Setting Aside Ram
GLuint temp; //Temporary Variable
GLuint type=GL_RGBA; //Set The Default GL Mode To RBGA (32 BPP)
FILE *file = fopen(filename,"rb"); //Open The TGA File
if( file==NULL|| //Does File Even Exist?
fread(TGAcompare,1,sizeof(TGAcompare),file)!=sizeof(TGAcompare)|| // Are There 12 Bytes To Read?
memcmp(TGAheader,TGAcompare,sizeof(TGAheader))!=0 || //Does The Header Match What We Want?
fread(header,1,sizeof(header),file)!=sizeof(header)) //If So Read Next 6 Header Bytes
{
if (file ==NULL) //Did The File Even Exist? *Added Jim Strong*
returnfalse; //Return False
else
{
fclose(file); //If Anything Failed, Close The File
returnfalse; //Return False
}
}
TGAImage->sizeX = header[1] * 256 +header[0]; // 宽和高以16位字保存，所以要读高位和地位Width (highbyte*256+lowbyte)
TGAImage->sizeY = header[3] * 256+header[2]; //Determine The TGAHeight (highbyte*256+lowbyte)
if( TGAImage->sizeX <=0 || //Is The Width Less Than Or Equal To Zero
TGAImage->sizeY <=0 || //Is The Height Less Than Or Equal To Zero
(header[4]!=24&&header[4]!=32)) //Is The TGA 24 or 32 Bit? RGB或RGBA
{
fclose(file); //If Anything Failed, Close The File
returnfalse; //Return False
}
bytesPerPixel =header[4]/8; //Divide By 8 To Get The Bytes Per Pixel
imageSize =TGAImage->sizeX*TGAImage->sizeY*bytesPerPixel; //Calculate The Memory Required For The TGA Data
TGAImage->data=(GLubyte*)malloc(imageSize); // ReserveMemory To Hold The TGA Data
if( TGAImage->data==NULL|| //Does The Storage Memory Exist?
fread(TGAImage->data,1, imageSize, file)!=imageSize) // Does The ImageSize Match The Memory Reserved?
{
if(TGAImage->data!=NULL) //Was Image Data Loaded
free(TGAImage->data); //If So, Release The Image Data
fclose(file); //Close The File
returnfalse; //Return False
}
for(GLuint i=0;i
temp=TGAImage->data[i]; //Temporarily Store The Value At Image Data 'i'
TGAImage->data[i]= TGAImage->data[i + 2]; // Set The1st Byte To The Value Of The 3rd Byte
TGAImage->data[i+ 2] =temp; //Set The 3rd Byte To The Value In 'temp' (1st Byte Value)
}
fclose(file); //Close The File
return TGAImage;
}