OpenGL是专业的图形程序接口，功能非常强大，调用方便的底层图形库。本文汇总了运用OPENGL加载BMP纹理图的几个实现方法。
方法一：
首先获取位图句柄：
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HBITMAP hBmp = (HBITMAP) ::LoadImage (AfxGetResourceHandle(),MAKEINTRESOURCE(IDB_BITMAP1), IMAGE_BITMAP, 0, 0,LR_CREATEDIBSECTION);
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然后根据位图句柄得到位图信息：
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BITMAP BM;
::GetObject (hBmp, sizeof (BM), &BM);
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最后根据位图信息中的RGB值建立纹理：
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gluBuild2DMipmaps( GL_TEXTURE_2D, 3, BM.bmWidth, BM.bmHeight,GL_BGR_EXT, GL_UNSIGNED_BYTE,BM.bmBits);
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方法二：
首先用OpenGL辅助库获得位图信息：
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AUX_RGBImageRec* TextureImage[1];
TextureImage[0]=auxDIBImageLoad("1.bmp");
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然后建立纹理
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gluBuild2DMipmaps(GL_TEXTURE_2D, 3, TextureImage[0]->sizeX, TextureImage[0]->sizeY, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->data);
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方法三：
从底层做，需要了解bmp文件的结构，首先读取bmp文件结构，包括文件头、信息头和数据，数据用于后面定义纹理
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long ImageWidth=256;
long ImageHeight=256;
GLubyte Image[256][256][3];
void ReadHeader(FILE *fp , BITMAPFH * p_bitmapheader , BITMAPIH *p_bitmapinfo)
{
fseek(fp, 0, SEEK_SET) ;
fread( &p_bitmapheader->bfType,sizeof(unsigned short), 1, fp );
fseek(fp, 2, SEEK_SET) ;
fread( &p_bitmapheader->bfSize,sizeof(unsigned long), 1, fp );
fseek(fp, 6, SEEK_SET) ;
fread( &p_bitmapheader->bfReserved1,sizeof(unsigned short), 1, fp );
fseek(fp, 8, SEEK_SET) ;
fread( &p_bitmapheader->bfReserved2,sizeof(unsigned short), 1, fp );
fseek(fp, 10, SEEK_SET) ;
fread( &p_bitmapheader->bfOffBits,sizeof(unsigned long), 1, fp );
fseek(fp, 14, SEEK_SET) ;
fread( &p_bitmapinfo->biSize, sizeof(unsigned long), 1, fp );
fseek(fp, 18, SEEK_SET) ;
fread( &p_bitmapinfo->biWidth, sizeof(unsigned long), 1, fp );
fseek(fp, 22, SEEK_SET) ;
fread( &p_bitmapinfo->biHeight, sizeof(unsigned long), 1, fp );
fseek(fp, 26, SEEK_SET) ;
fread( &p_bitmapinfo->biPlanes, sizeof(unsigned short), 1, fp );
fseek(fp, 28, SEEK_SET) ;
fread( &p_bitmapinfo->biBitCount, sizeof(unsigned short), 1, fp );
fseek(fp, 30, SEEK_SET) ;
fread( &p_bitmapinfo->biCompression, sizeof(unsigned long), 1, fp );
fseek(fp, 34, SEEK_SET) ;
fread( &p_bitmapinfo->biSizeImage, sizeof(unsigned long), 1, fp );
fseek(fp, 38, SEEK_SET) ;
fread( &p_bitmapinfo->biXPelsPerMeter, sizeof(unsigned long), 1, fp );
fseek(fp, 42, SEEK_SET) ;
fread( &p_bitmapinfo->biYPelsPerMeter, sizeof(unsigned long), 1, fp );
fseek(fp, 46, SEEK_SET) ;
fread( &p_bitmapinfo->biClrUsed, sizeof(unsigned long), 1, fp );
fseek(fp, 50, SEEK_SET) ;
fread( &p_bitmapinfo->biClrImportant, sizeof(unsigned long), 1, fp );
}
void ReadBitmapFile()
{
BITMAPFH bitmapheader ;
BITMAPIH bitmapinfo ;
FILE *fp;
fp = fopen("6.bmp" , "r") ;
if(!fp)
{
puts("Read file failed.") ;
return;
}
ReadHeader(fp, &bitmapheader , &bitmapinfo) ;
if(bitmapinfo.biBitCount != 24)
{
puts("UNSUPPORT") ;
return;
}
ImageWidth = bitmapinfo.biWidth;
ImageHeight = bitmapinfo.biHeight;
int i=bitmapheader.bfOffBits;
while(i<bitmapheader.bfSize)
{
for(int j=0;j<ImageWidth;j++)
for(int k=0;k<ImageHeight;k++)
{
fseek(fp, i, SEEK_SET) ;
fread(Image[j][k]+2, 1, 1, fp) ;
fseek(fp, i+1, SEEK_SET) ;
fread(Image[j][k]+1, 1, 1, fp) ;
fseek(fp, i+2, SEEK_SET) ;
fread(Image[j][k], 1, 1, fp) ;
i=i+3;
}
}
fclose(fp) ;
}
glTexImage2D(GL_TEXTURE_2D,0,3,ImageWidth,ImageHeight,0,GL_RGB,GL_UNSIGNED_BYTE,&Image[0][0][0]);
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#include <gl\glext.h>
这是因为后面的GL_BGR_EXT是定义在这个头文件里的，因为BMP格式是按Blue,Green,Red顺序储存图像数据的，这与OpenGL中正好相反。GL_BGR_EXT就是完成两者之间的转换的。
下面就是不用AUX库来加载BMP图片作为纹理的函数：
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bool LoadTexture(LPTSTR szFileName, GLuint &texid) // Creates Texture From A Bitmap File
{
HBITMAP hBMP; // Handle Of The Bitmap
BITMAP BMP; // Bitmap Structure
glGenTextures(1, &texid); // Create The Texture
hBMP=(HBITMAP)LoadImage(GetModuleHandle(NULL), szFileName, IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION | LR_LOADFROMFILE );
if (!hBMP) // Does The Bitmap Exist?
return FALSE; // If Not Return False
GetObject(hBMP, sizeof(BMP), &BMP); // Get The Object
// hBMP: Handle To Graphics Object
// sizeof(BMP): Size Of Buffer For Object Information
// &BMP: Buffer For Object Information
glPixelStorei(GL_UNPACK_ALIGNMENT, 4); // Pixel Storage Mode (Word Alignment / 4 Bytes)
// Typical Texture Generation Using Data From The Bitmap
glBindTexture(GL_TEXTURE_2D, texid); // Bind To The Texture ID
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); // Linear Min Filter
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); // Linear Mag Filter
glTexImage2D(GL_TEXTURE_2D, 0, 3, BMP.bmWidth, BMP.bmHeight, 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, BMP.bmBits);
DeleteObject(hBMP); // Delete The Object
return TRUE; // Loading Was Successful
}
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