Opengl中位图贴图的三种方式

转自：http://www.maoyeah.com/display.asp?boardid=3&id=31

OpenGL中用bmp图片做纹理贴图的三种方法

方法一：

首先获取位图句柄

HBITMAP hBmp = (HBITMAP) ::LoadImage (AfxGetResourceHandle(),
                        MAKEINTRESOURCE(IDB_BITMAP1), IMAGE_BITMAP, 0, 0,
                        LR_CREATEDIBSECTION);

然后根据位图句柄得到位图信息

BITMAP BM;
        ::GetObject (hBmp, sizeof (BM), &BM);

最后根据位图信息中的RGB值建立纹理

 gluBuild2DMipmaps( GL_TEXTURE_2D, 3, BM.bmWidth, BM.bmHeight, GL_BGR_EXT, GL_UNSIGNED_BYTE, BM.bmBits );

方法二：

首先用OpenGL辅助库获得位图信息

 AUX_RGBImageRec* TextureImage[1];

 TextureImage[0]=auxDIBImageLoad("1.bmp");

然后建立纹理

 gluBuild2DMipmaps(GL_TEXTURE_2D, 3, TextureImage[0]->sizeX, TextureImage[0]->sizeY, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->data);

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

long ImageWidth=256;
long ImageHeighāt=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 );<ābr/> 
 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,&Imaāge[0][0][0]);