bmp图片格式及读取

C++读取bmp图片的例子

 #include <windows.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <malloc.h> 

 #define WIDTHBYTES(x) ((x+31)/32*4)
 #define my(x)  ( ( (x + 31) & ~31) / 8)

 BITMAPFILEHEADER bf; //BMP文件头结构体
 BITMAPINFOHEADER bi; //BMP信息头结构体

 int i,j;
 RGBQUAD *ipRGB;        //颜色表
 DWORD NumColors;    //颜色表数目
 unsigned char ** Imgdata;

 void read(char*);
 void display();
 void org(char*);
 void gray(char*);

 void test()
 {
     DWORD LineByte;
     DWORD ImgSize;
     LineByte=(DWORD)my(bi.biWidth*bi.biBitCount); //计算位图的实际宽度并确保它为32的倍数
     ImgSize=(DWORD)LineByte*bi.biHeight;
     printf("LineByte            is %d. \n", LineByte);
     printf("ImgSize             is %d. \n", ImgSize);
 }

 int main()
 {
      char *filename;
      filename="U616.bmp";
      read(filename);
      display();
      test();
      org("123.bmp");
      free(Imgdata);
    //  printf("<2>");
    //  display();
      free(ipRGB);
      system("pause");
      return ;
 } 

 void read(char* filename)
 {
     FILE* fp;
     fp=fopen(filename,"rb");
     if(fp == NULL)
     {
         printf("Open file error!");
         exit();
     }

     //读取信息头、文件头
     fread(&bf,sizeof(BITMAPFILEHEADER),,fp);
     fread(&bi,sizeof(BITMAPINFOHEADER),,fp); 

     if (bi.biClrUsed !=  )
         NumColors=(DWORD)bi.biClrUsed;
     else
          switch (bi.biBitCount)
           {
                case :            NumColors=;     break;
              case :            NumColors=;    break;
                case :            NumColors=;   break;
             case :           NumColors=;     break;
         } 

      //分配调色板内存
      ipRGB=(RGBQUAD *)malloc(NumColors*sizeof(RGBQUAD));
      fread(ipRGB,sizeof(RGBQUAD),NumColors,fp); 

      Imgdata=new unsigned char*[bi.biHeight]; //声明一个指针数组
      if(bi.biBitCount==)
      {
          for ( i=(bi.biHeight)-;i>=;i--)
                 Imgdata[i]=new unsigned char[bi.biWidth*]; //每个数组元素也是一个指针数组

          for ( i=(bi.biHeight)-;i>=;i--)
                 for(j=;j<bi.biWidth*;j++)
                   fread(&Imgdata[i][j],,,fp);//每次只读取一个1字节，存入数组
       }
      else
      {
          for ( i=(bi.biHeight)-;i>=;i--)
              Imgdata[i]=new unsigned char[bi.biWidth]; 

          for ( i=(bi.biHeight)-;i>=;i--)
              for(j=;j<bi.biWidth;j++)
                    fread(&Imgdata[i][j],,,fp);
      }

      fclose(fp);
 }

 void org(char *filename)
 {
      FILE* fp;
      fp=fopen(filename,"wb");
      fwrite(&bf,sizeof(BITMAPFILEHEADER),,fp); //写文件头
      fwrite(&bi,sizeof(BITMAPINFOHEADER),,fp); //写信息头
      fwrite(ipRGB,sizeof(RGBQUAD),NumColors,fp);//写颜色头 

      if(bi.biBitCount==)
          for (i=(bi.biHeight)- ;i>=;i--)
               for (j= ;j<my(bi.biWidth*);j++)
                   fwrite(&Imgdata[i][j],,,fp);
      else
          for (i=(bi.biHeight)- ;i>=;i--)
              for (j= ;j<bi.biWidth;j++)
                     fwrite(&Imgdata[i][j],,,fp);
      fclose(fp);
 }

 void gray(char *filename)
 {
      FILE* fp;
      fp=fopen(filename,"wb");
     /*
      bf.bfOffBits=(DWORD)1078;
      bi.biSizeImage=(DWORD)(bi.biWidth*bi.biHeight);
      bf.bfSize=bi.biSizeImage+bf.bfOffBits;
      bi.biBitCount=(WORD)8;
      bi.biClrUsed=(DWORD)256;
      bi.biClrImportant=(DWORD)256;
      bi.biXPelsPerMeter=(LONG)0;
      bi.biYPelsPerMeter=(LONG)0;
      NumColors=(DWORD)bi.biClrUsed;
      ipRGB=(RGBQUAD *)malloc(NumColors*sizeof(RGBQUAD));
      */
      fwrite(&bf,sizeof(BITMAPFILEHEADER),,fp); //写文件头
      fwrite(&bi,sizeof(BITMAPINFOHEADER),,fp); //写信息头
      fwrite(ipRGB,sizeof(RGBQUAD),NumColors,fp);//写颜色头 

      char temp;
      for (i=(bi.biHeight)- ;i>=;i--)
          for (j= ;j<bi.biWidth*;j++)
              if(j%==)
              {
                        temp=(Imgdata[i][j]*+Imgdata[i][j+]*+Imgdata[i][j+]*)>>;
                        fwrite(&temp,,,fp);
              }
              else
              {
                        fwrite(&temp,,,fp);
              }
      fclose(fp);
  }

 void display()
 {
     printf("tagBITMAPFILEHEADER info is: %d\n",sizeof(BITMAPFILEHEADER));
     printf("bfType              is %d.\n", bf.bfType);
     printf("bfSize              is %d.\n", bf.bfSize);
     printf("bfReserved1         is %d.\n", bf.bfReserved1);
     printf("bfReserved2         is %d.\n", bf.bfReserved2);
     printf("bfOffBits           is %d.\n", bf.bfOffBits);

     printf("\ntagBITMAPINFOHEADER info is: %d\n",sizeof(BITMAPINFOHEADER));
     printf("biSize              is %d. \n", bi.biSize);
     printf("biWidth             is %ld.\n", bi.biWidth);
     printf("biHeight            is %ld.\n", bi.biHeight);
     printf("biPlanes            is %d. \n", bi.biPlanes);
     printf("biBitCount          is %d. \n", bi.biBitCount);       //每像素所需位数
     printf("biCompression       is %d. \n", bi.biCompression);
     printf("biSizeImage         is %d. \n", bi.biSizeImage);
     printf("biXPelsPerMerer     is %ld.\n", bi.biXPelsPerMeter);  //每米像素数
     printf("biYPelsPerMerer     is %ld.\n", bi.biYPelsPerMeter);
     printf("biClrUsed           is %d. \n", bi.biClrUsed);
     printf("biClrImportant      is %d. \n", bi.biClrImportant);
     printf("\nNum of colors     is %d. \n", NumColors);
  }