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. 
", LineByte);             
    printf("ImgSize             is %d. 
", 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 0; 
} 

void read(char* filename)
{
    FILE* fp;
    fp=fopen(filename,"rb"); 
    if(fp == NULL)
    {
        printf("Open file error!");
        exit(0);
    }

    //读取信息头、文件头
    fread(&bf,sizeof(BITMAPFILEHEADER),1,fp); 
    fread(&bi,sizeof(BITMAPINFOHEADER),1,fp); 
    
    if (bi.biClrUsed != 0 ) 
        NumColors=(DWORD)bi.biClrUsed; 
    else 
         switch (bi.biBitCount) 
          {    
               case 1:            NumColors=2;     break; 
             case 4:            NumColors=16;    break; 
               case 8:            NumColors=256;   break; 
            case 24:           NumColors=0;     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==24)
     {
         for ( i=(bi.biHeight)-1;i>=0;i--) 
                Imgdata[i]=new unsigned char[bi.biWidth*3]; //每个数组元素也是一个指针数组

         for ( i=(bi.biHeight)-1;i>=0;i--) 
                for(j=0;j<bi.biWidth*3;j++) 
                  fread(&Imgdata[i][j],1,1,fp);//每次只读取一个1字节，存入数组
      } 
     else 
     {
         for ( i=(bi.biHeight)-1;i>=0;i--) 
             Imgdata[i]=new unsigned char[bi.biWidth]; 

         for ( i=(bi.biHeight)-1;i>=0;i--) 
             for(j=0;j<bi.biWidth;j++) 
                   fread(&Imgdata[i][j],1,1,fp);
     }

     fclose(fp);
}
 
void org(char *filename)
{
     FILE* fp;
     fp=fopen(filename,"wb"); 
     fwrite(&bf,sizeof(BITMAPFILEHEADER),1,fp); //写文件头 
     fwrite(&bi,sizeof(BITMAPINFOHEADER),1,fp); //写信息头 
     fwrite(ipRGB,sizeof(RGBQUAD),NumColors,fp);//写颜色头 

     if(bi.biBitCount==24)
         for (i=(bi.biHeight)-1 ;i>=0;i--) 
              for (j=0 ;j<my(bi.biWidth*3);j++) 
                  fwrite(&Imgdata[i][j],1,1,fp);
     else
         for (i=(bi.biHeight)-1 ;i>=0;i--) 
             for (j=0 ;j<bi.biWidth;j++)
                    fwrite(&Imgdata[i][j],1,1,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),1,fp); //写文件头 
     fwrite(&bi,sizeof(BITMAPINFOHEADER),1,fp); //写信息头 
     fwrite(ipRGB,sizeof(RGBQUAD),NumColors,fp);//写颜色头 

     char temp;
     for (i=(bi.biHeight)-1 ;i>=0;i--) 
         for (j=0 ;j<bi.biWidth*3;j++) 
             if(j%3==0)
             {
                       temp=(Imgdata[i][j]*76+Imgdata[i][j+1]*151+Imgdata[i][j+2]*28)>>8;
                       fwrite(&temp,1,1,fp);
             }
             else
             {
                       fwrite(&temp,1,1,fp);
             }
     fclose(fp);
 }
 
void display()
{
    printf("tagBITMAPFILEHEADER info is: %d
",sizeof(BITMAPFILEHEADER));
    printf("bfType              is %d.
", bf.bfType);
    printf("bfSize              is %d.
", bf.bfSize);
    printf("bfReserved1         is %d.
", bf.bfReserved1);
    printf("bfReserved2         is %d.
", bf.bfReserved2);
    printf("bfOffBits           is %d.
", bf.bfOffBits);

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