切割图片

/*只适用于WINDOWS BMP格式 真彩*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>


#define BMPFILETYPE (0x4D42)

#pragma pack(push,2)

/**
***定义文件头14字节.以2字节对齐
**/
typedef struct _tagBMPFILE
{
  unsigned short int bfType; //文件类型恒为"BM"==0x4D42 
  unsigned int bfSize; //文件大小,包括本结构 
  unsigned short int bfReserved1; //保留位1 
  unsigned short int bfReserved2; //保留位2 
  unsigned int bfOffsetBits; //到像素矩阵的偏移. 
}BMPFILE,*LPBMPFILE;


/**
***定义信息头40字节.以2字节对齐
**/
typedef struct _tagBMPINFOHEADER
{
  unsigned int biSize; //本结构大小 恒为40字节 
  int biWidth; //DIB宽度 像素为单位 
  int biHeight; //DIB高度 像素为单位 
  unsigned short int biPlanes; //不用理会..恒为1 
  unsigned short int biBitCount; //颜色深度 
  unsigned int biCompression; //是否压缩 
  unsigned int biSizeImage; //DIB总大小 每行四字节对齐后算的
  int biXPelsPerMeter; //水平分辨率 像素每米 
  int biYPelsPerMeter; //竖直分辨率 像素每米 
  unsigned int biClrUsed; //已用颜色数 
  unsigned int biClrImportant; //重要颜色数 
}BMPINFOHEADER,*LPBMPINFOHEADER;



#pragma pack(pop)


typedef void * LPDIB;


//用于补齐行边界.返回的是字节数 4的整数倍 
#define ROWWIDTH(bits) ((((bits)+31)&~31)>>3)




int xxx(const char *fName, const char *fOut1, const char *fOut2)
{
  int i;
  FILE *fp;
  FILE *pic1, *pic2;
  int h1, h2;
  int nRowPix;
  int nRowWidth;
  BMPFILE l_bmpFile;
  BMPINFOHEADER l_bmpInfo;
  unsigned char *buff;
   
  if (fName == NULL || strlen(fName) == 0)
  {
  return -1;
  }
   
  if ((fp = fopen(fName, "rb")) == NULL)
  {
  perror("fopen");
  return -1;
  }
   
  memset(&l_bmpFile, 0, sizeof(BMPFILE));
  if (fread(&l_bmpFile, sizeof(BMPFILE), 1, fp) < 1)
  {
  perror("fread");
  goto err_exit;
  }
   
  if (l_bmpFile.bfType != BMPFILETYPE)
  {
  fprintf(stderr, "Not a bitmap file!/n");
  goto err_exit;
  }
   
  if (fread(&l_bmpInfo, sizeof(BMPINFOHEADER), 1, fp) < 1)
  {
  perror("fread");
  goto err_exit;
  }
   
  nRowPix = l_bmpInfo.biWidth * l_bmpInfo.biBitCount;
  nRowWidth = ROWWIDTH(nRowPix);
  if ((buff = (unsigned char *)malloc(nRowWidth)) == NULL)
  {
  goto err_exit;
  }
   
  h1 = l_bmpInfo.biHeight / 2;
  h2 = l_bmpInfo.biHeight - h1;
   
  /*下面不管错误了,文件很麻烦..上面代码都有.*/
   
  pic1 = fopen(fOut1, "wb");
  pic2 = fopen(fOut2, "wb");
   
  l_bmpFile.bfSize = sizeof(BMPFILE) + sizeof(BMPINFOHEADER) + h1 * nRowWidth;
  fwrite(&l_bmpFile, sizeof(BMPFILE), 1, pic1);
  l_bmpInfo.biHeight = h1;
  l_bmpInfo.biSizeImage = nRowWidth * h1;
  fwrite(&l_bmpInfo, sizeof(BMPINFOHEADER), 1, pic1);
  for (i = 0; i < h1; i ++)
  {
  fread(buff, nRowWidth, 1, fp);
  fwrite(buff, nRowWidth, 1, pic1);
  }
  fclose(pic1);
   
  l_bmpFile.bfSize = sizeof(BMPFILE) + sizeof(BMPINFOHEADER) + h2 * nRowWidth;
  fwrite(&l_bmpFile, sizeof(BMPFILE), 1, pic2);
  l_bmpInfo.biHeight = h2;
  l_bmpInfo.biSizeImage = nRowWidth * h2;
  fwrite(&l_bmpInfo, sizeof(BMPINFOHEADER), 1, pic2);
  for (i = 0; i < h2; i ++)
  {
  fread(buff, nRowWidth, 1, fp);
  fwrite(buff, nRowWidth, 1, pic2);
  }
  fclose(pic1);
   
  free(buff);
   
   
  fclose(fp);
  return 0;
   
err_exit:
  fclose(fp);
  return -1;
}


int main()
{
  xxx("test.bmp", "2.bmp", "1.bmp");
  return 0;
}