C語言實現BMP圖像處理(彩色圖轉灰度圖)

#include<stdio.h>
#include<windows.h>
 
int main(int argc, char* argv[])
{
 int bmpHeight;
 int bmpWidth;
 unsigned char *pBmpBuf;
 RGBQUAD *pColorTable;
 int biBitCount;
 
 //讀取bmp文件
 FILE *fp = fopen("./02.bmp", "rb");
 if (fp == 0)
  return 0;
 fseek(fp, sizeof(BITMAPFILEHEADER), 0);
 
 BITMAPINFOHEADER head;
 fread(&head, 40, 1, fp);
 bmpHeight = head.biHeight;
 bmpWidth = head.biWidth;
 biBitCount = head.biBitCount;
 
 fseek(fp, sizeof(RGBQUAD), 1);
 
 int LineByte = (bmpWidth*biBitCount / 8 + 3) / 4 * 4;//保證每一行字節數都為4的整數倍
 pBmpBuf = new unsigned char[LineByte*bmpHeight];
 fread(pBmpBuf, LineByte*bmpHeight, 1, fp);
 fclose(fp);
 
 //將24位真彩圖灰度化並保存
 FILE *fp1 = fopen("gray.bmp", "wb");
 if (fp1 == 0)
  return 0;
 int LineByte1 = (bmpWidth * 8 / 8 + 3) / 4 * 4;
 
 //修改文件頭,其中有兩項需要修改，分別為bfSize和bfOffBits
 BITMAPFILEHEADER bfhead;
 bfhead.bfType = 0x4D42;
 bfhead.bfSize = 14 + 40 + 256 * sizeof(RGBQUAD)+LineByte1*bmpHeight;//修改文件大小
 bfhead.bfReserved1 = 0;
 bfhead.bfReserved2 = 0;
 bfhead.bfOffBits = 14 + 40 + 256 * sizeof(RGBQUAD);//修改偏移字節數
 fwrite(&bfhead, 14, 1, fp1);    //將修改後的文件頭存入fp1；
 
 //修改信息頭，其中有兩項需要修改，1個位biBitCount:真彩圖為24 ，應改成8；另一個是biSizeImage:由於每像素所占位數的變化，所以位圖數據的大小發生變化
 BITMAPINFOHEADER head1;
 head1.biBitCount = 8;    //將每像素的位數改為8
 head1.biClrImportant = 0;
 head1.biCompression = 0;
 head1.biClrUsed = 0;
 head1.biHeight = bmpHeight;
 head1.biWidth = bmpWidth;
 head1.biPlanes = 1;
 head1.biSize = 40;
 head1.biSizeImage = LineByte1*bmpHeight;//修改位圖數據的大小
 head1.biXPelsPerMeter = 0;
 head1.biYPelsPerMeter = 0;
 fwrite(&head1, 40, 1, fp1);  //將修改後的信息頭存入fp1;
 
 pColorTable = new RGBQUAD[256];
 for (int i = 0; i < 256; i++){
  pColorTable[i].rgbRed = i;
  pColorTable[i].rgbGreen = i;
  pColorTable[i].rgbBlue = i; //是顏色表裡的B、G、R分量都相等，且等於索引值
 }
 fwrite(pColorTable, sizeof(RGBQUAD), 256, fp1); //將顏色表寫入fp1;
 
 //寫位圖數據
 unsigned char *pBmpBuf1;
 pBmpBuf1 = new unsigned char[LineByte1*bmpHeight];
 for (int i = 0; i < bmpHeight; i++){
  for (int j = 0; j<bmpWidth; j++){
   unsigned char *pb1, *pb2;
   pb1 = pBmpBuf + i*LineByte + j * 3;
   int y = *(pb1)*0.299 + *(pb1 + 1)*0.587 + *(pb1 + 2)*0.114;   //將每一個像素都按公式y=B*0.299+G*0.587+R*0.114進行轉化
   pb2 = pBmpBuf1 + i*LineByte1 + j;
   *pb2 = y;
  }
 }
 fwrite(pBmpBuf1, LineByte1*bmpHeight, 1, fp1);
 
 fclose(fp1);
 
 system("pause");
 return 0;
}