save BMP file

BMP  header 有54 byte

memory 擺放的順序為 由下至上, 由左至右
pixel 順序為 B ,G, R  而不是  RGB
每個 pixel 所佔的size 可以設定成 4 byte or 3 byte

BMP 有個限制, 每個 row 所佔的  memory  byte數必須是  4 的倍數
為了簡化 這個   alignment 的問題 所以下面的範例選用 每個pixel佔據 4個byte

目前只完成 把mono image 轉成RGB,






//verifed
void WriteMonoImg2BMP(char* filename,double* buffer ,int img_width, int img_height,double div)
{

unsigned int width=img_width, height=img_height;
unsigned int datlen=img_width*img_height;
unsigned int file_size ;
unsigned int rgb_raw_data_offset=54;
unsigned char *pBmpBuffer;
int  pixel_bytes=4;
int  databytes;

int i;


string str1,str2;
int found;

str1=filename;
found=str1.find_last_of("/\\");
str2=str1.substr(0,found+1);

CreateDir((char*)str2.c_str());



databytes=width*height*pixel_bytes;
pBmpBuffer= new unsigned char[databytes];

unsigned char header[54] = {
  0x42, // identity : B
  0x4d, // identity : M
  0, 0, 0, 0, // file size
  0, 0, // reserved1
  0, 0, // reserved2
  54, 0, 0, 0, // RGB data offset
  40, 0, 0, 0, // struct BITMAPINFOHEADER size
  0, 0, 0, 0, // bmp width
  0, 0, 0, 0, // bmp height
  1, 0, // planes
  32, 0, // bit per pixel
  0, 0, 0, 0, // compression
  0, 0, 0, 0, // data size
  0, 0, 0, 0, // h resolution
  0, 0, 0, 0, // v resolution
  0, 0, 0, 0, // used colors
  0, 0, 0, 0 // important colors
};





// file size
file_size = width * height * 4 + rgb_raw_data_offset;
header[2] = (unsigned char)(file_size & 0x000000ff);
header[3] = (file_size >> 8)  & 0x000000ff;
header[4] = (file_size >> 16) & 0x000000ff;
header[5] = (file_size >> 24) & 0x000000ff;

// width
header[18] = width & 0x000000ff;
header[19] = (width >> 8) & 0x000000ff;
header[20] = (width >> 16) & 0x000000ff;
header[21] = (width >> 24) & 0x000000ff;

// height
header[22] = height &0x000000ff;
header[23] = (height >> 8)  & 0x000000ff;
header[24] = (height >> 16) & 0x000000ff;
header[25] = (height >> 24) & 0x000000ff;




  // because bmp layout is from bottom to top ,
  // need upside down image
int j, x,y,t,s;
double a;
unsigned char temp;
for(i=0;i<height;i++)
{

for(j=0;j<width;j++)
{
t=((i*width)+j)*pixel_bytes;
y=height-i-1;
x=j;
s= (y*width+x);

a= (buffer[s]/div);
a= a>255.0? 255.0 : a;
a= a<0.0 ? 0: a;
temp=(unsigned char)floor(a);
pBmpBuffer[t+0]=temp; //B
pBmpBuffer[t+1]=temp;  //G
pBmpBuffer[t+2]=temp;  //R
pBmpBuffer[t+3]=0;


}
}



ofstream  fout;
fout.open(filename,ios_base::out|ios_base::binary|ios_base::trunc);
fout.write ((char*)header, 54);
fout.write ((char*)pBmpBuffer, databytes);

fout.close();



/
*/

}