BMPfile01(function)

// create a BMP file
// give a color to every pixels of the BMP file
// use function to simpligy the main function interface
#include <iostream>

using namespace std;

typedef struct{
    unsigned short int signature;
    unsigned int size;
    unsigned short int reserved[2];
    unsigned int offset;
}FileHeader;

void WriteFileHeader(FileHeader fh, FILE *fp) {
    fwrite(&fh.signature,sizeof(unsigned short int),1,fp);
    fwrite(&fh.size,sizeof(unsigned int),1,fp);
    fwrite(&fh.reserved,sizeof(unsigned short int),2,fp);
    fwrite(&fh.offset,sizeof(unsigned int),1,fp);
}

typedef struct{
    unsigned int headerSize;
    int width;
    int height;
    unsigned short int plane;
    unsigned short int bits;
    unsigned int compression;
    unsigned int imageSize;
    int xPixel;
    int yPixel;
    unsigned int colorTable;
    unsigned int colorCount;

}InfoHeader;

void WriteInfoHeader(InfoHeader info, FILE *fp){
    fwrite(&info.headerSize,sizeof(unsigned int),1,fp); // headerSize
    fwrite(&info.width,sizeof(int),1,fp);   // width
    fwrite(&info.height,sizeof(int),1,fp); // height
    fwrite(&info.plane,sizeof(unsigned short int),1,fp); // plane
    fwrite(&info.bits,sizeof(unsigned short int),1,fp); // bits
    fwrite(&info.compression,sizeof(unsigned int),1,fp); // compression
    fwrite(&info.imageSize,sizeof(unsigned int),1,fp);  // imageSize
    fwrite(&info.xPixel,sizeof(int),1,fp); // xPixel
    fwrite(&info.yPixel,sizeof(int),1,fp); // yPixel
    fwrite(&info.colorTable,sizeof(unsigned int),1,fp); // colorTable
    fwrite(&info.colorCount,sizeof(unsigned int),1,fp); // colorCount
}

int main(){

// create a bmp-format file
    int width = 1024, height = 1024;
    FileHeader fileHeader = {
        0x4d42, 54 + width * height * 4, {0, 0}, 54
    };
    InfoHeader infoHeader = {
        40, width, height, 1, 32, 0, 64, 4, 4, 4, 4
    };

    FILE *fp;
    fp = fopen("myBMP06.bmp","wb");
    // write fileHeader into the file
    WriteFileHeader(fileHeader,fp);
    // write infoHeader into the file
    WriteInfoHeader(infoHeader, fp);

// put color in the file
                        // BGRA
unsigned char color[4] = {222,125,125,50};
for (int i = 0; i < width; i++) {
    for (int j = 0; j < height; j++) {
        fwrite(color,sizeof(unsigned char),4,fp);
    }
}

    fclose(fp);
}