test.c

#include <stdio.h>
#include <string.h>
#include <stdlib.h>


int main()
{
    
    int w = 80;
    int h = 60;
    
    int r,g,b;
    
    double red[w][h];
    double green[w][h];
    double blue[w][h];
    
    unsigned char bmpfileheader[14] = {'B','M', 0,0,0,0, 0,0, 0,0, 54,0,0,0};
    unsigned char bmpinfoheader[40] = {40,0,0,0, 0,0,0,0, 0,0,0,0, 1,0, 24,0};
    unsigned char bmppad[3] = {0,0,0};

    int i = 0;
    int j = 0;
    int x = 0;
    int y = 0;
    int yres = 0;
    
    FILE *f;
    unsigned char *img = NULL;
    
    int filesize = 54 + 3*w*h;  //w is your image width, h is image height, both int
    /*
    if(img){
        free(img);
    }*/
    
    img = (unsigned char *)malloc(3*w*h);
    
    memset(img,0,sizeof(img));
    
    for(i=0; i<w; i++) {
        for(j=0; j<h; j++){
            red[i][j] = 0.0;
            blue[i][j] = 0.0;
            green[i][j] = 0.0;
        }
    }
    
    
    for(i=0; i<w; i++)
    {
        for(j=0; j<h; j++)
        {
            x=i; y=(yres-1)-j;
            r = red[i][j]*255;
            g = green[i][j]*255;
            b = blue[i][j]*255;
            if (r > 255) r=255;
            if (g > 255) g=255;
            if (b > 255) b=255;
            img[(x+y*w)*3+2] = (unsigned char)(r);
            img[(x+y*w)*3+1] = (unsigned char)(g);
            img[(x+y*w)*3+0] = (unsigned char)(b);
        }
    }
    
    bmpfileheader[ 2] = (unsigned char)(filesize    );
    bmpfileheader[ 3] = (unsigned char)(filesize>> 8);
    bmpfileheader[ 4] = (unsigned char)(filesize>>16);
    bmpfileheader[ 5] = (unsigned char)(filesize>>24);
    
    bmpinfoheader[ 4] = (unsigned char)(       w    );
    bmpinfoheader[ 5] = (unsigned char)(       w>> 8);
    bmpinfoheader[ 6] = (unsigned char)(       w>>16);
    bmpinfoheader[ 7] = (unsigned char)(       w>>24);
    bmpinfoheader[ 8] = (unsigned char)(       h    );
    bmpinfoheader[ 9] = (unsigned char)(       h>> 8);
    bmpinfoheader[10] = (unsigned char)(       h>>16);
    bmpinfoheader[11] = (unsigned char)(       h>>24);
    
    f = fopen("img.bmp","wb");
    fwrite(bmpfileheader,1,14,f);
    fwrite(bmpinfoheader,1,40,f);
    for(i=0; i<h; i++)
    {
        fwrite(img+(w*(h-i-1)*3),3,w,f);
        fwrite(bmppad,1,(4-(w*3)%4)%4,f);
    }
    fclose(f);
    
    return 0;
}