Creating a BMP file (bitmap) in C

Question

I\'m trying to make a bitmap in C, just from code. I\'m currently trying to make a very easy .bmp image, with a height of 1px and a width of 4 pixels, with all white pixels.

Answer 1

Here is the code tested on linux.

#include 
#include 
#include 
#include 
#define _height 600
#define _width 800
#define _bitsperpixel 24
#define _planes 1
#define _compression 0
#define _pixelbytesize _height*_width*_bitsperpixel/8
#define _filesize _pixelbytesize+sizeof(bitmap)
#define _xpixelpermeter 0x130B //2835 , 72 DPI
#define _ypixelpermeter 0x130B //2835 , 72 DPI
#define pixel 0xFF
#pragma pack(push,1)
typedef struct{
    uint8_t signature[2];
    uint32_t filesize;
    uint32_t reserved;
    uint32_t fileoffset_to_pixelarray;
} fileheader;
typedef struct{
    uint32_t dibheadersize;
    uint32_t width;
    uint32_t height;
    uint16_t planes;
    uint16_t bitsperpixel;
    uint32_t compression;
    uint32_t imagesize;
    uint32_t ypixelpermeter;
    uint32_t xpixelpermeter;
    uint32_t numcolorspallette;
    uint32_t mostimpcolor;
} bitmapinfoheader;
typedef struct {
    fileheader fileheader;
    bitmapinfoheader bitmapinfoheader;
} bitmap;
#pragma pack(pop)

int main (int argc , char *argv[]) {
    FILE *fp = fopen("test.bmp","wb");
    bitmap *pbitmap  = (bitmap*)calloc(1,sizeof(bitmap));
    uint8_t *pixelbuffer = (uint8_t*)malloc(_pixelbytesize);
    strcpy(pbitmap->fileheader.signature,"BM");
    pbitmap->fileheader.filesize = _filesize;
    pbitmap->fileheader.fileoffset_to_pixelarray = sizeof(bitmap);
    pbitmap->bitmapinfoheader.dibheadersize =sizeof(bitmapinfoheader);
    pbitmap->bitmapinfoheader.width = _width;
    pbitmap->bitmapinfoheader.height = _height;
    pbitmap->bitmapinfoheader.planes = _planes;
    pbitmap->bitmapinfoheader.bitsperpixel = _bitsperpixel;
    pbitmap->bitmapinfoheader.compression = _compression;
    pbitmap->bitmapinfoheader.imagesize = _pixelbytesize;
    pbitmap->bitmapinfoheader.ypixelpermeter = _ypixelpermeter ;
    pbitmap->bitmapinfoheader.xpixelpermeter = _xpixelpermeter ;
    pbitmap->bitmapinfoheader.numcolorspallette = 0;
    fwrite (pbitmap, 1, sizeof(bitmap),fp);
    memset(pixelbuffer,pixel,_pixelbytesize);
    fwrite(pixelbuffer,1,_pixelbytesize,fp);
    fclose(fp);
    free(pbitmap);
    free(pixelbuffer);
}