You can use
libgd for portable handling of images.
For an example, here is how I capture screenshots in Dega:
#include <gd.h>
static void CreatePNG(const char* beauty_fn)
{
FILE*fp = fopen(beauty_fn, "wb");
if(!fp) { perror(beauty_fn); return; }
// xbuf, width, height
gdImagePtr im = gdImageCreateTrueColor(width,height);
for(unsigned y=0; y<height; ++y)
for(unsigned x=0; x<width; ++x)
{
const unsigned char* pixptr = &xbuf[(x + y * width)*3];
unsigned rr = pixptr[2];
unsigned gg = pixptr[1];
unsigned bb = pixptr[0];
gdImageSetPixel(im, x,y, (rr<<16)|(gg<<8)|(bb<<0));
}
gdImagePng(im, fp);
gdImageDestroy(im);
fclose(fp);
}
xbuf is here a pointer to the image rendered by the emulator; it is an array of 3-byte (BGR) pixels ordered from left to right, up to down.
