gistfile1.txt

/* Upscale textures to user's requested minimum size.  This is a trick to make
 * filters look as good on low-res textures as on high-res ones, by making
 * low-res textures BECOME high-res ones.  This is helpful for worlds that
 * mix high- and low-res textures, or for mods with least-common-denominator
 * textures that don't have the resources to offer high-res alternatives.
 */
video::IImage *textureMinSizeUpscale(video::IVideoDriver *driver, video::IImage *orig) {
	if(orig == NULL)
		return orig;

	s32 scaleto = g_settings->getS32("texture_min_size");
	if (scaleto < 2)
		return orig;


	const core::dimension2d<u32> dim = orig->getDimension();

	// Don't upscale 1px images.  They don't benefit from it anyway
	// (wouldn't have been blurred) and MIGHT be sun/moon tonemaps.
	if (dim.Width <= 1 || dim.Height <= 1)
		return orig;

	/* Calculate scaling needed to make the shortest texture dimension
	 * equal to the target minimum.  If e.g. this is a vertical frames
	 * animation, the short dimension will be the real size.
	 */
	u32 xscale = scaleto / dim.Width;
	u32 yscale = scaleto / dim.Height;
	u32 scale = (xscale > yscale) ? xscale : yscale;

	// Never downscale; only scale up by 2x or more.
	if (scale > 1) {
		u32 w = scale * dim.Width;
		u32 h = scale * dim.Height;
		const core::dimension2d<u32> newdim = core::dimension2d<u32>(w, h);
		video::IImage *newimg = driver->createImage(
				orig->getColorFormat(), newdim);
		orig->copyToScaling(newimg);
		return newimg;
	}

	return orig;
}