gistfile1.m

/*
Source: Apple Developer - Understanding iOS View Compositing
*/

- (void)drawLayer:(CALayer *)layer inContext:(CGContextRef)ctx {
	UIImage *image = [self loadImage];
	
	if (image != nil) {
		CGSize s = image.size;
		CGRect r = layer.bounds;
		CGFloat scale = MIN(r.size.width / s.width, r.size.height / s.height);
		s.width *= scale; s.height *= scale;
		r.origin.x += (r.size.width - s.width) * .5;
		r.size.width = s.width;
		r.origin.y += (r.size.height - s.height) * .5;
		r.size.height = s.height;
		
		CGContextSaveGState(ctx);
		CGContextDrawImage(ctx, r, image.CGImage);
		CGContextRestoreGState(ctx);
	}
}