How to render to offscreen bitmap then blit to screen using Core Graphics

Question

I would like to render to an offscreen bitmap (or array of RGBA values) and then blit those to a UIView during in the view\'s drawRect function. I

Answer 1

To render into an offscreen context and save it as a CGImageRef:

void *bitmapData = calloc(height, bytesPerLine);
CGContextRef offscreen = CGBitmapContextCreate(..., bitmapData, ...)
// draw stuff into offscreen
CGImageRef image = CGBitmapContextCreateImage(offscreen);
CFRelease(offscreen);
free(bitmapData);

To draw it on the screen:

- (void)drawRect:(CGRect)rect {
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextDrawImage(context, rect, image);
}

You could also just save the image in the view's layer's contents property (view.layer.contents = image), or use a UIImageView.