Bit Blitting with CGLayer

cglayer_blit.m

- (void)drawRect:(NSRect)dirtyRect
{
	[super drawRect:dirtyRect];

	static int redOffset = 0;
	static int greenOffset = 0;
	static int blueOffset = 0;
	
	for (int y = 0; y < _bitmapHeight; y++)
	{
		for (int x = 0; x < _bitmapWidth; x++)
		{
			unsigned char* pixel = _pixels + (y * _bitmapWidth + x) * _bitmapComponents;
			pixel[0] = x + y + redOffset;  // red
			pixel[1] = y + greenOffset;
			pixel[2] = x + blueOffset;
			pixel[3] = x + y + redOffset;
		}
	}
	
	++redOffset;
	++greenOffset;
	++blueOffset;

	CGContextRef gctx = [[NSGraphicsContext currentContext] graphicsPort];
	CGRect layerRect = [self bounds];
	
	CGLayerRef layer = CGLayerCreateWithContext(gctx, layerRect.size, NULL);
	CGContextRef lctx = CGLayerGetContext(layer);
	
	CMProfileRef prof;
	CMGetSystemProfile(&prof);
	_colorSpace = CGColorSpaceCreateWithPlatformColorSpace(prof);
	CMCloseProfile(prof);

	_bitmapContext = CGBitmapContextCreate(_pixels, _bitmapWidth, _bitmapHeight,
						_bitmapBitsPerComponent, _bitmapBytesPerRow,
						_colorSpace, _bitmapInfo);
	_bitmapImageRef = CGBitmapContextCreateImage(_bitmapContext);

	CGContextSetInterpolationQuality(_bitmapContext, kCGInterpolationNone);

	CGContextDrawImage(lctx, layerRect, _bitmapImageRef);
	
	CGContextSaveGState(gctx);
	
	CGContextDrawLayerAtPoint(gctx, CGPointZero, layer);
	
	CGContextRestoreGState(gctx);
	
	CGColorSpaceRelease(_colorSpace);
	CGImageRelease(_bitmapImageRef);
	CGContextRelease(_bitmapContext);
	CGLayerRelease(layer);
}