Resize CGImageRef without anti-liasing

I am trying to resize a 10x10 pixel CGImageRef, captured like this:

CGImageRef imageRef = CGImageCreateWithImageInRect(scree开发者_如何学JAVAnShot, CGRectMake(mouseLoc.x-5, screen_height-mouseLoc.y-5, 10, 10));

CGContextRef mainViewContentContext = CGBitmapContextCreate (NULL, maskImage.size.width, maskImage.size.height, 8, maskImage.size.height*4, colorSpace, kCGImageAlphaPremultipliedFirst);

CGContextDrawImage(mainViewContentContext, NSMakeRect(0,0, maskImage.size.width, maskImage.size.height), imageRef);

Then I need to make a 250x250 pixel image like this this, but the upscaled image looks like there is anti aliasing on it (looks like this)

try CGContextSetInterpolationQuality:

// disable interpolation like this:
CGContextSetInterpolationQuality(mainViewContentContext, kCGInterpolationNone);
// now draw