Image appearing pixelerated - objective-c

Question

This is what I am trying to do
Create a UIImage View.
Do some drawing on it
Press a share button to share the image with the drawings on it.
My code works perfect on iPad and iPhone. Problem comes with retina display. So my guess is some scale is not handled correctly, but not sure what I am doing wrong. This is my code
// Create the UIImageView named centerCanvas
// Do the drawing
CGPoint origin = centerCanvas.frame.origin;
CGSize size = centerCanvas.frame.size;
CGSize screenSize = [self returnScreenSize];
CGRect rect = CGRectMake(origin.x, origin.y, size.width, size.height);
UIGraphicsBeginImageContext(screenSize);
CGContextRef context = UIGraphicsGetCurrentContext();
[self.view.layer renderInContext:context];
UIImage *img = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
CGImageRef imageRef = CGImageCreateWithImageInRect([img CGImage], rect);
[shareView setImage:[UIImage imageWithCGImage:imageRef]];
-(CGSize) returnScreenSize
{
CGRect screenBounds = [[UIScreen mainScreen] bounds];
CGFloat screenScale = [[UIScreen mainScreen] scale];
CGSize screenSize = CGSizeMake(screenBounds.size.width * screenScale,screenBounds.size.height * screenScale);
return screenSize;
}

Answer 1

Try using
UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, 0.0);
instead of the old UIGraphicsBeginImageContext, which uses a scale factor (third argument above) equal to 1. By giving 0.0 as a scale factor you get a scale factor for your current screen. Have a look at the reference.