How to compensate the flipped coordinate system of core graphics for easy drawing?

Question

It\'s really a pain, but always when I draw an UIImage in -drawRect:, it\'s upside-down.

When I flip the coordinates, the image draws correctly, but at the cost of a

Answer 1

The better answer to this problem is to use the UIImage method drawInRect: to draw your image. I'm assuming you want the image to span the entire bounds of your view. This is what you'd type in your drawRect: method.

Instead of:

CGContextRef ctx = UIGraphicsGetCurrentContext();  
UIImage *myImage = [UIImage imageNamed:@"theImage.png"];  
CGImageRef img = [myImage CGImage];
CGRect bounds = [self bounds];
CGContextDrawImage(ctx, bounds, img);

Write this:

UIImage *myImage = [UIImage imageNamed:@"theImage.png"];
CGRect bounds = [self bounds];
[myImage drawInRect:bounds];