How to transform UIView's bounds space like GL space?

I'm handling UITouch event sourced from UIView. The problem is the coordinates are specified in UIView's bounds, left-top corner originated point space. But my GL viewport is defined in left-bottom originated (Y-flipped), pixel space.

I can convert all touch coordinates manually, however, if I could set custom transform on coordinate system of UIView, this will be solved automatically. Is this possible? What I want to do ultimat开发者_运维百科ely is receiving UITouch with my custom coordinate system.

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Use an affine transform:

CGAffineTransform transform = CGAffineTransformMakeScale(1.0, -1.0);

view.transform = transform;