The antialias of rotated CGImage/CGlayer seems jaggy, UIImageView's is not

Question

I need to mask a "texture" image with a rotated greyscale image.

I found out, that I have to do it with CGImages or CGlayers (if there is a simplier way using UIImageViews only, please let me know about it).

My problem is simple:

The antialias of any rotation-transformed CG stuff is quiet jaggy...

... but the antialias of a rotation-transformed UIImageView is kinda perfect. How can I produce that beautiful antialiased rotations?

I've uploaded a "proof" involving actual iPhone Simulator screenshots, to see what am I talkin' about: http://gotoandplay.freeblog.hu/files/Proof.png

I've tried to use CGImages, CGLayers, UIImageViews "captured" with renderInContext, I've tried to CGContextSetInterpolationQuality to high, and also tried to set CGContextSetAllowsAntialiasing - CGContextSetShouldAntialias, but every case returned the same jaggy result.

I'm planning to learn using OpenGL next year, but this development should released using CoreGraphics only. Please let me know how to get a perfectly rendered rotated image, I just can't accept it's impossible.

Answer 1

Have you tried adding a clear, 1 pixel border around your image? I've heard of that recommended as a trick to avoid aliasing, by giving CoreGraphics some room to work with when blending the edges.