Antialiasing edges of UIView after transformation using CALayer's transform

Question

I have a UIView object that rotates using CALayer's transform:

// Create uiview object. UIImageView *block = [[UIImageView alloc] initWithFrame....]  // Apply rotation. CATransform3D basicTrans = CATransform3DIdentity; basicTrans.m34 = 1.0/-distance; blockImage.layer.transform = CATransform3DRotate(basicTrans, rangle, 1.0f, 0.0f, 0.0f); 

After rotating the edges of the object are not antialiasing. I need to antialias them. Help me, please. How can it be done?

Answer 1

One way to do this is by placing the image inside another view that's 5 pixels bigger. The bigger view should have a transparent rasterized border that will smooth the edges of the UIImageView:

view.layer.borderWidth = 3;  view.layer.borderColor = [UIColor clearColor].CGColor;  view.layer.shouldRasterize = YES;  view.layer.rasterizationScale = [[UIScreen mainScreen] scale]; 

Then, place your UIImageView inside this parent view and center it (With 2.5 pixels around each edge).

Finally, rotate the parent view instead of the image view.

It works very well - you can also encapsulate the whole thing in class that creates the hierarchy.