Question

In my app I have one root layer, and many images which are sublayers of rootLayer. I’d like to flatten all the sublayers of rootLayer into one layer/image, that don’t have any sublayers. I think I should do this by drawing all sublayers in core graphics context, but I don’t know how to do that.

I hope you’ll understand me, and sorry for my English.

Answer 1

From your own example for Mac OS X:

CGContextRef myBitmapContext = MyCreateBitmapContext(800,600);
[rootLayer renderInContext:myBitmapContext];
CGImageRef myImage = CGBitmapContextCreateImage(myBitmapContext);
rootLayer.contents = (id) myImage;
rootLayer.sublayers = nil;
CGImageRelease(myImage);

iOS:

UIGraphicsBeginImageContextWithOptions(rootLayer.bounds.size, NO, 0.0);
[rootLayer renderInContext: UIGraphicsGetCurrentContext()];
UIImage *layerImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
rootLayer.contents = (id) layerImage.CGImage;
rootLayer.sublayers = nil;

Also note the caveat in the docs:

The Mac OS X v10.5 implementation of
this method does not support the
entire Core Animation composition
model. QCCompositionLayer,
CAOpenGLLayer, and QTMovieLayer layers
are not rendered. Additionally, layers
that use 3D transforms are not
rendered, nor are layers that specify
backgroundFilters, filters,
compositingFilter, or a mask values.