I Have bad performance on using shadow effect

Question

I put some image views on scroll view. And when I drag this scroll view, I didn\'t have any problems.

But after I applied shadow effect to these image views, dragging th

Answer 1

See CALayer.shouldRasterize (iOS 3.2+, but so is shadowOffset/etc):

When the value of this property is YES, the layer is rendered as a bitmap in its local coordinate space and then composited to the destination with any other content. Shadow effects and any filters in the filters property are rasterized and included in the bitmap.

You probably also want to set rasterizationScale appropriately.