I am developing an iPad application. In my application users can move, rotate and scale images. I ve noticed that when I add a 3d shadowed border to the images, it makes them incredibly heavy and unresponsive. I add the border using this code:
self.layer.MasksToBounds = false;
self.layer.ShadowColor = [[UIColor alloc] initWithRed:0 green:0 blue:0 alpha:0.5].CGColor;
self.layer.ShadowOpacity = 1.0f;
self.layer.ShadowOffset = CGSizeMake(0, 2.5f);
为什么发生这种事?我有什么办法解决这个问题?
这是CaLayer 阴影的一个众所周知的问题。 设置 < code> shadowPath 属性, 您将会看到良好的性能提升 。
阴影路径只能是您图像视图的边框路径。 您应该能够设置它一次, 层变换会随着图像的缩放等不断更新 。
您也应设置
self.layer.ShouldRasterize = YES
这会将层分解。 如果设置为 NO( 默认), 所有在图层上应用的过滤器和阴影都会被重新计算好几次, 这需要相当大的性能。 特别是在滚动视图或表格视图中 。
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