将UIView内容呈现到MTLTexture中

Question

我有一个(动画的) UIView-Hierarchy，我想定期将UIView内容呈现到MTLTexture中以便进一步处理。

我尝试的是继承父UIView的子类，并

override public class var layerClass: Swift.AnyClass {
  return CAMetalLayer.self
}

但是来自nextDrawable()的纹理是黑色的，并且不显示视图内容。

你知道如何获取包含视图内容的MTLTexture吗？

Answer 1

感谢Matthijs Hollemanns用一些代码给我指明了正确的方向，我想出了下面的UIView扩展，它在全屏幕分辨率的iPhone8plus上每帧大约12毫秒就能完成这项工作。

extension UIView {

   func takeTextureSnapshot(device: MTLDevice) -> MTLTexture? {
      let width = Int(bounds.width)
      let height = Int(bounds.height)

      if let context = CGContext(data: nil,
                                 width: width,
                                 height: height,
                                 bitsPerComponent: 8,
                                 bytesPerRow: 0,
                                 space: CGColorSpaceCreateDeviceRGB(),
                                 bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue),
        let data = context.data {

        layer.render(in: context)

        let desc = MTLTextureDescriptor.texture2DDescriptor(pixelFormat: .rgba8Unorm,
                                                            width: width,
                                                            height: height,
                                                            mipmapped: false)
        if let texture = device.makeTexture(descriptor: desc) {
          texture.replace(region: MTLRegionMake2D(0, 0, width, height),
                          mipmapLevel: 0,
                          withBytes: data,
                          bytesPerRow: context.bytesPerRow)
          return texture
        }
      }
      return nil
    }
}