在 swift 中使用 Metal 拍摄当前屏幕的快照

Question

我试过了：

let scale = UIScreen.mainScreen().scale        
UIGraphicsBeginImageContextWithOptions(metalLayer.bounds.size, false, scale)
            
// metalLayer.renderInContext(UIGraphicsGetCurrentContext()!)

// self.view.layer ...

metalLayer.presentationLayer()!.renderInContext(UIGraphicsGetCurrentContext()!)
            
let image = UIGraphicsGetImageFromCurrentImageContext()           
UIGraphicsEndImageContext()
UIImageWriteToSavedPhotosAlbum(image, nil, nil, nil)

但结果是一个空的屏幕截图。任何帮助都会很好！

请记住，我想为CAMetalLayer 拍摄快照。

Answer 1

要截屏，需要获取帧缓冲区的MTLTexture。

1.如果你使用MTKView：

let texture = view.currentDrawable!.texture

2。如果你不使用MTKView

这就是我要做的——我会有一个属性来保存最后一个呈现在屏幕上的可绘制对象：

let lastDrawableDisplayed: CAMetalDrawable?

然后当你在屏幕上展示drawable时，我会更新它：

let commandBuffer = commandQueue.commandBuffer()
commandBuffer.addCompletedHandler { buffer in
  self.lastDrawableDisplayed = drawable
}

现在你只要需要截图，就可以得到这样的纹理：

let texture = lastDrawableDisplayed.texture

好的，现在当您拥有MTLTexture 时，您可以将其转换为CGImage，然后再转换为UIImage 或NSImage。

这是 OS X 游乐场的代码（MetalKit.MTLTextureLoader 不适用于 iOS 游乐场），其中我将 MTLTexture 转换为 CGImage

为此，我在MTLTexture 上做了一个小扩展。

import Metal
import MetalKit
import Cocoa

let device = MTLCreateSystemDefaultDevice()!
let textureLoader = MTKTextureLoader(device: device)

let path = "path/to/your/image.jpg"
let data = NSData(contentsOfFile: path)!

let texture = try! textureLoader.newTextureWithData(data, options: nil)

extension MTLTexture {
  
  func bytes() -> UnsafeMutablePointer<Void> {
    let width = self.width
    let height = self.height
    let rowBytes = self.width * 4
    let p = malloc(width * height * 4)
    
    self.getBytes(p, bytesPerRow: rowBytes, fromRegion: MTLRegionMake2D(0, 0, width, height), mipmapLevel: 0)
    
    return p
  }
  
  func toImage() -> CGImage? {
    let p = bytes()
    
    let pColorSpace = CGColorSpaceCreateDeviceRGB()
    
    let rawBitmapInfo = CGImageAlphaInfo.NoneSkipFirst.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue
    let bitmapInfo:CGBitmapInfo = CGBitmapInfo(rawValue: rawBitmapInfo)
    
    let selftureSize = self.width * self.height * 4
    let rowBytes = self.width * 4
    let provider = CGDataProviderCreateWithData(nil, p, selftureSize, nil)
    let cgImageRef = CGImageCreate(self.width, self.height, 8, 32, rowBytes, pColorSpace, bitmapInfo, provider, nil, true, CGColorRenderingIntent.RenderingIntentDefault)!
    
    return cgImageRef
  }
}

if let imageRef = texture.toImage() {
  let image = NSImage(CGImage: imageRef, size: NSSize(width: texture.width, height: texture.height))
}

Answer 2

对于 Swift 4.0， 只是转换haawa提供的代码

let lastDrawableDisplayed = metalView?.currentDrawable?.texture

if let imageRef = lastDrawableDisplayed?.toImage() {
    let uiImage:UIImage = UIImage.init(cgImage: imageRef)
}

extension MTLTexture {

    func bytes() -> UnsafeMutableRawPointer {
        let width = self.width
        let height   = self.height
        let rowBytes = self.width * 4
        let p = malloc(width * height * 4)

        self.getBytes(p!, bytesPerRow: rowBytes, from: MTLRegionMake2D(0, 0, width, height), mipmapLevel: 0)

        return p!
    }

    func toImage() -> CGImage? {
        let p = bytes()

        let pColorSpace = CGColorSpaceCreateDeviceRGB()

        let rawBitmapInfo = CGImageAlphaInfo.noneSkipFirst.rawValue | CGBitmapInfo.byteOrder32Little.rawValue
        let bitmapInfo:CGBitmapInfo = CGBitmapInfo(rawValue: rawBitmapInfo)

        let selftureSize = self.width * self.height * 4
        let rowBytes = self.width * 4
        let releaseMaskImagePixelData: CGDataProviderReleaseDataCallback = { (info: UnsafeMutableRawPointer?, data: UnsafeRawPointer, size: Int) -> () in
            return
        }
        let provider = CGDataProvider(dataInfo: nil, data: p, size: selftureSize, releaseData: releaseMaskImagePixelData)
        let cgImageRef = CGImage(width: self.width, height: self.height, bitsPerComponent: 8, bitsPerPixel: 32, bytesPerRow: rowBytes, space: pColorSpace, bitmapInfo: bitmapInfo, provider: provider!, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)!

        return cgImageRef
    }
}

Answer 3

在 iPhone 6s 上使用 XCode 9.1 在 Swift 4 / Metal 2 中工作时，我没有得到公认的答案。因此，我使用了一种稍微不同的方法，假设 lastDrawableDisplayed 已按照接受的答案中的描述保存。快速而肮脏且没有任何异常处理：

let context = CIContext()
let texture = self.lastDrawableDisplayed!.texture
let cImg = CIImage(mtlTexture: texture, options: nil)!
let cgImg = context.createCGImage(cImg, from: cImg.extent)!
let uiImg = UIImage(cgImage: cgImg)

这是基于使用的CIImage Initializer的文档：

init(mtlTexture:options:) 使用金属纹理提供的数据初始化图像对象。

和CIImage Processing，它描述了如何使用CIContext创建CGImage：

CIContext() 创建[s] CIContext 对象（使用默认选项）[...] context.createCGImage 将输出图像渲染[s] 为您可以显示或保存到文件的 Core Graphics 图像。

希望对任何使用 Swift 4 的人有所帮助。

编辑：此外，我的项目中有多个覆盖CAMetalLayer，并希望将它们组合成一个UIImage。因此需要引用每一层的最后一个CAMetalDrawable 对象。在添加新层（因此用作nextDrawable() 的提供者）之前，我只需将lastDrawableDisplayed 添加到数组[CAMetalDrawable] 中。当“导出”图层时，我只需将所有 UIImages 随后写入基于位图的图形上下文中，并使用UIGraphicsGetImageFromCurrentImageContext() 获得最终图像。

编辑：如果您在定位方面遇到问题，请尝试以下操作：

let uiImg = UIImage(cgImage: cgImg, scale: 1.0, orientation: UIImageOrientation.downMirrored)

Answer 4

斯威夫特 4.2

extension MTLTexture {
    
    func bytes() -> UnsafeMutableRawPointer {
        let width = self.width
        let height   = self.height
        let rowBytes = self.width * 4
        let p = malloc(width * height * 4)
        
        self.getBytes(p!, bytesPerRow: rowBytes, from: MTLRegionMake2D(0, 0, width, height), mipmapLevel: 0)
        
        return p!
    }
    
    func toImage() -> CGImage? {
        let p = bytes()
        
        let pColorSpace = CGColorSpaceCreateDeviceRGB()
        
        let rawBitmapInfo = CGImageAlphaInfo.noneSkipFirst.rawValue | CGBitmapInfo.byteOrder32Little.rawValue
        let bitmapInfo:CGBitmapInfo = CGBitmapInfo(rawValue: rawBitmapInfo)
        
        let selftureSize = self.width * self.height * 4
        let rowBytes = self.width * 4
        let releaseMaskImagePixelData: CGDataProviderReleaseDataCallback = { (info: UnsafeMutableRawPointer?, data: UnsafeRawPointer, size: Int) -> () in
            return
        }
        let provider = CGDataProvider(dataInfo: nil, data: p, size: selftureSize, releaseData: releaseMaskImagePixelData)
        let cgImageRef = CGImage(width: self.width, height: self.height, bitsPerComponent: 8, bitsPerPixel: 32, bytesPerRow: rowBytes, space: pColorSpace, bitmapInfo: bitmapInfo, provider: provider!, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)!
        
        return cgImageRef
    }
}