使用硬件加速内容截取 WKWebview 的屏幕截图

我在截屏时遇到严重问题WKWebview内容当有硬件加速内容（一些在 iframe 内运行的特定赌场游戏）。 到目前为止，我使用了像大家建议的标准截图方式：

UIGraphicsBeginImageContextWithOptions(containerView.frame.size, true, 0.0)

containerView.layer.render(in: UIGraphicsGetCurrentContext()!)

//This line helps to fix view rendering for taking screenshot on older iOS devices
containerView.drawHierarchy(in: containerView.bounds, afterScreenUpdates: true)

let image = UIGraphicsGetImageFromCurrentImageContext()!

UIGraphicsEndImageContext()

在我在 WKWebview 中获取由 GPU 渲染的一些内容之前，此方法非常有效。 GPU 渲染的内容在屏幕截图上显示为黑色。我尝试了这种方法可以使用的所有技巧，但没有任何帮助。即使 XCode 视图层次结构调试器也无法显示硬件加速内容。因此，与Android类似，我需要另一种方式来截图. 我已经解决了 Android 上的类似问题，开始记录屏幕上发生的所有事情，并在获得第一张图像后停止屏幕记录。

我已经经历了许多 Stack Overflow 问题和解决方案，但它们大多都是 Obj-C（我完全不喜欢），已经过时或不够具体以满足我的需求。

现在我发现我可以使用glReadPixels直接从 OpenGL 读取像素（如果我的内容是硬件加速的，那么我可以从显卡读取这些像素是有意义的，对吧？）

到目前为止，我已经成功创建了一个 Swift 代码片段，可以执行类似的操作渲染缓冲区 -> 帧缓冲区 -> glReadPixels -> 图像

let width = Int(containerView.frame.size.width)
let height = Int(containerView.frame.size.height)

//BeginImageContext code was run above

let api = EAGLRenderingAPI.openGLES3
let context2 = EAGLContext(api: api)
EAGLContext.setCurrent(context2)

// Setup render buffer
var renderBuffer : GLuint = GLuint()

let size = GLsizei(10)
glGenRenderbuffers(size, &renderBuffer)
glBindRenderbuffer(GLenum(GL_RENDERBUFFER), renderBuffer)
let bufferWidth = GLsizei(width * 1)
let bufferHeight = GLsizei(height * 1)
let bufferFormat = GLenum(GL_RGBA8)
glRenderbufferStorage(GLenum(GL_RENDERBUFFER), bufferFormat, bufferWidth, bufferHeight)

// Setup frame buffer
var frameBuffer = GLuint()
glGenFramebuffers(GLsizei(10), &frameBuffer)
glBindFramebuffer(GLenum(GL_FRAMEBUFFER), frameBuffer)
glFramebufferRenderbuffer(GLenum(GL_FRAMEBUFFER), GLenum(GL_COLOR_ATTACHMENT0), GLenum(GL_RENDERBUFFER), renderBuffer)

// Draw
glReadBuffer(GLenum(GL_RENDERBUFFER))
glClearColor(0.1, 0.2, 0.3, 0.2)
glClear(GLbitfield(GL_COLOR_BUFFER_BIT))

//--------------
let bytes = malloc(width*height*4)
let bytes2 = malloc(width*height*4)

let x : GLint = GLint(0)
let y : GLint = GLint(0)
let w : GLsizei = GLsizei(width)
let h : GLsizei = GLsizei(height)

glReadPixels(x, y, w, h, GLenum(GL_RGBA), GLenum(GL_UNSIGNED_BYTE), bytes)

let data = NSData(bytes: bytes, length: width * height * 4)
let dataProvider = CGDataProvider(data: data)
//let dataProvider2 = CGDataProvider(dataInfo: nil, data: bytes!, size: width * height * 4, releaseData: )
let colorspace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo: CGBitmapInfo = [.byteOrder32Little, CGBitmapInfo(rawValue: CGImageAlphaInfo.last.rawValue)]
let aCGImage = CGImage(
    width: Int(width),
    height: Int(height),
    bitsPerComponent: 8,
    bitsPerPixel: 32,
    bytesPerRow: 4 * Int(width),
    space: colorspace,
    bitmapInfo: bitmapInfo,
    provider: dataProvider!,
    decode: nil, 
    shouldInterpolate: true,
    intent: .defaultIntent
    )!
let imaag = UIImage(cgImage: aCGImage)
//I get the image of the same color that is defined at clearColor

现在我的问题是，我走的路对吗？ 我是否可以以某种方式获取我的 WKWebview （或拍摄它的快照并将其放入 UIView 中）渲染缓冲区/帧缓冲区，以便glReadPixels 实际上会读取屏幕上有什么？

附言！我见过很多关于从 CAEAGLView 中获取 UIImage 的问题，但就我而言，它不是 CAEGLView，而是 WKWebview。 非常感激。

我有一个简单的方法来拍摄快照，有代码。

- (void)screenLoogShoot:(void (^)(UIImage *fullImage))snapShotHandler {
    WKWebView *webView = self.webView;
    UIScrollView *scrollView = webView.scrollView;
    CGFloat boundsWidth = scrollView.bounds.size.width;
    CGFloat contentHeight = scrollView.contentSize.height;
    CGFloat scale = [UIScreen mainScreen].scale;
    CGRect oldFrame = self.webView.frame;

    if (@available(iOS 11.0, *)) {
        self.webView.frame = CGRectMake(0, 0, boundsWidth, contentHeight);
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            WKSnapshotConfiguration *configuration = [WKSnapshotConfiguration new];
            configuration.rect = CGRectMake(0, 0, boundsWidth, contentHeight);
            configuration.snapshotWidth = @(boundsWidth);
            [self.webView takeSnapshotWithConfiguration:configuration completionHandler:^(UIImage * _Nullable snapshotImage, NSError * _Nullable error) {
                UIGraphicsBeginImageContextWithOptions(CGSizeMake(boundsWidth, contentHeight), NO, scale);
                [snapshotImage drawInRect:CGRectMake(0, 0, boundsWidth, contentHeight)]; 
                UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext();
                UIGraphicsEndImageContext();
                self.webView.frame = oldFrame;
                snapShotHandler(fullImage);
            }];
        });
    } else {
        self.webView.frame = CGRectMake(0, 0, boundsWidth, contentHeight);
        dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(0.3 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
            UIGraphicsBeginImageContextWithOptions(CGSizeMake(webView.bounds.size.width, webView.bounds.size.height), NO, scale);
            [webView drawViewHierarchyInRect:CGRectMake(0, 0, boundsWidth, contentHeight) afterScreenUpdates:YES];
            UIImage *fullImage = UIGraphicsGetImageFromCurrentImageContext();
            UIGraphicsEndImageContext();
            self.webView.frame = oldFrame;
            !snapShotHandler ? : snapShotHandler(fullImage);
        });
    }
}