如何在iOS中从MTKView生成屏幕快照图像？

我在

ios9.1

中引用并通过

MetalKit

制作模型查看器应用程序

我想从

MTKView

制作屏幕快照图像（RGBA格式）。 但是，我只有黑色的图像

我该怎么办

谢谢你的阅读

代码：

自我解决

我发现了一个类似的例子

我为以下几点编写代码

1：使用Objective-C

2：不使用扩展MTLTexture

- (IBAction)onCapture:(id)sender
{
    id<MTLTexture> lastDrawableDisplayed = [metalView.currentDrawable texture];

    int width = (int)[lastDrawableDisplayed width];
    int height = (int)[lastDrawableDisplayed height];
    int rowBytes = width * 4;
    int selfturesize = width * height * 4;

    void *p = malloc(selfturesize);

    [lastDrawableDisplayed getBytes:p bytesPerRow:rowBytes fromRegion:MTLRegionMake2D(0, 0, width, height) mipmapLevel:0];

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Little | kCGImageAlphaFirst;

    CGDataProviderRef provider = CGDataProviderCreateWithData(nil, p, selfturesize, nil);
    CGImageRef cgImageRef = CGImageCreate(width, height, 8, 32, rowBytes, colorSpace, bitmapInfo, provider, nil, true, (CGColorRenderingIntent)kCGRenderingIntentDefault);

    UIImage *getImage = [UIImage imageWithCGImage:cgImageRef];
    CFRelease(cgImageRef);
    free(p);

    NSData *pngData = UIImagePNGRepresentation(getImage);
    UIImage *pngImage = [UIImage imageWithData:pngData];
    UIImageWriteToSavedPhotosAlbum(pngImage, self,
        @selector(completeSavedImage:didFinishSavingWithError:contextInfo:), nil);
}

此错误已在以下修复中修复。 所以，我更改了MTKView的设置

metalView.framebufferOnly = false;

谢谢。

请参阅：

对于swift 4.0

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
    }
}

---

self.mtkView.framebufferOnly=否

- (UIImage *)imageWithCurrentTexture:(MTKView *)mtkView {
     CIContext * context = [CIContext contextWithMTLDevice:mtkView.device];
     CIImage *outputImage = [[CIImage alloc] initWithMTLTexture:mtkView.currentDrawable.texture options:@{kCIImageColorSpace:(__bridge_transfer id)CGColorSpaceCreateDeviceRGB()}];
     CGImageRef cgImg = [context createCGImage:outputImage fromRect:CGRectMake(0, 0, [UIScreen mainScreen].nativeBounds.size.width, [UIScreen mainScreen].nativeBounds.size.height)];
     UIImage *resultImg = [UIImage imageWithCGImage:cgImg scale:1.0 orientation:UIImageOrientationDownMirrored];
     CGImageRelease(cgImg);
     return resultImg;
}

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
    }
}

- (UIImage *)imageWithCurrentTexture:(MTKView *)mtkView {
     CIContext * context = [CIContext contextWithMTLDevice:mtkView.device];
     CIImage *outputImage = [[CIImage alloc] initWithMTLTexture:mtkView.currentDrawable.texture options:@{kCIImageColorSpace:(__bridge_transfer id)CGColorSpaceCreateDeviceRGB()}];
     CGImageRef cgImg = [context createCGImage:outputImage fromRect:CGRectMake(0, 0, [UIScreen mainScreen].nativeBounds.size.width, [UIScreen mainScreen].nativeBounds.size.height)];
     UIImage *resultImg = [UIImage imageWithCGImage:cgImg scale:1.0 orientation:UIImageOrientationDownMirrored];
     CGImageRelease(cgImg);
     return resultImg;
}