是否可以在图形上下文中呈现AVCaptureVideoPreviewLayer？ [英] Is it possible to render AVCaptureVideoPreviewLayer in a graphics context?

问题描述

这似乎是一项简单的任务，但它让我疯狂。 是否可以将包含AVCaptureVideoPreviewLayer的UIView转换为要保存的图像？我想创建一个增强现实叠加层，并有一个按钮将图片保存到相机胶卷。按住电源按钮+主页键可将屏幕截图捕获到相机胶卷，这意味着我的所有捕获逻辑都在工作，并且任务是可行的。但我似乎无法以编程方式使其工作。

This seems like a simple task, yet it is driving me nuts. Is it possible to convert a UIView containing AVCaptureVideoPreviewLayer as a sublayer into an image to be saved? I want to create an augmented reality overlay and have a button save the picture to the camera roll. Holding the power button + home key captures the screenshot to the camera roll, meaning that all of my capture logic is working, AND the task is possible. But I cannot seem to be able to make it work programmatically.

我正在使用AVCaptureVideoPreviewLayer捕捉相机图像的实时预览。我渲染图像的所有尝试都失败了：

I'm capturing a live preview of the camera's image using AVCaptureVideoPreviewLayer . All of my attempts to render the image fail:

  previewLayer = [AVCaptureVideoPreviewLayer layerWithSession:captureSession];
//start the session, etc...


//this saves a white screen
- (IBAction)saveOverlay:(id)sender {
    NSLog(@"saveOverlay");

    UIGraphicsBeginImageContext(appDelegate.window.bounds.size);
        UIGraphicsBeginImageContext(scrollView.frame.size);

    [previewLayer.presentationLayer renderInContext:UIGraphicsGetCurrentContext()];


//    [appDelegate.window.layer renderInContext:UIGraphicsGetCurrentContext()];

    UIImage *screenshot = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    UIImageWriteToSavedPhotosAlbum(screenshot, self, 
                                   @selector(image:didFinishSavingWithError:contextInfo:), nil);
}

//这会渲染所有内容，除了预览图层，这是空白的。

//this renders everything, EXCEPT for the preview layer, which is blank.

[appDelegate.window.layer renderInContext:UIGraphicsGetCurrentContext()];

我在某处读过这可能是由于iPhone的安全问题。这是真的吗？

I've read somewhere that this may be due to security issues of the iPhone. Is this true?

为了清楚起见：我不想保存相机的图像。我想保存叠加在另一个图像上的透明预览图层，从而创建透明度。但由于某种原因，我无法使其工作。

Just to be clear: I don't want to save the image for the camera. I want to save the transparent preview layer superimposed over another image, thus creating transparency. Yet for some reason I cannot make it work.

推荐答案

我喜欢@ Roma关于使用GPU Image的建议 - 很棒的主意。 。 。 。但是如果你想要一个纯粹的CocoaTouch方法，那么该做什么：

I like @Roma's suggestion of using GPU Image - great idea. . . . however if you want a pure CocoaTouch approach, here's what to do:

实施AVCaptureVideoDataOutputSampleBufferDelegate

- (void)captureOutput:(AVCaptureOutput *)captureOutput didOutputSampleBuffer:(CMSampleBufferRef)sampleBuffer
fromConnection:(AVCaptureConnection *)connection
{
    // Create a UIImage+Orientation from the sample buffer data
    if (_captureFrame)
    {
        [captureSession stopRunning];

        _captureFrame = NO;
        UIImage *image = [ImageTools imageFromSampleBuffer:sampleBuffer];
        image = [image rotate:UIImageOrientationRight];

        _frameCaptured = YES;

        if (delegate != nil)
        {
            [delegate cameraPictureTaken:image];
        }
    }
}

捕获如下：

+ (UIImage *) imageFromSampleBuffer:(CMSampleBufferRef) sampleBuffer 
{
    // Get a CMSampleBuffer's Core Video image buffer for the media data
    CVImageBufferRef imageBuffer = CMSampleBufferGetImageBuffer(sampleBuffer); 
    // Lock the base address of the pixel buffer
    CVPixelBufferLockBaseAddress(imageBuffer, 0); 

    // Get the number of bytes per row for the pixel buffer
    void *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer); 

    // Get the number of bytes per row for the pixel buffer
    size_t bytesPerRow = CVPixelBufferGetBytesPerRow(imageBuffer); 
    // Get the pixel buffer width and height
    size_t width = CVPixelBufferGetWidth(imageBuffer); 
    size_t height = CVPixelBufferGetHeight(imageBuffer); 

    // Create a device-dependent RGB color space
    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); 

    // Create a bitmap graphics context with the sample buffer data
    CGContextRef context = CGBitmapContextCreate(baseAddress, width, height, 8, 
                                             bytesPerRow, colorSpace, kCGBitmapByteOrder32Little | kCGImageAlphaPremultipliedFirst); 
    // Create a Quartz image from the pixel data in the bitmap graphics context
    CGImageRef quartzImage = CGBitmapContextCreateImage(context); 
    // Unlock the pixel buffer
    CVPixelBufferUnlockBaseAddress(imageBuffer,0);

    // Free up the context and color space
    CGContextRelease(context); 
    CGColorSpaceRelease(colorSpace);

    // Create an image object from the Quartz image
    UIImage *image = [UIImage imageWithCGImage:quartzImage];

    // Release the Quartz image
    CGImageRelease(quartzImage);

    return (image);
}

将UIImage与叠加层混合

• 现在您已经拥有UIImage，将其添加到新的UIView中。


• 在顶部添加叠加层作为子视图。

捕获新的UIView

+ (UIImage*)imageWithView:(UIView*)view
{
    UIGraphicsBeginImageContextWithOptions(view.bounds.size, view.opaque, [UIScreen    mainScreen].scale);
    [view.layer renderInContext:UIGraphicsGetCurrentContext()];
    UIImage* img = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();
    return img;
}

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