是否可以在图形上下文中呈现AVCaptureVideoPreviewLayer？

Question

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作为子图层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.

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:

  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);
}

//这会渲染一切,除了预览图层,这是空白的.

[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？

需要明确的是: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,我无法使其发挥作用.

Answer 1

我喜欢@ Roma的使用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,这里是做什么的:

实现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

• 现在您已经拥有了UIImage,将其添加到新的UIView中.
• 将叠加层添加到顶部作为子视图.

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;
}

Answer 2

我可以建议你尝试 GPU Image。

https://github.com/BradLarson/GPUImage

它使用openGL，所以速度相当快。它可以处理来自相机的图片并向它们添加过滤器（有很多），包括边缘检测、运动检测等等

它类似于 OpenCV，但根据我自己的经验，GPU 图像更容易与您的项目连接，并且语言是 Objective-C。

如果您决定使用 box2d 进行物理处理，则可能会出现问题 - 也使用 openGl，您将需要花费一些时间，直到这 2 个框架停止战斗））