ios - AVFoundation 输出的图像仅占屏幕的 1/4

Question

我玩过AVFoundation尝试将过滤器应用于实时视频。我尝试将过滤器应用于 AVCaptureVideoDataOutput ，但输出只占 View 的 1/4。



这是我的一些相关代码

捕获

let availableCameraDevices = AVCaptureDevice.devicesWithMediaType(AVMediaTypeVideo)
    for device in availableCameraDevices as! [AVCaptureDevice] {
        if device.position == .Back {
            backCameraDevice = device
        } else if device.position == .Front {
            frontCameraDevice = device
        }
    }

配置输出

private func configureVideoOutput() {
    videoOutput = AVCaptureVideoDataOutput()
    videoOutput?.setSampleBufferDelegate(self, queue: dispatch_queue_create("sample buffer delegate", DISPATCH_QUEUE_SERIAL))
    if session.canAddOutput(videoOutput) {
        session.addOutput(videoOutput)
    }
}

获取图像

func captureOutput(captureOutput: AVCaptureOutput!, didOutputSampleBuffer sampleBuffer:
    CMSampleBuffer!, fromConnection connection: AVCaptureConnection!) {
    // Grab the pixelbuffer
    let pixelBuffer = CMSampleBufferGetImageBuffer(sampleBuffer)!

    // create a CIImage from it, rotate it, and zero the origin
    var image = CIImage(CVPixelBuffer: pixelBuffer)
    image = image.imageByApplyingTransform(CGAffineTransformMakeRotation(CGFloat(-M_PI_2)))
    let origin = image.extent.origin
    image = image.imageByApplyingTransform(CGAffineTransformMakeTranslation(-origin.x, -origin.y))


    self.manualDelegate?.cameraController(self, didOutputImage: image)
}

使成为

func cameraController(cameraController: CameraController, didOutputImage image: CIImage) {
    if glContext != EAGLContext.currentContext() {
        EAGLContext.setCurrentContext(glContext)
    }

    let filteredImage = image.imageByApplyingFilter("CIColorControls", withInputParameters: [kCIInputSaturationKey: 0.0])

    var rect = view.bounds

    glView.bindDrawable()
    ciContext.drawImage(filteredImage, inRect: rect, fromRect: image.extent)
    glView.display()
}

我预计视网膜显示和比例因子会导致这种情况，但不知道我应该在哪里处理这个问题。我已经将内容比例因子设置为 GLKView，但没有运气。

private var glView: GLKView {
    // Set in storyboard
    return view as! GLKView
}

glView.contentScaleFactor = glView.bounds.size.width / UIScreen.mainScreen().bounds.size.width * UIScreen.mainScreen().scale

Answer 1

您的问题在于输出 rect用于drawImage功能:

ciContext.drawImage(filteredImage, inRect: rect, fromRect: image.extent)

图像的范围是实际像素，而 View 的边界是点，并且不会通过 contentScaleFactor 调整以获得像素。您的设备无疑具有 2.0 的 contentScaleFactor ，因此它是每个维度的 1/2。

相反，将矩形设置为:

var rect = CGRect(x: 0, y: 0, width: glView.drawableWidth, 
                             height: glView.drawableHeight)

drawableWidth和 drawableHeight返回以像素为单位的尺寸，考虑 contentScaleFactor。看:
https://developer.apple.com/reference/glkit/glkview/1615591-drawablewidth

另外，glView 的 contentScaleFactor 也不需要设置。