绘制CIImage太慢了

Question

我正在创建一个应用程序，需要实时应用过滤器的图像。将UIImage转换为CIImage和应用过滤器都是非常快的操作，但是要将创建的CIImage转换回CGImageRef并显示图像(1/5秒，如果编辑需要实时的话，这实际上是很多事情)。

图像大小约为2500×2500像素，这很可能是问题的一部分。

目前，我正在使用

let image: CIImage //CIImage with applied filters
let eagl = EAGLContext(API: EAGLRenderingAPI.OpenGLES2)
let context = CIContext(EAGLContext: eagl, options: [kCIContextWorkingColorSpace : NSNull()])

//this line takes too long for real-time processing
let cg: CGImage = context.createCGImage(image, fromRect: image.extent)

我已经研究过使用EAGLContext.drawImage()

context.drawImage(image, inRect: destinationRect, fromRect: image.extent)

然而，我找不到任何关于这件事是如何完成的可靠的文档，或者它是否会更快。

是否有更快的方法将CIImage显示到屏幕上(无论是在UIImageView中还是直接在CALayer上)？我想避免降低太多的图像质量，因为这可能是明显的用户。

Answer 1

最后我使用了context.drawImage(image, inRect: destinationRect, fromRect: image.extent)方法。下面是我创建的图像视图类

import Foundation
//GLKit must be linked and imported
import GLKit

class CIImageView: GLKView{
    var image: CIImage?
    var ciContext: CIContext?

    //initialize with the frame, and CIImage to be displayed
    //(or nil, if the image will be set using .setRenderImage)
    init(frame: CGRect, image: CIImage?){
        super.init(frame: frame, context: EAGLContext(API: EAGLRenderingAPI.OpenGLES2))

        self.image = image
        //Set the current context to the EAGLContext created in the super.init call
        EAGLContext.setCurrentContext(self.context)
        //create a CIContext from the EAGLContext
        self.ciContext = CIContext(EAGLContext: self.context)
    }

    //for usage in Storyboards
    required init?(coder aDecoder: NSCoder){
        super.init(coder: aDecoder)

        self.context = EAGLContext(API: EAGLRenderingAPI.OpenGLES2)
        EAGLContext.setCurrentContext(self.context)
        self.ciContext = CIContext(EAGLContext: self.context)
    }

    //set the current image to image
    func setRenderImage(image: CIImage){
        self.image = image

        //tell the processor that the view needs to be redrawn using drawRect()
        self.setNeedsDisplay()
    }

    //called automatically when the view is drawn
    override func drawRect(rect: CGRect){
        //unwrap the current CIImage
        if let image = self.image{
            //multiply the frame by the screen's scale (ratio of points : pixels),
            //because the following .drawImage() call uses pixels, not points
            let scale = UIScreen.mainScreen().scale
            let newFrame = CGRectMake(rect.minX, rect.minY, rect.width * scale, rect.height * scale)

            //draw the image
            self.ciContext?.drawImage(
                image,
                inRect: newFrame,
                fromRect: image.extent
             )
        }
    }   
}

然后，使用它，简单地

let myFrame: CGRect //frame in self.view where the image should be displayed
let myImage: CIImage //CIImage with applied filters

let imageView: CIImageView = CIImageView(frame: myFrame, image: myImage)
self.view.addSubview(imageView)

在将UIImage转换为CIImage之前，将其调整为屏幕大小也有帮助。在高质量图像的情况下，它大大加快了速度。只需确保使用全尺寸的图像时，实际保存它。

就这样！然后，更新视图中的图像。

imageView.setRenderImage(newCIImage)
//note that imageView.image = newCIImage won't work because
//the view won't be redrawn

Answer 2

这可能是值得考虑的金属和显示与一个MTKView。

您将需要一个可以用MTLCreateSystemDefaultDevice()创建的金属设备。用于创建命令队列和核心图像上下文。这两个对象都是持久的，实例化成本也很高，因此理想情况下应该只创建一次：

lazy var commandQueue: MTLCommandQueue =
{
    return self.device!.newCommandQueue()
}()

lazy var ciContext: CIContext =
{
    return CIContext(MTLDevice: self.device!)
}()

您还需要一个颜色空间：

let colorSpace = CGColorSpaceCreateDeviceRGB()!

当涉及到呈现CIImage时，您需要创建一个短暂的命令缓冲区：

let commandBuffer = commandQueue.commandBuffer()

您将希望将您的CIImage (我们称之为image)呈现为MTKView的currentDrawable?.texture。如果这被绑定到targetTexture，则呈现语法是：

    ciContext.render(image,
        toMTLTexture: targetTexture,
        commandBuffer: commandBuffer,
        bounds: image.extent,
        colorSpace: colorSpace)

    commandBuffer.presentDrawable(currentDrawable!)

    commandBuffer.commit()

我有一个工作版本的这里。

希望这能帮上忙！

西蒙

Answer 3

您可以像使用GlkView ()一样使用context.drawImage和呈现：

let glView = GLKView(frame: superview.bounds, context: EAGLContext(API: .OpenGLES2))
let context = CIContext(EAGLContext: glView.context)

处理后呈现图像：

glView.bindDrawable()
context.drawImage(image, inRect: destinationRect, fromRect: image.extent)
glView.display()