加快 UIImage 处理速度 Swift

Question

我正在尝试应用下一个代码来为从图库中截取的图像着色：

func zoeFilter() -> UIImage? {
        let brownColor = UIColor (red: 128/255, green: 0, blue: 0, alpha: 1)
        let colorRect = CGRect (origin: .zero, size: self.size)

        let renderer = UIGraphicsImageRenderer (bounds: colorRect)

        let brownColoredImage = renderer.image { ctx in
            ctx.cgContext.setFillColor(greyColor.cgColor)
            ctx.fill(colorRect)
        }

        let outBrown0Image = renderer.image { ctx in
            ctx.cgContext.setFillColor(UIColor.white.cgColor)
            ctx.fill(colorRect)
            self.draw(in: colorRect, blendMode: .normal, alpha: 1)
            brownColoredImage.draw(in: colorRect, blendMode: .colorDodge, alpha: 1)
        }

        let outBrownImage = renderer.image { ctx in
            self.draw(in: colorRect, blendMode: .normal, alpha: 1)
            outBrown0Image.draw(in: colorRect, blendMode: .multiply, alpha: 1)
        }

        return outBrownImage
    }

但是处理图像需要大约 14 秒，这对用户体验来说不是很好...

你知道我怎样才能得到相同的结果但加速图像处理吗？

你有什么建议吗？

提前致谢！

最终解决方案

func zoeFilter() -> UIImage? {
        let inImage = CIImage (image: self)

        let SRGBImage = inImage?.applyingFilter("CILinearToSRGBToneCurve")

        let brownColor = CIColor (red: 128/255, green: 0, blue: 0, alpha: 1)
        let colorRect = CGRect (origin: .zero, size: self.size)

        dynamic let colorFilter = CIFilter(name: "CIConstantColorGenerator")
        dynamic let colorizeFilter = CIFilter (name: "CIColorDodgeBlendMode")
        dynamic let multiplyFilter = CIFilter (name: "CIMultiplyBlendMode")

        colorFilter?.setValue(brownColor, forKey: kCIInputColorKey)
        let brownSolidImage = colorFilter?.outputImage?.cropped(to: colorRect)

        colorizeFilter?.setValue(SRGBImage, forKey: kCIInputBackgroundImageKey)
        colorizeFilter?.setValue(brownSolidImage, forKey: kCIInputImageKey)
        let outBrown0Image = colorizeFilter?.outputImage

        multiplyFilter?.setValue(SRGBImage, forKey: kCIInputBackgroundImageKey)
        multiplyFilter?.setValue(outBrown0Image, forKey: kCIInputImageKey)
        let outBrownImage = multiplyFilter?.outputImage

        let linearImage = outBrownImage?.applyingFilter("CISRGBToneCurveToLinear")

        let cgImage = CIContext().createCGImage(linearImage!, from: linearImage!.extent)
        return UIImage (cgImage: cgImage!)
    }

Answer 1

最简单的尝试是将这 3 个 renderer.image { ... } 调用合并为一个调用。您应该能够将第二个调用的内容移动到第一个调用中。这应该会产生巨大的性能差异。

除此之外，您真的需要对相机胶卷中的全尺寸图像执行此操作吗？如果不是，请在执行所有不需要的渲染之前调整您在渲染器上设置的大小。

通常，当您尝试以高性能方式进行此类过滤时，您会使用 CoreImage。有了它，您可以以非常高的速度处理图像。像 60 fps 过滤实时视频。

我将从查看 Apple 的内置过滤器列表开始： https://developer.apple.com/library/archive/documentation/GraphicsImaging/Reference/CoreImageFilterReference/index.html

这是一个很好的过滤器使用示例： https://www.hackingwithswift.com/articles/204/how-to-use-core-image-filters-the-type-safe-way

如果您发现无法组合内置过滤器来获得效果，您始终可以自己编写非常简单的 Metal backed 过滤器： https://flexmonkey.blogspot.com/2016/01/metal-kernel-functions-as-core-image.html

加快 UIImage 处理速度 Swift

Accelerate UIImage processing speed in Swift

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