为什么这个 Swift UIImage 函数会溢出我的内存？

Question

我正在使用 Swift 4 为 iPhone 构建一个应用程序。我有一些测试过滤器。两者都可以通过相机的输出正常工作，但是当我从更复杂的图像中创建一组图像时，我的内存溢出到灾难性的比例并使我的应用程序崩溃。

我在下面的循环中调用这个，这会溢出我的记忆：

func rotateHue2(with ciImage: CIImage,
               rotatedByHue deltaHueRadians: CGFloat,
               orientation:UIImageOrientation?,
               screenWidth:CGFloat,
               screenHeight:CGFloat) -> UIImage {


    let sourceCore = ciImage


    let transBG = UIImage(color: .clear, size: CGSize(width: screenWidth, height: screenHeight))

    let transBGCI = CIImage(cgImage: (transBG?.cgImage)!)



    // Part 1

    let gradientPoint0Pos: [CGFloat] = [0, 0]
    let inputPoint0Vector = CIVector(values: gradientPoint0Pos, count: gradientPoint0Pos.count)

    var gradientPoint1Pos: [CGFloat]
    if(orientation == nil){

        gradientPoint1Pos = [0, screenWidth*2]

    }else{

        gradientPoint1Pos = [screenHeight*2, 0]

    }

    let inputPoint1Vector = CIVector(values: gradientPoint1Pos, count: gradientPoint1Pos.count)


    let gradientFilter = CIFilter(name: "CISmoothLinearGradient")
    gradientFilter?.setDefaults()
    gradientFilter?.setValue(inputPoint0Vector, forKey: "inputPoint0")
    gradientFilter?.setValue(inputPoint1Vector, forKey: "inputPoint1")


    gradientFilter?.setValue(CIColor.clear, forKey:"inputColor0")
    gradientFilter?.setValue(CIColor.black, forKey:"inputColor1")


    let gradient = gradientFilter?.outputImage?
        .cropped(to: sourceCore.extent)



    let hue1 = sourceCore
        .applyingFilter("CIHueAdjust", parameters: [kCIInputImageKey: sourceCore,
                                                    kCIInputAngleKey: deltaHueRadians])
        .cropped(to: sourceCore.extent)


    let alphaMaskBlend1 = CIFilter(name: "CIBlendWithAlphaMask",
                                   withInputParameters: [kCIInputImageKey: hue1,
                                                         kCIInputBackgroundImageKey: transBGCI,
                                                         kCIInputMaskImageKey:gradient!])?.outputImage?
        .cropped(to: sourceCore.extent)


    // Part 2


    let hue2 = sourceCore
        .applyingFilter("CIHueAdjust", parameters: [kCIInputImageKey: sourceCore,
                                                    kCIInputAngleKey: deltaHueRadians+1.5707])
        .cropped(to: sourceCore.extent)


    let blendedMasks = hue2
        .applyingFilter(compositeOperationFilters[compositeOperationFiltersIndex], parameters: [kCIInputImageKey: alphaMaskBlend1!,
                                                                                                kCIInputBackgroundImageKey: hue2])
        .cropped(to: sourceCore.extent)




    // Convert the filter output back into a UIImage.
    let context = CIContext(options: nil)
    let resultRef = context.createCGImage(blendedMasks, from: blendedMasks.extent)

    var result:UIImage? = nil

    if(orientation != nil){

        result = UIImage(cgImage: resultRef!, scale: 1.0, orientation: orientation!)

    }else{

        result = UIImage(cgImage: resultRef!)

    }
    return result!
}

根据手机的方向，将每张图片的大小调整为 1280 或 720 宽。当我的其他图像过滤器正常工作时，为什么这会给我一个内存警告？

只是为了好玩，这是另一个不会让它崩溃的：

func rotateHue(with ciImage: CIImage,
                rotatedByHue deltaHueRadians: CGFloat,
                orientation:UIImageOrientation?,
                screenWidth:CGFloat,
                screenHeight:CGFloat) -> UIImage {


    // Create a Core Image version of the image.
    let sourceCore = ciImage
    // Apply a CIHueAdjust filter
    let hueAdjust = CIFilter(name: "CIHueAdjust")
    hueAdjust?.setDefaults()
    hueAdjust?.setValue(sourceCore, forKey: "inputImage")
    hueAdjust?.setValue(deltaHueRadians, forKey: "inputAngle")

    let resultCore = CIFilter(name: "CIHueAdjust",
                              withInputParameters: [kCIInputImageKey: sourceCore,
                                                    kCIInputAngleKey: deltaHueRadians])?.outputImage?
        .cropped(to: sourceCore.extent)


    // Convert the filter output back into a UIImage.
    let context = CIContext(options: nil)
    let resultRef = context.createCGImage(resultCore!, from: (resultCore?.extent)!)

    var result:UIImage? = nil

    if(orientation != nil){

        result = UIImage(cgImage: resultRef!, scale: 1.0, orientation: orientation!)

    }else{

        result = UIImage(cgImage: resultRef!)

    }
    return result!
}

Answer 1

您应该做的第一件事是将您的CIContext 移出函数并使其尽可能全局化。创建它是内存的主要用途。

问题不大，为什么每张图片要裁剪五次？这可能不是问题，但对我来说“感觉”是错误的。 CIImage 不是图像 - 它更接近“配方”。

更紧密地链接事物 - 让下一个过滤器的输入成为前一个过滤器的输出。完成后裁剪。最重要的是，尽可能少地创建CIContexts。