核心图像GPU性能太慢 [英] Core Image GPU performance too slow

问题描述

我在玩Core Image Filters，遇到了一个奇怪的基准。
具有以下两个功能；顾名思义，一个在cpu上处理大量数学运算，另一个在gpu上处理数学运算，cpu性能比gpu性能快大约一百倍。我尝试使用 CILineOverlay和 CIPhotoEffectProcess滤镜，并使用 DispatchTime.now（）方法测量了转换时间。
我做错什么了吗？

I was playing with Core Image Filters and encountered a strange benchmark. With the following 2 functions; one processing heavy math on cpu and other on gpu as the name suggests, cpu performance is about a hundred times faster than the gpu performance. I tried "CILineOverlay" and "CIPhotoEffectProcess" filters and measured the transforming time with DispatchTime.now() method. Am I doing something wrong? Or is it related to deprecated opengl support?

private func apply_cpu(to image:UIImage?, appleFilterName:String) -> UIImage?    {

    guard let image = image, let cgimg = image.cgImage else {
        return nil
    }

    let coreImage = CIImage(cgImage: cgimg)

    let filter = CIFilter(name: "CISepiaTone")
    filter?.setValue(coreImage, forKey: kCIInputImageKey)
    filter?.setValue(0.5, forKey: kCIInputIntensityKey)

    if let output = filter?.value(forKey: kCIOutputImageKey) as? CIImage {
        return UIImage(ciImage: output)
    }

    else {
        return nil
    }
}


private func apply_gpu(to image:UIImage?, appleFilterName:String)-> UIImage?  {

    guard let image = image, let cgimg = image.cgImage else {

        return nil
    }


    let coreImage = CIImage(cgImage: cgimg)


    let start = DispatchTime.now()

    let openGLContext = EAGLContext(api: .openGLES3)
    let context = CIContext(eaglContext: openGLContext!) 


    guard let filter = CIFilter(name: appleFilterName)   else {
        return nil
    }

    if  filter.inputKeys.contains(kCIInputImageKey) {
        filter.setValue(coreImage, forKey: kCIInputImageKey)
    }

    if  filter.inputKeys.contains(kCIInputIntensityKey) {


    }


    if let output = filter.value(forKey: kCIOutputImageKey) as? CIImage {
        let cgimgresult = context.createCGImage(output, from: output.extent)
        return UIImage(cgImage: cgimgresult!)

    }

        return nil

}

}

推荐答案

在评论中，问题在于进行性能时间测试的位置。在测试 CoreImage 过滤器时，我对此压力不足：

From the comments, the issue was where the performance time tests were being done. I can't stress this enough when testing CoreImage filters:

使用 real 设备，而不是模拟器。

Use a real device, not the simulator.

我的经验是，在任何iPhone 5或更高版本的模拟器中，它可能需要几秒钟到几分钟使用iOS 9+的设备（两种方式都可能更早）将接近实时到毫秒。如果您没有在真实设备上看到此内容？代码中有 错误。

My experience is that it can take "seconds to minutes" in the simulator where in any iPhone 5 or later device using iOS 9+ (maybe earlier too, both ways) will be "near real-time to milliseconds". If you aren't seeing this on a real device? There is something wrong in the code.

我还没有找到任何强调这一点的教程，书籍或任何东西。我最好的资源-Simon Gladman撰写了出色的 Swift核心映像（请注意，它是Swift 2）-解释了我相信正在发生的很多事情，但从未真正强调过为什么会这样

I've not found any tutorials, any books, anything at all that stresses this single point. My best resource - Simon Gladman who wrote the excellent Core Image for Swift (be careful, it's Swift 2) - explains a lot of what I believe is going on, but never really stressed why it is the case.

iOS设备使用GPU。模拟器没有。

An iOS device uses the GPU. A simulator does not.

我相信它比这更复杂，并且涉及优化。事情是这样的-虽然您可以在 macOS 中使用CoreImage，但如果使用的是模拟器，则目标是 iOS 。因此，在使用CoreImage的macOS项目可能表现良好的情况下，如果是iOS项目，则需要使用真实的设备来获得真实的性能感觉。

I'm sure it's more complex than that and involves optimization. But the thing is this - while you can use CoreImage in macOS, if you are using the simulator you are targeting iOS. So where a macOS project using CoreImage may perform well, if it's an iOS project you need to use a real device to get a real feel for performance.

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