为什么我不能在我的Swift iOS应用程序中使用CIFilter将我的图像反转回原始图像 [英] Why can't I invert my image back to original with CIFilter in my Swift iOS app

问题描述

我正在开发一个简单的应用程序。
它有一个带有预加载图像和按钮的图像视图。
按下按钮时，应该反转图像视图中的图像。

I'm working on a simple app. It has an image view with pre-loaded image and a button. When pressed the button should invert the image in the image view.

它第一次运行，但是当我再次按下按钮时，我希望它将图像反转回原始形状。
但是第二次按下按钮就会崩溃。

It works the first time, but I expect it to invert the image back to its original form when I press the button again. However it crashes on this second press of the button.

以下是来自 ViewController.swift的相关代码：

    @IBOutlet weak var imageView: UIImageView!
    @IBOutlet weak var invertButton: UIButton!

    @IBAction func invertButtonPressed(sender: UIButton) {
        let beginImage = CIImage(image: imageView.image!)
        let filter = CIFilter(name: "CIColorInvert")!
        filter.setValue(beginImage, forKey: kCIInputImageKey)
        imageView.image = UIImage(CIImage: (filter.outputImage)!)
    }

基本上， beginImage 变成 nil 第二个时间到了，我不明白为什么。我已经尝试通过将那些密集线分成尽可能多的让赋值进行调试，但是 CIImage 神秘地发生了一些事情。构造函数。有什么想法？

Basically, beginImage becomes nil the second time around and I have no idea why. I have tried debugging by splitting those dense lines into as many let assignments as I can but something mysteriously happens with that CIImage constructor. Any ideas?

推荐答案

问题是这一行：

imageView.image = UIImage(CIImage: (filter.outputImage)!)

<你不能这样做。 CIImage并没有神奇地变成UIImage。图像视图需要基于位图的图像，而不是基于CIImage的图像。您必须渲染 CIImage才能将其转换为UIImage，方法是获取CIContext并告诉它创建CGImage或将CIImage绘制到图形上下文中。

You can't do that. A CIImage does not magically turn into a UIImage. An image view needs a bitmap-based image, not a CIImage-based image. You have to render the CIImage to turn it into a UIImage, either by getting a CIContext and telling it to create CGImage or by drawing the CIImage into a graphics context.

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