将 UIImage 转换为 CIImage 返回 nil [英] Converting UIImage to CIImage Returns nil

问题描述

我正在尝试将 UIImage 从 imageView 转换为 CIImage 以对其进行过滤.但是，我无法让 CIImage 具有值.

I'm trying to convert the UIImage from an imageView into a CIImage for the purpose of filtering it. However, I cannot get the CIImage to have a value.

以最简单的形式，这就是我正在尝试的:

In the simplest form, here's what I am trying:

let ciInput = CIImage(image: imageView.image!)

但 ciInput 始终为零.我也试过

but the ciInput always is nil. I have also tried

let ciInput = CIImage(cgImage: imageView.image!.cgImage)

但也返回 nil.

(imageView.image 不是 nil，但是 imageView.image!.cgImage 和 imageView.image!.ciImage 都是 nil)

(imageView.image is not nil, but imageView.image!.cgImage and imageView.image!.ciImage are both nil)

我需要将 UIImage 从 imageView 转换为有效的 CIImage.感谢任何帮助，谢谢！

I need to convert the UIImage from the imageView into a valid CIImage. Any help is appreciated, thanks!

这是完整的功能代码

func makeWhiteTransparent(imageView: UIImageView) {

    let invertFilter = CIFilter(name: "CIColorInvert")
    let ciContext = CIContext(options: nil)

    let ciInput = CIImage(image: imageView.image!) //This is nil
    invertFilter?.setValue(ciInput, forKey: "inputImage")

    let ciOutput = invertFilter?.outputImage
    let cgImage = ciContext.createCGImage(ciOutput!, from: (ciOutput?.extent)!)

    imageView.image = UIImage(cgImage: cgImage!)
}

当运行这个函数时，我在最后一行得到一个致命的解包 nil 错误.使用调试器，我发现 ciInput 是 nil，它不应该是.

When running this function, I get a fatal unwrapping nil error on the last line. Using the debugger, I discovered that the ciInput is nil, which it should not be.

编辑 2:调用makeWhiteTransparent之前imageView上的图片就是用这个函数生成的二维码:

EDIT 2: The image on the imageView before calling makeWhiteTransparent is a QR code generated with this function:

func generateQRCode(from string: String) -> UIImage? {
    let data = string.data(using: String.Encoding.ascii)

    if let filter = CIFilter(name: "CIQRCodeGenerator") {
        filter.setValue(data, forKey: "inputMessage")

        let transform = CGAffineTransform(scaleX: 12, y: 12)

        if let output = filter.outputImage?.applying(transform) {
            return UIImage(ciImage: output)
        }
    }

    return nil
}

推荐答案

所以问题出在我的二维码生成上.该代码从 CIImage 返回一个 UIImage，而没有正确利用 CGContext 返回 UIImage.这是解决问题的更正后的二维码功能.

So the problem was in my QR Code generation. The code returned a UIImage from a CIImage without properly utilizing CGContext to return the UIImage. Here is the corrected QR Code function that fixed the issue.

func generateQRCode(from string: String) -> UIImage? {
    let data = string.data(using: String.Encoding.ascii)

    if let filter = CIFilter(name: "CIQRCodeGenerator") {
        filter.setValue(data, forKey: "inputMessage")

        let transform = CGAffineTransform(scaleX: 12, y: 12)

        if let output = filter.outputImage?.applying(transform) {
            let context = CIContext()
            let cgImage = context.createCGImage(output, from: output.extent)
            return UIImage(cgImage: cgImage!)
        }
    }

    return nil
}

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