UIImageJPEGRepresentation返回nil

  • Z时代
  • 2024-01-10
  • 分类：问答

我正在使用CIFilters将图像转换为灰度并应用一些图像处理效果。在UIImageView中显示输出有效；图像将显示，并且已按预期进行了修改。

但是，每次调用UIImageJPEGRepresentation似乎都不返回任何数据。它永远都行不通。使用原始彩色图像调用UIImageJPEGRepresentation效果很好。

这里发生了什么？为什么在显示图像时jpeg转换会失败？不会引发任何异常（设置异常断点，不会命中），并且控制台中不会显示任何消息。

let _cicontext = CIContext(options:nil)
// Set up grayscale and blur filters:
let grayIze = CIFilter(name: "CIColorControls")
let blur = CIFilter(name: "CIGaussianBlur")
grayIze.setValue(0, forKey:kCIInputSaturationKey)
grayIze.setValue(0.5, forKey: kCIInputBrightnessKey)
blur.setValue(4, forKey: kCIInputRadiusKey)
// Go!
let originalImage = CIImage(image: colorImageThatDefinitelyExists)
grayIze.setValue(originalImage, forKey: kCIInputImageKey)
blur.setValue(grayIze.outputImage, forKey: kCIInputImageKey)
let output = UIImage(CIImage: blur.outputImage)
let imageData: NSData? = UIImageJPEGRepresentation(output, 1.0) // Returns nil!?

// Define an image context at the class level, which will only be initialized once:
static let imageContext = CIContext(options:nil)
// And here's the updated code in a function:
class func convertToGrayscale(image: UIImage)->UIImage?
{
    // Set up grayscale and blur filters:
    let filter1_grayIze = CIFilter(name: "CIColorControls")
    let filter2_blur = CIFilter(name: "CIGaussianBlur")
    filter1_grayIze.setValue(0, forKey:kCIInputSaturationKey)
    filter1_grayIze.setValue(0.5, forKey: kCIInputBrightnessKey)
    filter2_blur.setValue(4, forKey: kCIInputRadiusKey)
    // Go!
    let originalImage = CIImage(image: image)
    filter1_grayIze.setValue(originalImage, forKey: kCIInputImageKey)
    filter2_blur.setValue(filter1_grayIze.outputImage, forKey: kCIInputImageKey)
    let outputCIImage = filter2_blur.outputImage
    let temp:CGImageRef = imageContext.createCGImage(outputCIImage, fromRect: outputCIImage.extent())
    let ret = UIImage(CGImage: temp)
    return ret
}
// And finally, the function call:
    if let grayImage = ProfileImage.convertToGrayscale(colorImage)
    {
        let imageData: NSData? = UIImageJPEGRepresentation(grayImage, 1.0)
    }

回答：

我之前遇到过CIImage问题，要解决此问题，我先用CIImage制作了CGImage，然后再用CGImage制作了UIImage。

以上是 UIImageJPEGRepresentation返回nil 的全部内容， 来源链接： utcz.com/qa/407485.html

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