UIImageJPEGRepresentation返回nil（在设备上 - 模拟器上的OK）

Question

当我使用generateBarcode（“ABCDEF”）创建条形码UIImage并调用 UIImageJPEGRepresentation 或 UIImagePNGRepresentation

UIImage中显然还有一些问题，因为调试器也无法显示UIImage。图像存在，cgImage属性已设置但UIImageJPEGRepresentation不喜欢它。

我试图按照UIImageJPEGRepresentation returns nil

解决它

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

    if let filter = CIFilter(name: "CICode128BarcodeGenerator") {
        filter.setValue(data, forKey: "inputMessage")
        if let ciImage = filter.outputImage {  
            if let cgImange = convertCIImageToCGImage(inputImage: ciImage) {
                return UIImage(cgImage: cgImange)
            }
        }  
    }  
    return nil  
} 

class func convertCIImageToCGImage(inputImage: CIImage) -> CGImage? {
    let context = CIContext(options: nil)
    if let cgImage = context.createCGImage(inputImage, from: inputImage.extent) {
        return cgImage
    }
    return nil
}