Ios UIImagePNGRepresentation是否返回零数据？

我正在尝试制作缩略图并保存到文档目录。 但问题是，当我试图将缩略图转换为NSData时。它返回零

这是我的密码

  UIImage *thumbNailimage=[image thumbnailImage:40 transparentBorder:0.2 cornerRadius:0.2 interpolationQuality:1.0];
NSData *thumbNailimageData = UIImagePNGRepresentation(thumbNailimage);// Returns nil
[thumbNailimageData writeToFile:[DOCUMENTPATH stringByAppendingPathComponent:@"1.png"] atomically:NO];

那么，我也尝试过UIImageJPEG表示，但它不适合我，这是什么问题呢

谢谢。

试试这段代码

-(void) createThumbnail
{
   UIImage *originalImage = imgView2.image; // Give your original Image
   CGSize destinationSize = CGSizeMake(25, 25); // Give your Desired thumbnail Size
   UIGraphicsBeginImageContext(destinationSize);
   [originalImage drawInRect:CGRectMake(0,0,destinationSize.width,destinationSize.height)];
   UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
   NSData *thumbNailimageData = UIImagePNGRepresentation(newImage);
   UIGraphicsEndImageContext();
   [thumbNailimageData writeToFile:[NSHomeDirectory() stringByAppendingPathComponent:@"1.png"] atomically:NO];
}

希望这对你有帮助， 快乐编码

试试这个：

UIGraphicsBeginImageContext(originalImage.size);
[originalImage drawInRect:CGRectMake(0, 0, originalImage.size.width, originalImage.size.height)];
UIImage *newImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

---

这将创建原始UIImage的副本。然后您可以调用

UIImagePNGRepresentation

，它将正常工作。

对于Swift程序员，Rickster的回答对我帮助很大UIImageJPEGRepresentation在选择特定图像时使我的应用程序崩溃。我正在分享我对UIImage（或Objective-C术语中的类别）的扩展

---

你是否跟踪了thumbNailimage中的图像…？

thumbNailimage

可能也是

nil

尝试使用一个显示thumbNailimage对象的图像视图，并确认该图像是否正确。否，我得到的thumbNailimage对象不是nil。。

import UIKit

extension UIImage {

    /**
     Creates the UIImageJPEGRepresentation out of an UIImage
     @return Data
     */

    func generateJPEGRepresentation() -> Data {

        let newImage = self.copyOriginalImage()
        let newData = UIImageJPEGRepresentation(newImage, 0.75)

        return newData!
    }

    /**
     Copies Original Image which fixes the crash for extracting Data from UIImage
     @return UIImage
     */

    private func copyOriginalImage() -> UIImage {
        UIGraphicsBeginImageContext(self.size);
        self.draw(in: CGRect(x: 0, y: 0, width: self.size.width, height: self.size.height))
        let newImage = UIGraphicsGetImageFromCurrentImageContext()
        UIGraphicsEndImageContext();

        return newImage!
    }
}