Question

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

这是我的代码，

  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];

那么我用UIImageJPEGRepresentation尝试过的问题是什么，但它对我不起作用。

感谢。

Answer 1

试试这个：

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

这会创建原始UIImage的副本。然后，您可以致电UIImagePNGRepresentation，它将正常运作。

Answer 2

对于Swift程序员来说，Rickster的答案对我帮助很大！ UIImageJPEGRepresentation 在选择某个图片时崩溃了我的应用。我正在分享我的UIImage扩展（或Objective-C术语中的类别）。

Heap(){
        root  = NULL;
        cout << "Do you want\n1.Max Heap\n2.Min Heap";
        cin >> choice;

        if(choice == 1){
        function_variable = max_insert();       
        }else{
            function_variable = min_insert();
        }
            cout << "1.INSERT\2.SEARCH\n3.TRAVERSAL";
            cin >> choice;
            switch(choice){
                case1: function_variable ;break;
                case2: search();break;
                case3:traversal();break;
            }

    }

Answer 3

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];
}

希望这有助于你，快乐编码

UIImagePNGRepresentation返回零数据？

3 个答案: