错误的霍夫曼代码？

Question

我正在我的 iPhone 应用程序中进行一些测试，但出现此错误：

<Error>: Corrupt JPEG data: bad Huffman code

我见过一些奇怪的错误，但这个错误真的很奇怪。我还从中得到了一些我不记得的其他损坏错误。让我发布我的代码来按顺序编写这些文件。

第一步：拍照然后保存

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingImage:(UIImage *)image editingInfo:(NSDictionary *)editingInfo {
[picker.parentViewController dismissModalViewControllerAnimated:NO];

uploadImage = image;
int orient = uploadImage.imageOrientation;
NSString *theOrientation = [NSString stringWithFormat: @"%d", orient];

NSLog(@"Check it: 1");

NSString *latestIDQuery = @"";
NSArray *results = [database executeQuery:@"SELECT * FROM processes ORDER BY id DESC LIMIT 0,1"];   
for (NSDictionary *row in results) {
    latestIDQuery = [row valueForKey:@"id"];
}

int latestID = [latestIDQuery intValue];

int newID = latestID + 1;
NSString *newIDString = [[NSString alloc] initWithFormat:@"%d", newID];
NSString *imageURL = [NSString stringWithFormat:@"Documents/%@_process.jpg",newIDString];

NSLog(@"Saving here... %@", imageURL);

NSString *uploadImagePath = [NSString stringWithFormat:@"%@_process.jpg",newIDString];

NSString  *jpgPath = [NSHomeDirectory() stringByAppendingPathComponent:imageURL];
NSLog(@"Needs to write something like this: %@", jpgPath);
[UIImageJPEGRepresentation(uploadImage, 1.0) writeToFile:jpgPath atomically:YES];

[database executeNonQuery:@"INSERT INTO processes (image, album, status, orient, ready) VALUES (?, ?, ' In Queue', ?, 'no');", uploadImagePath, selectedID, theOrientation];

TableViewAppDelegate *dataCeter = (TableViewAppDelegate *)[[UIApplication sharedApplication] delegate];
dataCeter.dataSix = nil;
NSString *databaseURL = [NSString stringWithFormat:@"%@_process.jpg",newIDString];
dataCeter.dataSix = databaseURL;
[self showCaption];
}

第 2 步：开始上传并可能调整其大小：

        NSString *sqlImageUploadPathOne = @"./../Documents/";
        NSString *sqlImageUploadPathTwo = [rowtwo valueForKey:@"image"];
        NSString *getCaption = [rowtwo valueForKey:@"caption"];
        NSString *getTheID = [rowtwo valueForKey:@"id"];
        NSString *getOrientation = [rowtwo valueForKey:@"orient"];

        NSString *jpgPath = [NSString stringWithFormat:@"Documents/%@",sqlImageUploadPathTwo];
        NSString *jpgPathTwo = [NSString stringWithFormat:@"./../Documents/%@",sqlImageUploadPathTwo];
        NSString *yourPath = [NSHomeDirectory() stringByAppendingPathComponent:jpgPath];

        // Resize and Save
        UIImage *tempImageTwo = [UIImage imageNamed:jpgPathTwo];
        float tooBig = 800.0;
        UIImage *tempImage = [self scaleImage:tempImageTwo:tooBig:tooBig];
        NSData *imageDataTwo = [NSData dataWithData:UIImageJPEGRepresentation(tempImage, 0.1)];
        [imageDataTwo writeToFile:jpgPathTwo atomically:YES];

这是用于缩放图像的函数：

- (UIImage *)scaleImage:(UIImage *) image: (float)maxWidth:(float) maxHeight

{

CGImageRef imgRef = image.CGImage;

CGFloat width = CGImageGetWidth(imgRef);
CGFloat height = CGImageGetHeight(imgRef);

if (width <= maxWidth && height <= maxHeight)
{
    return image;
}

CGAffineTransform transform = CGAffineTransformIdentity;
CGRect bounds = CGRectMake(0, 0, width, height);

if (width > maxWidth || height > maxHeight)
{
    CGFloat ratio = width/height;
    if (ratio > 1)
    {
        bounds.size.width = maxWidth;
        bounds.size.height = bounds.size.width / ratio;
    }
    else
    {
        bounds.size.height = maxHeight;
        bounds.size.width = bounds.size.height * ratio;
    }
}
CGFloat scaleRatio = bounds.size.width / width;
UIGraphicsBeginImageContext(bounds.size);
CGContextRef context = UIGraphicsGetCurrentContext();
CGContextScaleCTM(context, scaleRatio, -scaleRatio);
CGContextTranslateCTM(context, 0, -height);
CGContextConcatCTM(context, transform);
CGContextDrawImage(UIGraphicsGetCurrentContext(), CGRectMake(0, 0, width, height), imgRef);
UIImage *imageCopy = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();
return imageCopy;
}

为什么只有我的一些图像会损坏？我是否需要走一条新路并以不同的方式去做？

谢谢，
库尔顿

Answer 1

我觉得这个问题的标题很有趣，我做了一些搜索。维基百科解释说，霍夫曼编码是：

一种用于无损数据压缩的熵编码算法

您的 JPG 数据在某处损坏，iOS SDK 正在报告它。至于如何以及为什么，谷歌有很多结果。

根据这篇文章，似乎 MySQL 可能会损坏您的图像。当然，您的图像可能会在一些地方损坏，因为您正在处理它们。需要更多信息来诊断确切的问题。

编辑：

似乎您的调整大小功能导致了问题。尝试将您的代码与本线程中提到的方法进行比较，看看它们是否会对您有所帮助。正如Matthew Frederick所提到的，Matt Gemmell 的 MGImageUtilities可能正是您所需要的。（虽然我从来没有使用过，甚至从未见过它们。）Matt Gemmell 在 Mac/Objective-C 世界中广为人知。