ImageIO:<错误>JPEG 损坏的 JPEG 数据:iphone 数据段过早结束 - 如何捕捉到这个?

ImageIO: lt;ERRORgt; JPEG Corrupt JPEG data: premature end of data segment iphone - how to catch this?(ImageIO:lt;错误gt;JPEG 损坏的 JPEG 数据:iphone 数据段过早结束 - 如何捕捉到这个?)

问题描述

我通过 HTTP 下载图像时收到此错误.我查看了 此处的答案，但即使是有效图像不要从函数返回 YES.

I get this error by downloading an image by HTTP. I have looked at the answer here but even the valid images don't return YES from the function.

还有其他想法吗?

获取图像的代码很简单.这发生在后台线程中.

The code to get the image is simple enough. This happens in a background thread.

NSData *data = [NSData dataWithContentsOfURL:[NSURL URLWithString:urlString]];
UIImage *image = [UIImage imageWithData:data];

这是来自该线程的函数:

This is the function from that thread:

- (BOOL)isJPEGValid:(NSData *)jpeg {
    if ([jpeg length] < 4) return NO;
    const char * bytes = (const char *)[jpeg bytes];
    if (bytes[0] != 0xFF || bytes[1] != 0xD8) return NO;
    if (bytes[[jpeg length] - 2] != 0xFF || 
            bytes[[jpeg length] - 1] != 0xD9) return NO;
    return YES;
}

推荐答案

使用无符号字符.然后比较应该可以工作.

Use an unsigned char. Then comparing should work.

const unsigned char * bytes = (const unsigned char *)[jpeg bytes];

而不是

const char * bytes = (const char *)[jpeg bytes];

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