获取内存泄漏 - NSData 转换

Question

我的 iPhone 4 在以下情况下收到内存压力警告：我需要将图像上传到服务器并使用 Amazon s3。我正在使用以下代码将我选择的图像转换为 NSMutableData：

CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)imageData, NULL);

CFDictionaryRef options = (__bridge CFDictionaryRef)@{(id)kCGImageSourceCreateThumbnailWithTransform: (id)kCFBooleanTrue,
                                                      (id)kCGImageSourceCreateThumbnailFromImageIfAbsent: (id)kCFBooleanTrue,
                                                      (id)kCGImageSourceThumbnailMaxPixelSize: [NSNumber numberWithDouble: maxSize],
                                                      (id)kCGImageDestinationLossyCompressionQuality: [NSNumber numberWithDouble:compressionQuality]};

CGImageRef thumbnail = CGImageSourceCreateThumbnailAtIndex(source, 0, options); // Create scaled image

CFStringRef UTI = kUTTypeJPEG;
NSMutableData *destData = [NSMutableData data];
CGImageDestinationRef destination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)destData, UTI, 1, NULL);
if (!destination) {
    NSLog(@"Failed to create image destination");
}
CGImageDestinationAddImage(destination, thumbnail,( __bridge CFDictionaryRef)metadata); // copy all metadata in source to destination
if (!CGImageDestinationFinalize(destination)) {
    NSLog(@"Failed to create data from image destination");
}

if (!destination) CFRelease(destination);
CFRelease(source);
CFRelease(thumbnail);

return [destData copy];

为什么我在循环执行此操作时在第 24 个图像后收到内存警告？

Answer 1

由于您是将此图像作为一个整体加载到内存中，因此它的获取内存有问题。通常我会将图像保存到文档目录，然后使用图像的路径通过多部分上传图像。那只会将图像加载为多部分，因此内存问题不会成为问题。我不知道这是否适用于您正在做的事情。

请告诉我。

Answer 2

这段代码有漏洞。

具体来说，您有一行内容为：

if (!destination) CFRelease(destination);

只有当它是 NULL 时才会释放它，这与您的意图相反：

if (destination) CFRelease(destination);

顺便说一句，如果你按shift+command+B，Xcode 将对您的代码执行静态分析。它会告诉您这个问题（以及代码中的其他一些问题）。它非常擅长发现这些问题。

我可能会建议如下：

- (NSData * _Nullable)processImageData:(NSData *)imageData maxSize:(double)maxSize compressionQuality:(double)compressionQuality metadata:(NSDictionary *)metadata {
    CGImageSourceRef source = CGImageSourceCreateWithData((__bridge CFDataRef)imageData, NULL);

    CFDictionaryRef options = (__bridge CFDictionaryRef)@{(id)kCGImageSourceCreateThumbnailWithTransform: (id)kCFBooleanTrue,
                                                          (id)kCGImageSourceCreateThumbnailFromImageIfAbsent: (id)kCFBooleanTrue,
                                                          (id)kCGImageSourceThumbnailMaxPixelSize: [NSNumber numberWithDouble: maxSize],
                                                          (id)kCGImageDestinationLossyCompressionQuality: [NSNumber numberWithDouble:compressionQuality]};

    CGImageRef thumbnail = CGImageSourceCreateThumbnailAtIndex(source, 0, options); // Create scaled image

    CFRelease(source);

    CFStringRef UTI = kUTTypeJPEG;
    NSMutableData *destData = [NSMutableData data];
    CGImageDestinationRef destination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)destData, UTI, 1, NULL);
    if (!destination) {
        NSLog(@"Failed to create image destination");
        destData = nil;
    } else {
        CGImageDestinationAddImage(destination, thumbnail,(__bridge CFDictionaryRef)metadata); // copy all metadata in source to destination
        if (!CGImageDestinationFinalize(destination)) {
            NSLog(@"Failed to create data from image destination");
            destData = nil;
        }
        CFRelease(destination);
    }

    CFRelease(thumbnail);

    return [destData copy];
}

获取内存泄漏 - NSData 转换

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