无法在没有内存泄漏的情况下将CIImage保存到iOS上的文件 [英] Can't save CIImage to file on iOS without memory leaks

问题描述

以下代码片段使用 UIImage 将 CIImage 保存到磁盘。

The following snippet of code save a CIImage to disk using an UIImage.

- (void)applicationWillResignActive:(UIApplication *)application
{
    NSString* filename = @"Test.png";

    UIImage *image = [UIImage imageNamed:filename];

    // make some image processing then store the output
    CIImage *processedImage = [CIImage imageWithCGImage:image.CGImage];

#if 1// save using context

    CIContext *context = [CIContext contextWithOptions:nil];
    CGImageRef cgiimage = [context createCGImage:processedImage fromRect:processedImage.extent];
    image = [UIImage imageWithCGImage:cgiimage];

    CGImageRelease(cgiimage);

#else

    image = [UIImage imageWithCIImage:processedImage];

#endif

    // save the image

    NSString *filePath = [[[NSBundle mainBundle] bundlePath] stringByAppendingPathComponent:[@"../Documents/" stringByAppendingString:filename]];

    [UIImagePNGRepresentation(image) writeToFile:filePath atomically:YES];
}

然而，它泄漏了 CGImageRef 即使通过调用 CGImageRelease

However, it leaks the CGImageRef even when it is released by calling CGImageRelease

如果 #if 1 更改为 #if 0 ， UIImage 直接从创建CIImage 且没有内存泄漏，但 UIImage 未保存到磁盘

If the line with #if 1 is changed to #if 0, the UIImage is created directly from the CIImage and there are no memory leaks, but then the UIImage is not saved to disk

推荐答案

将保存包装在自动释放池中：

Wrap the saving inside an autorelease pool:

- (void)applicationWillResignActive:(UIApplication *)application
{
    NSString* filename = @"Test.png";

    UIImage *image = [UIImage imageNamed:filename];

    // make some image processing then store the output
    CIImage *processedImage = [CIImage imageWithCGImage:image.CGImage];

    @autoreleasepool {
        CIContext *context = [CIContext contextWithOptions:nil];
        CGImageRef cgiimage = [context createCGImage:processedImage fromRect:processedImage.extent];
        image = [UIImage imageWithCGImage:cgiimage];

        CGImageRelease(cgiimage);

        // save the image
        NSURL *documentsDir = [[[NSFileManager defaultManager] URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask] firstObject];
        NSURL *fileURL = [documentsDir URLByAppendingPathComponent:filename];

        [UIImagePNGRepresentation(image) writeToURL:fileURL atomically:YES];
    }
}

另请注意，我更新了您检索文档的方式适用于iOS 8的目录（更多信息）。

Also note that I updated how you were retrieving the Documents directory to work for iOS 8 (more info).

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