ios7 - 无法在 iOS 上将 CIImage 保存到文件而不发生内存泄漏

Question

以下代码片段保存 CIImage使用 UIImage 到磁盘.

- (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];
}

但是，它泄露了 CGImageRef即使通过调用 CGImageRelease 来释放它

如果该行带有 #if 1更改为#if 0 ，UIImage直接从 CIImage 创建并且没有内存泄漏，但是 UIImage未保存到磁盘

Answer 1

将保存包装在自动释放池中:

- (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目录的方式以适用于 iOS 8 ( more info )。