UIGraphicsGetImageFromCurrentImageContext() - Memory Leak

Question

I am opening the camera with UIImagePickerControllerSourceTypeCamera and a custom cameraOverlayView so I can take multiple photos without the "Use Photo" step.

This is working great, but there is a memory leak in the save photo function. Through a lot of debugging and research I have narrowed it down to the UIGraphicsGetImageFromCurrentImageContext function.

Here is a snippet of code where it happens:

UIGraphicsBeginImageContextWithOptions(timestampedImage.frame.size, timestampedImage.opaque, [[UIScreen mainScreen] scale]);
[[timestampedImage layer] renderInContext:UIGraphicsGetCurrentContext()];
UIImage *finalTimestampImage = UIGraphicsGetImageFromCurrentImageContext();
UIGraphicsEndImageContext();

I have scoured the internet and it seems that the UIGraphicsGetImageFromCurrentImageContext() function (quoted from this SO question) "returns a new autoreleased UIImage and points the finalTimestampImage ivar to it. The previously allocated UIImage is never actually released, the variable to it is just repointed to somewhere else."

I've tried so many solutions that have apparently worked for others:

• Adding timestampedImage.layer.contents = nil; after UIGraphicsEndImageContext

• Adding CGContextRef context = UIGraphicsGetCurrentContext(); and CGContextRelease(context); after UIGraphicsEndImageContext

• Wrapping the above snippet in an NSAutoreleasePool

• Wrapping the entire saveThisPhoto function in an NSAutoreleasePool

• Creating an NSAutoreleasePool when the camera pops up and calling the [pool release] when didReceiveMemoryWarning is called

• Closing the camera popup when didReceiveMemoryWarning is called, hoping it will clear the pool

• Every possibly combination of the above

Yet everything I try, when I take photos I can see the Memory Utilized rising and not falling when I'm repeatedly taking photos on the device.

Does anyone know how I can release the autorelease object created by UIGraphicsGetImageFromCurrentImageContext?

Alternatively, is there an alternative way to make a UIImage out of an UIImageView?

Edit:

Here are the full functions as requested. There's a lot of extra releasing added in there just to try make sure everything is cleaned up. I have gone through and tested for the memory leak with each code block in saveThisPhoto systematically, and it only occurs when the UIGraphicsGetImageFromCurrentImageContext block (snippet above) is run.

- (void)imagePickerController:(UIImagePickerController *)picker didFinishPickingMediaWithInfo:(NSDictionary *)info {

    NSLog(@"SAVING PHOTO");

    [self saveThisPhoto:info];

    picker = nil;
    [picker release];

    info = nil;
    [info release];

}

- (void)saveThisPhoto:(NSDictionary *)info {

    // Get photo count for filename so we're not overriding photos

    int photoCount = 0;

    if ([[NSUserDefaults standardUserDefaults] objectForKey:@"photocount"]) {
        photoCount= [[[NSUserDefaults standardUserDefaults] objectForKey:@"photocount"] intValue];
        photoCount++;
    }

    [[NSUserDefaults standardUserDefaults] setObject:[NSString stringWithFormat:@"%d", photoCount] forKey:@"photocount"];
    [[NSUserDefaults standardUserDefaults] synchronize];

    // Obtaining saving path

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *fileName = [NSString stringWithFormat:@"ri_%d.jpg", photoCount];
    NSString *fileNameThumb = [NSString stringWithFormat:@"ri_%d_thumb.jpg", photoCount];
    NSString *imagePath = [documentsDirectory stringByAppendingPathComponent:fileName];
    NSString *imagePathThumb = [documentsDirectory stringByAppendingPathComponent:fileNameThumb];

    // Extracting image from the picker and saving it

    NSString *mediaType = [info objectForKey:UIImagePickerControllerMediaType];

    // SAVE TO IPAD AND DB

    if ([mediaType isEqualToString:@"public.image"]){

        // Get Image

        UIImage *editedImage = [info objectForKey:UIImagePickerControllerOriginalImage];

        // Figure out image orientation

        CGSize resizedSize;
        CGSize thumbSize;

        if (editedImage.size.height > editedImage.size.width) {
            resizedSize = CGSizeMake(480, 640);
            thumbSize = CGSizeMake(150, 200);
        } else {
            resizedSize = CGSizeMake(640, 480);
            thumbSize = CGSizeMake(150, 113);
        }

        // MAKE NORMAL SIZE IMAGE

        UIImage *editedImageResized = [editedImage resizedImage:resizedSize interpolationQuality:0.8];

        // clean up the one we won't use any more

        editedImage = nil;
        [editedImage release];

        // ADD TIMESTAMP TO IMAGE

        // make the view

        UIImageView *timestampedImage = [[UIImageView alloc] initWithImage:editedImageResized];
        CGRect thisRect = CGRectMake(editedImageResized.size.width - 510, editedImageResized.size.height - 30, 500, 20);

        // clean up

        editedImageResized = nil;
        [editedImageResized release];

        // make the label

        UILabel *timeLabel = [[UILabel alloc] initWithFrame:thisRect];
        timeLabel.textAlignment =  UITextAlignmentRight;
        timeLabel.textColor = [UIColor yellowColor];
        timeLabel.backgroundColor = [UIColor clearColor];
        timeLabel.font = [UIFont fontWithName:@"Arial Rounded MT Bold" size:(25.0)];
        timeLabel.text = [self getTodaysDateDatabaseFormat];
        [timestampedImage addSubview:timeLabel];

        // clean up what we won't use any more

        timeLabel = nil;
        [timeLabel release];

        // make UIIMage out of the imageview -- MEMORY LEAK LOOKS LIKE IT IS IN THIS BLOCK

        NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];

        UIGraphicsBeginImageContextWithOptions(timestampedImage.frame.size, timestampedImage.opaque, [[UIScreen mainScreen] scale]);
        [[timestampedImage layer] renderInContext:UIGraphicsGetCurrentContext()];
        UIImage *finalTimestampImage = UIGraphicsGetImageFromCurrentImageContext();
        UIGraphicsEndImageContext();
        timestampedImage.layer.contents = nil;
        CGContextRef context = UIGraphicsGetCurrentContext();
        CGContextRelease(context);

        // clean up the one we won't use any more

        timestampedImage = nil;
        [timestampedImage release];

        // SAVE NORMAL SIZE IMAGE TO DOCUMENTS FOLDER

        NSData *webDataResized = UIImageJPEGRepresentation(finalTimestampImage, 1.0); // JPG

        [webDataResized writeToFile:imagePath atomically:YES];

        // clean up the one we won't use any more

        finalTimestampImage = nil;
        [finalTimestampImage release];

        [pool release]; // to get rid of the context image that is stored

        // SAVE TO DATABASE

        [sqlite executeNonQuery:@"INSERT INTO inspection_images (agentid,groupid,inspectionid,areaid,filename,filenamethumb,filepath,orderid,type) VALUES (?, ?, ?, ?, ?, ?, ?, ?,?) ",
         [NSNumber numberWithInt:loggedIn],
         [NSNumber numberWithInt:loggedInGroup],
         myInspectionID,
         [[tableData objectAtIndex:alertDoMe] objectForKey:@"areaid"],
         fileName,
         fileNameThumb,
         documentsDirectory,
         [NSNumber numberWithInt:photoCount],
         [NSNumber numberWithInt:isPCR]
         ];

        // Clean up

        webDataResized = nil;
        [webDataResized release];

    } else {

        NSLog(@">>> IMAGE ***NOT*** SAVED");

    }

    NSLog(@"IMAGE SAVED - COMPLETE");

    info = nil;
    [info release];

}

Answer 1

You're setting your variables to nil before releasing them, and some are already auto released.

Normally when using release you should release and them set to nil.

[var release]
var = nil;

But in some of these you should not be calling release.

The following one is your main culprit.

    // clean up the one we won't use any more

    timestampedImage = nil;
    [timestampedImage release];

    // SAVE NORMAL SIZE IMAGE TO DOCUMENTS FOLDER