Question

My question is very simple, I would like to know if the method “CGImageSourceCreateWithData” creates a new object copying the data I provide so that that I have to release it when I don’t need it anymore, or if it just creates a reference to the data I already have so that if I release it I will lose this data (and possibly have bad access errors).

The issue is related to using (__bridge CFDataRef) as the source data. Which let’s me use Core Foundation objects as toll-free in ARC mode.

Consider the following function (or method, not sure how it’s called):

- (void)saveImageWithData:(NSData*)jpeg andDictionary:(NSDictionary*)dicRef andName:(NSString*)name
{
    [self setCapturedImageName:name];

    CGImageSourceRef  source ;

    // Notice here how I use __bridge
    source = CGImageSourceCreateWithData((__bridge CFDataRef)jpeg, NULL);

    CFStringRef UTI = CGImageSourceGetType(source); 

    NSMutableData *dest_data = [NSMutableData data];

    // And here I use it again
    CGImageDestinationRef destination = CGImageDestinationCreateWithData((__bridge CFMutableDataRef)dest_data,UTI,1,NULL);

    CGImageDestinationAddImageFromSource(destination,source,0, (__bridge CFDictionaryRef) dicRef);

    BOOL success = NO;
    success = CGImageDestinationFinalize(destination);

    if(!success) {
        NSLog(@"***Could not create data from image destination ***");
    }

    // This only saves to the disk
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *documentsDirectory = [paths objectAtIndex:0]; // Get documents folder
    NSString *dataPath = [documentsDirectory stringByAppendingPathComponent:@"ARPictures"];

    NSError *error;
    if (![[NSFileManager defaultManager] fileExistsAtPath:dataPath])
        [[NSFileManager defaultManager] createDirectoryAtPath:dataPath withIntermediateDirectories:NO attributes:nil error:&error]; //Create folder

    NSString *fullPath = [dataPath stringByAppendingPathComponent:[NSString stringWithFormat:@"%@.jpg", name]]; //add our image to the path

    [dest_data writeToFile:fullPath atomically:YES];


    self.img = [[UIImage alloc] initWithData:dest_data]; 
    self.capturedImageData = [[NSData alloc] initWithData:dest_data];

    //This is what im not sure if i should use
    CFRelease(destination);
    CFRelease(source);

}

My concern is about memory leaks or dealocating things I should not.

Thanks

Answer 1

You are doing it correctly. It does not actually matter whether these routines make copies or not. What matters is that you CFRelease what you “Create” (or “Copy”). Everything here looks correct. __bridge is appropriate when passing parameters because you’re not actually transferring the object from CF to Cocoa or vice versa. You’re just temporarily “bridging” (casting) it.