Problem with CGImageDestination and file naming

Question

I am capturing images from the camera, using AVCapture as I have need of speed and the standard kit stuff is way too slow. I have problem whereby the file that is being output (an animated GIF) is having it's file name mangles by the CGImageDestination functions...

When I output the NSURL (cast to a CFURLRef) to the log I get the path/filename I intended:

2011-09-04 20:40:25.914 Mover[3558:707] Path as string:.../Documents/91B2C5E8-F925-47F3-B539-15185F640828-3558-000003327A227485.gif

However, once the file is created and saved it actually lists the filename as this:

2011-09-04 20:40:25.960 Mover[3558:707] file: .91B2C5E8-F925-47F3-B539-15185F640828-3558-000003327A227485.gif-TtNT

See the difference? the period at the start and the 4 character suffix? Whats really wierd is that it doesn't always do it, about 40% of the time it works OK. However it's preventing the code working further down the line where I'm listing them with previews in a table view.

Does anyone know why and how to stop it doing this?

Here's the code:

- (void)exportAnimatedGif{

NSString *guidPath = [[NSProcessInfo processInfo] globallyUniqueString];
NSString *tmpPath = [[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] stringByAppendingPathComponent:guidPath];
NSString *path = [tmpPath stringByAppendingPathExtension:@"gif"];
NSLog(@"Path as string:%@", path);
CGImageDestinationRef destination = CGImageDestinationCreateWithURL((CFURLRef)[NSURL fileURLWithPath:path], kUTTypeGIF, [captureArray count], NULL);

NSDictionary *frameProperties = [NSDictionary dictionaryWithObject:[NSDictionary dictionaryWithObject:[NSNumber numberWithFloat:testDisplay3.displayValue]                                   forKey:(NSString *)kCGImagePropertyGIFDelayTime]
                                                            forKey:(NSString *)kCGImagePropertyGIFDictionary];
NSDictionary *gifProperties = [NSDictionary dictionaryWithObject:
                               [NSDictionary dictionaryWithObjectsAndKeys:
                                [NSNumber numberWithInt:2], (NSString *)kCGImagePropertyGIFLoopCount, 
                                [NSNumber numberWithFloat:testDisplay3.displayValue], (NSString*)kCGImagePropertyGIFDelayTime, 
                                [NSNumber numberWithFloat:testDisplay3.displayValue], (NSString*)kCGImagePropertyGIFUnclampedDelayTime,
                                nil]
                                                          forKey:(NSString *)kCGImagePropertyGIFDictionary];
for (int ii = 0; ii < [captureArray count]; ii++) 
{
    UIImage *tmpImg = [[UIImage alloc] init];
    tmpImg = [captureArray objectAtIndex:ii];
    CGImageDestinationAddImage(destination, tmpImg.CGImage, (CFDictionaryRef)frameProperties);
}
CGImageDestinationSetProperties(destination, (CFDictionaryRef)gifProperties);
CGImageDestinationFinalize(destination);
CFRelease(destination);

//TEST OUTPUT GENERATED FILES
NSArray *contents = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject] error:nil];
for (int xx = 0; xx < [contents count]; xx++) 
{
    NSLog(@"file: %@", [contents objectAtIndex:xx]);
}
//END TEST CODE
[captureArray removeAllObjects];
}

Answer 1

AFAIK this is a temporary file that CGImageDestinationFinalize makes, the reason you see them is that CGImageDestinationFinalize failed. I think that if you check the file sizes you'll see that the ones with mangled names have a file size of 0.

I started check for succes after I got these files :)

bool success =  CGImageDestinationFinalize(destination);
CFRelease(destination);
if (success) {
    NSLog(@"animated GIF file created at %@", path);
} else {
    NSLog(@"failed to create gif at %@", path);
}