On 1 Jun 2010, at 02:41, Ken Tozier wrote:
> Hi
>
> I'm trying to write a thumbnailer class that takes a path to a photo and
> creates a thumbnail at a user specified size. The code creates the thumbnails
> OK, but there's this monster memory leak, to the tune of about 100 MB every
> 3-4 seconds, that seems to be related to NSImage.
Have you tried using Instruments? It was built for this sort of thing.
Are you sure that it is a leak and not just the memory usage pattern.
You can trigger a collection with [[NSGarbageCollector defaultCollector]
collectExhaustively];
>
> What's happening is that if I comment out the line that initializes a new
> image, the memory leak disappears.
If don't allocate anything then you won't get ANY memory usage!
> I've tried forcibly releasing the images, tried autoreleasing them, tried
> creating a fixed size buffer into which all the images are read, nothing
> seems to work.
With GC release et al are no-ops so calling them does nothing.
>
> I'm using garbage collection, so that along with the deliberate releasing of
> the images, makes me wonder why the collector isn't getting the hint, that
> it's ok to release the memory for these photos. Could someone point out what
> I'm doing in the following code that prevents the images from getting
> released?
>
> Thanks for any help
>
> - (NSString *) createJPEGThumbnail:(NSString *) inPath
> site:(NSString *) inSite
> {
> NSDictionary *siteRecord,
> *pubRecord;
>
> NSString *sourceName =
> [inPath lastPathComponent],
> *sourceRoot
> = [sourceName stringByDeletingPathExtension],
> *destName
> = [[sourceRoot stringByAddingPercentEscapesUsingEncoding:
> NSUTF8StringEncoding] stringByAppendingPathExtension: @"jpg"],
> *pubCode
> = [self pubCodeFromPath: inPath],
> *thumbPath;
>
> NSFileManager *manager =
> [NSFileManager defaultManager];
>
> siteRecord = [thumbDirectories
> objectForKey: inSite];
> pubRecord = [[siteRecord objectForKey:
> @"publications"] objectForKey: pubCode];
>
> if (pubRecord == nil)
> pubRecord = [[siteRecord objectForKey:
> @"publications"] objectForKey: @"~MISCELLANEOUS"];
>
> thumbPath = [[pubRecord objectForKey:
> @"thumb_path"] stringByAppendingPathComponent: destName];
>
> if (![manager fileExistsAtPath: thumbPath])
> {
> // I've tried both of these, didn't make the slightest
> difference.
> // Both leaked memory at a furious pace
>
> // Option 1:
> NSImage *image
> = [[[NSImage alloc] initWithContentsOfFile: inPath] autorelease];
>
> /* do some stuff */
What happens to image here?
If a reachable reference is created to image then the collector will not
scavenge it.
>
>
> // Option 2
> NSImage *image
> = [[NSImage alloc] initWithContentsOfFile: inPath];
>
> /* do some stuff */
>
> [image release];
> }
>
> // make sure it worked
> if ([manager fileExistsAtPath: thumbPath])
> return thumbPath;
> else
> return nil;
> }
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