Asking the internet for help to make sure I'm not being stupid.

Leaky16BPCTiff.m

/*
This sample shows how CGImageSourceCreateThumbnailAtIndex leaks something akin 
to the memory behind a CGImageRef when asked to create a thumbnail for a 16bpc
TIFF image if one isn't present.

Full sample project here:
http://shapeof.com/archives/2019/media/SixteenBitPerComponentThumbnailLeak.zip
*/


void report_memory(void) {
  struct task_basic_info info;
  mach_msg_type_number_t size = sizeof(info);
  kern_return_t kerr = task_info(mach_task_self(),
                                 TASK_BASIC_INFO,
                                 (task_info_t)&info,
                                 &size);
  if( kerr == KERN_SUCCESS ) {
      NSLog(@"Used memory (in mb): %f", (double)info.resident_size / 1024.0 / 1024.0);
  } else {
    NSLog(@"Error with task_info(): %s", mach_error_string(kerr));
  }
}


- (void)loadThumbnailsForImageWithName:(NSString *)name {
    
    @autoreleasepool {
        
        NSLog(@"Loading image %@", name);
        NSURL *sixteenURL = [[NSBundle mainBundle] URLForImageResource:name];
        assert(sixteenURL);
         
        CGImageSourceRef imageSourceRef = CGImageSourceCreateWithURL((CFURLRef)sixteenURL, nil);
        
        for (int i = 0; i < 500; i++) {
         
            CGImageRef r = CGImageSourceCreateThumbnailAtIndex(imageSourceRef, 0, (CFDictionaryRef)@{(id)kCGImageSourceCreateThumbnailFromImageIfAbsent: @(YES), (id)kCGImageSourceThumbnailMaxPixelSize:@(256), (id)kCGImageSourceCreateThumbnailWithTransform: @(YES)});

            assert(r);
             
            CGImageRelease(r);
        }
         
        CFRelease(imageSourceRef);
        
        NSLog(@"Finished with image %@", name);
    }
}

- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {
    
    report_memory();

    [self loadThumbnailsForImageWithName:@"EightBit"];

    report_memory();

    [self loadThumbnailsForImageWithName:@"SixteenBit"];

    report_memory();
}