114     CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceGray();

   114     CGColorSpaceRef colorspace = CGColorSpaceCreateDeviceGray();

   115     CGContextRef bitmapImage = CGBitmapContextCreate(mapExp, 256, 128, 8, 256, colorspace, kCGImageAlphaNone);

   115     CGContextRef bitmapImage = CGBitmapContextCreate(mapExp, 256, 128, 8, 256, colorspace, kCGImageAlphaNone);

   116     CGColorSpaceRelease(colorspace);

   116     CGColorSpaceRelease(colorspace);

   117     

   117     

   118     CGImageRef previewCGImage = CGBitmapContextCreateImage(bitmapImage);

   118     CGImageRef previewCGImage = CGBitmapContextCreateImage(bitmapImage);

   119     UIImage *previewImage = [[UIImage alloc] initWithCGImage:previewCGImage];

   120     UIImage *previewImage = [[UIImage alloc] initWithCGImage:previewCGImage];

   120     CGImageRelease(previewCGImage);

   121     CGImageRelease(previewCGImage);

   121     previewCGImage = nil;

   122     previewCGImage = nil;

   122 

   123 

   123     // set the preview image (autoreleased) in the button and the maxhog label on the main thread to prevent a leak

   124     // set the preview image (autoreleased) in the button and the maxhog label on the main thread to prevent a leak