An example of concurrent image brightness normalization in C#.

ConcurrentImageBrightnessNormalizer.cs

//determine the brightness range of this thread's image strip
Tuple brightnessRange = GetImagePartBrightnessRange(image, startX, startY, finishX, finishY);

//update the global brightness range of the entire image
lock (_lock)
{
    minBrightness = Math.Min(minBrightness, brightnessRange.Item1);
    maxBrightness = Math.Max(maxBrightness, brightnessRange.Item2);
}

//wait at the barrier until all image strips have been assessed
barrier.Wait();

//now that the brightness range of the entire image is known, normalize the brightness of the image strip
NormalizeImagePart(image, startX, startY, finishX, finishY, minBrightness, maxBrightness);

//raise event so that event listeners are notified that the image strip has been normalized
ImagePartNormalized(this, new ImagePartModifiedEventArgs(startX, startY, finishX, finishY));

bool isLastThread = barrier.Wait();

//if this thread is the last one past the barrier, then we
//can safely assume all image strips have been normalized
if (isLastThread)
{
    //raise event so that event listeners are notified that the normalization is complete
    ImageNormalizationCompleted(this, EventArgs.Empty);
}