I am using Emgu C#.

I acquire images from my cameras.

I know when there is no saturation (ie a grey-tone image) by looking at the average hue channel of the image. If zero then pretty sure picture taken at night time.

I can also detect how bright an image is by checking the average Luminescence channel.

What I would now like to do is a value for the gamma an contrast of an image.

Now, I know it is the interpretation of this hypothetical gamma and contrast that determines its value within the context of how I use it. But what factors can i use to attempt to put a scale on these values?

Should I be looking at a different Color Space?



1 Answer 1


You should take a photograph of an object with known color values, such as Macbeth chart:

enter image description here

By using the lowest row of grayscale colors, you will be able to find out the tone-mapping (sometimes incorrectly called gamma) of your imaging system.

  • $\begingroup$ Hi, interesting but how would I apply that to a live stream? I though that gamma is almost like contrast where it is 'highs' and 'lows' of an image that distinguishes its 'intensity'? Would this not server better as saturation correction. Of course, I may not have a clue what I am talking about $\endgroup$ Jan 31, 2015 at 16:28
  • 2
    $\begingroup$ en.wikipedia.org/wiki/Tone_mapping - this might clear things out $\endgroup$ Jan 31, 2015 at 17:19

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