Increase brightness on camera output.

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Hello,

I am using baxter to perform pick and place using vision processing. I am using OpenCV for colour and shape recognition. Everything works fine, but system is sensitive for lightning conditions in the room. When it is too dark in the room it won't recognise certain colours. I have been playing with HSV values, but I think better solution would be to use some kind of brightness filter on the camera output. Any ideas how to solve the problem ?