building photoshop-style black-white-conversion

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Hi all!

I'm trying to separate some coloured object from my background. Before starting with OpenCV I'm using a test image in Photoshop to check which color channels or which combination of color channels are the best.

There is a filter "black-and-white" (which is in fact a grayscale converter) which offers 6 trackbars for each shade of the colors:
red, yellow, green, cyan, blue, magenta
reaching from -200 to +300

I then try to find the best combination of this 6 settings to seperate my object as good as possible (for example the background becomes black, the object white).
If I found the perfect combination, how will an algorithm in OpenCV look to rebuild this gray-scale conversion using the values found in Photoshop?

Thanks and regards!