How to change bgr values?

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I am hoping to change the light intensities of each pixel over an image.

The alternation doesn't follow any particular patterns and formula.

for example x 2 , x (3/2)

There are some target values which are already set or decided on.

For blues ;

0 -> 0 1 -> 2 2 -> 3 3 -> 5 ... ... ...

255 -> 510

How am I supposed to do this?

Please help!