GammaBrush -- correct gamma values of brush (V5.0)
GammaBrush(id, red, green, blue)
This function can be used to gamma correct the color channels of the
specified brush. For each color channel, you have to pass a floating
point value that specifies the desired gamma correction. A value of
1.0 means no change, a value smaller than 1.0 darkens the channel, a
value greater than 1.0 lightens the channel.
brush to gamma correct
gamma correction for red channel
gamma correction for green channel
gamma correction for blue channel
GammaBrush(1, 1.5, 1.0, 0.5)
The code above lightens the red channel and darkens the blue channel,
while leaving the green color channel untouched.