GtkCurve::set_gamma
Use this function to precisely control a curve using its gamma value. The gamma value of a curves, directly correlates with its radius of curvature. Hence, a gamma value of 1 will result in a straight line. Values greater than 1 will result in bent curves above the straight line, while values lesser than 1 give curves bent under the straight line.
The curve type is automatically changed to Free when this function is
called.