If the black (left most) triangle for the input is dragged to the right the middle grey triangle will move proportionately to leave the transform line to remain a single straight segment. The effect is that all pixels at or lower than the new setting for the lower value (originally 0) will be mapped to the lower output value (still 0) resulting in a transform as follows:
Similarly, if the white (right most) triangle for the input is now dragged to the left then all input pixel values at or greater than that setting will be mapped to the maximum output value, with a transform of:
