The first is to click and drag the left mouse button in the graph area to trace out a section of the LUT. When the left button is released the modified LUT will be applied to the imagery in the main image window. This technique is called direct tracing. While the mouse is moved through the graph, the current position of the cursor is shown in the title bar for the lookup table.
The second method, piecewise interpolation, is performed by pressing the middle button at one point, and dragging out a straight line to a second point.
The third technique allows the user to drag the entire LUT to the left or the right. This is done by pressing the right mouse button in the graph area, and dragging the whole graph left or right before releasing the mouse button. This can also be accomplished in single step increments using the ``left arrow'' and ``right arrow'' buttons while the editing area has input focus.
On motif systems, the drawing area can usually be given input focus by clicking the mouse in it. Alternately, the tab key can be used to traverse the tab groups until the drawing area is selected. Unfortunately, the drawing area will not be highlighted in any special way when it is selected so the user may have to experiment with the arrow keys until it is clear that the drawing area has input focus.
Currently there is no provision for moving the whole LUT up or down.