1-D Warping

1. Select a series of control points to define the distortion to be corrected. For example, if you have an SDS gel in which the bands are U-shaped, trace out a U-shaped curve somewhere on the image that follows the U shape.
2. Press any key. This fixes the curve in place (it becomes invisible).
3. (Vertical warping only) With the mouse, select a y-value somewhere below the lowest point in the curve which you traced out.
4. Click the left mouse button at the desired y-value.
5. Each vertical line on the screen will be shifted up or down so that each point on the curve you traced out is lined up with the selected y-value.

Horizontal warping is similar, except that the pixels are shifted left and right to create a ripple distortion effect similar to a reflection in water. The height of the curve you trace with the mouse determines the distance by which the pixels at the corresponding x coordinate are shifted. (Upleft, down=right).