The Gradient effect has the following controls:
Brightness scales the brightness of the computed gradient data.
Input selects the data channel, from which the gradient is computed.
Output defines the channel, to which the gradient data is written.
Monochrome option outputs gradient data as a grayscale image representing the length of gradient values: sqrt(dx*dx + dy*dy). If the option is cleared, dx is written to R component and dy is written to G component. Note that the value range of dx and dy usually includes negative values.