Frequency Gradient Filter
This filter’s dialog gives access to three parameters.
The first parameter enables to choose the considered axis. It is controlled using a combo-box.
The second one enables to choose between a linear or a logarithmic scale to map the frequences to the resulting color. It is controlled using a combo-box.
The last parameter enables to graphically define the frequency range for which the gradient will be applied to. The lower and upper bounds handles can be dragged as usual sliders. The bounds can be set more precisely using the two spinboxes. To set the range fastly (but with less precision), the lower bound can be changed by left-clicking in the color-ramp and the upper bound can be changed by right-clicking in the color-ramp.
There are one way to access this filter.
By using the ‘Frequency gradient…’ menu entry: