The interactive spectrum graph (See Figure 1) displays the radially averaged power spectrum of the input grid as a function of wavenumbers. This spectrum is plotted in black. Once you define a filter, if it has a radial representation, the filter graph will be displayed in blue. The icon flags filters that do not have a radial representation. The filtered spectrum is displayed in red. If a combination of filters is applied, their filter and output spectra acquire other distinct colours. A legend along the bottom of the graph identifies them.

The range of the abscissa spans from 0 to ½ cell size. For convenience and because you provide the parameters in wavelengths rather than wavenumbers, you can toggle between wave numbers and wavelength (1/wavenumber). However, this does not affect the graph.

To allow for a finer control in the longer wavelengths (or lower wavenumbers), the minimum wavelength can be adjusted up to a factor of 10. You can change the range by editing the value at the right end of the abscissa.

The ordinate is annotated with the logarithm of the power spectrum on the left and the range of the filter coefficients on the right. You can change the range of the power spectrum by editing the end values of the ordinate.

When you change the graph range, the reset button (), located at the bottom left of the graph, becomes active and allows you to return to the initial data range.

The Spectrum pane is resizable in both directions. To resize the pane, grab the horizontal or vertical grip by holding the left mouse button down on the grip (Figure 2).

Filter Definition

This is where you define the filter(s) and their parameters. You can choose from a set of 29 filters. MAGMAP will accept up to four concurrent filters. Add filters by clicking on the Add Filter () button located at the bottom right of the pane. Each filter has its own specific parameters. The button located beside each filter provides the detailed description of that filter.

After specifying a filter and clicking <Enter>, all the other panes are updated to reflect the outcome of the new filter combination. As a further convenience, low/high/bandpass filters offer live sliders that allow you to interactively see the effect of their settings.

Select a filter. Up to four filters can be selected from the drop-down list.

The following filters are available:

You will be prompted for additional parameters according to each filter’s requirements. Parameters for each filter can be adjusted either by moving the slider controls where available (), or by entering the values directly in the parameter fields (). After entering a parameter, press the <Enter> key, and the spectra and preview images will automatically update.

Preview Pane

The preview pane offers an interactive view of both the original grid and the filtered grid(s). The images in the two preview windows are linked and the cursor location is tracked. The most recent colour table assigned to the input grid is used to display the images in the preview pane.

The pane is resizable; grab the grip at the bottom right of the pane to resize the pane.

This is an image view of your original grid.

If you selected multiple input grids, the Original grid label is replaced by a drop-down list that contains all the available grids to use for preview. The first in the list is the one initially selected. From the list of input grids, select the grid that you would like to preview:

This is an interactive image view of your filtered grid.

At the onset, this pane is empty. As soon as you define filters, the outcome is reflected in this pane. If you defined multiple filters, the Preview filter result list becomes active and you could view their effect individually or combined.

To zoom into a location on both grids, click the Select and zoom to an area of interest ( ) button.  Note that your cursor changes to a select mode when it crosses either the Original grid or the Filtered grid windows.

Using your cursor, draw a box around the desired area, then click inside the boxed area to zoom to the selected location. 

Click the Show entire data extent () button to return your zoomed images to the original full size.