PixInsight 1.5

The Officially Unofficial Reference Guide

Rev.0.1 – 3/29/2010

Section 13: Morphology


The MorphologicalTransform (MT) process is an advanced implementation of several morphological transforms. It does so by applying a function using a structuring element (a mask).

Morphological Filter

Operator: This is the function that will be used for the transformation. PixInsight offers seven different functions:

Interlacing: Defines an interlacing amount.

Iterations: Here you define the number of times (iterations) you want to execute the defined morphological transformation.

Amount: Strength of the morphological transformation.

Selection: This parameter is only applicable when the Morphological selection operator has been selected. When this parameter is smaller than 0.5, the erosion effect is more noticeable. When it is over 0.5, the dilation effect does. In fact, when Selection is equal to zero, we'd be applying a pure erosion transformation, while when this value is 1, we have a pure dilation transformation. With a value of 0.5 we have the same as a morphological median transformation. Strictly speaking, the selection parameter only works as expected when the structural element has a radial symmetry.

Structuring Element

The structuring element acts as a mask to the morphological transformation. PixInsight's implementation of MT allows you to define the x,y size of the structuring elements, preselect a number of structuring elements, or even define your own.

Size: Size of the structuring element.

Way: You can combine several different structural elements (multi-way morphological transformation). Depending on the active structures, this parameter may allow you to select just one way, or more. Once a way is selected, you can then define the morphological features of the structuring element.

Manage: You can load and save different definitions of structuring elements. The manage option presents you with a dialog box to manage your library of structuring elements.

Paint modes: Below the the structural element editing grid, there are three icons that you can use to define your own structural element. From left to right:


The function of the threshold parameters in the MorphologicalTransformation process is to avoid the transformation performing a higher than desirable modification of the original values. In practical terms it acts as an adaptive mask, as it works by achieving a more gradual effect than if it used hard thresholds.

Low: Set a low threshold for the morphological transformation. By increasing the low threshold, we avoid relatively bright pixels to become too dark.

High: Set a high threshold for the morphological transformation. By increasing the high threshold, we avoid relatively dark pixels to become too bright.

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