Edit Parametric Brushes in GIMP Brush Editor

Parametric brushes in GIMP offer dynamic, vector-like shapes that can be customized on the fly without loss of quality. This guide explains how to access GIMP's Brush Editor and adjust three critical parameters: the aspect ratio, rotation angle, and spike count. By tweaking these settings, you can transform standard round tips into custom chisels, calligraphic pens, and multi-pointed polygon stamps for your projects.

Accessing the Brush Editor

  1. Open GIMP and navigate to the Brushes dock (found via Windows > Dockable Dialogs > Brushes).
  2. Select any parametric brush. Parametric brushes are generated shapes, indicated by simple geometric previews (circles, squares, or diamonds), rather than static images.
  3. Open the editor by clicking the Edit Brush icon at the bottom of the Brushes dialog, or simply double-click the selected brush. The Brush Editor window will appear.

Adjusting the Aspect Ratio

The Aspect Ratio setting squashes or stretches the brush tip, changing a symmetrical shape into an elongated or flattened stroke.

  • Locate the Aspect Ratio slider in the Brush Editor.
  • A value of 0.0 maintains the brush's default proportions (a perfect circle or square).
  • Move the slider to the right to increase the value (up to 20.0). As the number increases, the brush flattens, converting a circular tip into an elliptical oval or a flat ribbon, ideal for calligraphy and angled shading.

Adjusting the Angle

The Angle setting controls the orientation of the brush tip, rotating it around its center point.

  • Locate the Angle slider in the Brush Editor.
  • Drag the slider or type a value between 0.0 and 180.0 degrees.
  • Rotating a standard, fully round brush tip will produce no visible change. However, once you adjust the Aspect Ratio or Spike Count, altering the Angle tilts the brush orientation to match your desired stroke direction.

Adjusting the Spike Count

The Spikes setting adds points to the perimeter of the brush tip, transforming basic shapes into polygons or star-like patterns.

  • Locate the Spikes slider in the Brush Editor.
  • A default value of 2 creates an oval or two-pointed shape when stretched.
  • Increase the value to add more vertices. For instance, setting the slider to 3 creates a triangle, 4 creates a diamond or cross, and higher values generate multi-pointed stars or complex polygonal tips.
  • Pair this with the Hardness slider to control whether the spikes have sharp, crisp edges or soft, blended gradients.