How to Stroke a Path with Airbrush Gradient in GIMP

Stroking an open vector path with an airbrush gradient in GIMP allows you to apply smooth, soft-edged, color-shifting strokes along any custom vector line. This process utilizes GIMP's Path tool, the Airbrush tool, and Paint Dynamics to map an active gradient across the length or application of the stroke, offering precise control over opacity, softness, and color transitions.

1. Select and Configure the Gradient

  1. Open the Gradients Dialog (Windows > Dockable Dialogs > Gradients).
  2. Click on the gradient you want to apply to the stroke to make it the active gradient.

2. Configure the Airbrush and Brush Settings

  1. Select the Airbrush Tool (A) from the Toolbox.
  2. In the Tool Options panel:
    • Choose a soft-edged brush (such as 2. Hardness 050 or a soft round brush).
    • Set your desired base Size, Rate, and Flow to determine the density and speed of the airbrush output.

3. Enable Gradient Dynamics

To make the Airbrush apply the selected gradient rather than a flat foreground color, you must link it to Paint Dynamics:

  1. In the Airbrush Tool Options, locate the Dynamics section.
  2. Click the dynamics icon and select Color From Gradient.
  3. Expand Dynamics Options (if available) to set the Fade Length to roughly match the length of your vector path if you want the full gradient to stretch from start to end.

4. Create or Select the Open Vector Path

  1. Select the Paths Tool (B).
  2. Click on your canvas to create the starting point, then click and drag to define subsequent nodes for your open path. Leave the path unclosed (do not click the starting node).
  3. If using an existing path, open the Paths Dialog (Windows > Dockable Dialogs > Paths) and click the path to make it active.

5. Stroke the Path

  1. Ensure the target layer where you want the stroke to appear is selected in the Layers Dialog.
  2. Go to the top menu and select Edit > Stroke Path... (or right-click the path in the Paths dialog and select Stroke Path...).
  3. In the Stroke Path dialog:
    • Select Stroke with a paint tool.
    • Set the drop-down menu to Airbrush.
    • Check the box for Emulate brush dynamics to apply the gradient transition properly along the vector.
  4. Click Stroke.

GIMP will trace the path from the initial node to the terminal node, applying the active gradient via the soft-edge Airbrush tool.