Set GIMP Dynamic Brush Pressure for Color Mixing

Controlling how colors blend based on stylus pressure allows for seamless transitions and natural painterly effects in GIMP. This guide explains how to create a custom Paint Dynamic, map stylus pressure to the color matrix, and configure your brush tool options to adjust color mix ratios on the fly.

Step 1: Open the Paint Dynamics Editor

  1. Open GIMP and navigate to the top menu.
  2. Select Windows > Dockable Dialogs > Paint Dynamics.
  3. In the Paint Dynamics dock, click the Create a new dynamic icon (the blank page at the bottom).
  4. The Paint Dynamics Editor will open automatically. Name your new dynamic (e.g., "Pressure Color Mix").

Step 2: Map Pressure to Color

  1. In the Paint Dynamics Editor matrix, locate the Pressure column along the top.
  2. Locate the Color row along the left side.
  3. Check the box at the intersection of the Pressure column and the Color row. This links the pressure applied to your graphics tablet directly to color progression.

Step 3: Configure Tool Options for Color Dynamics

  1. Select the Paintbrush tool from the Toolbox.
  2. In the Tool Options dock, expand the Dynamics section and select the custom dynamic you created in Step 1.
  3. Scroll down to the Color Options section in the Tool Options dock:
    • Expand Color Options and check the box if it is collapsed.
    • Choose a gradient or set the mode to blend between your Foreground and Background colors.
    • Under the gradient settings, select Color from Gradient or choose a two-color gradient (Foreground to Background).

Step 4: Fine-Tune the Pressure Curve (Optional)

  1. Return to the Paint Dynamics Editor.
  2. Click the Color tab (or the dynamic curve tab next to the matrix).
  3. Adjust the curve graph to alter the mix ratio:
    • A straight diagonal line produces a linear 1:1 mix ratio from the primary color to the secondary color based on pressure.
    • An S-curve provides sharper transitions between colors, while an arched curve requires heavier pressure to introduce the secondary color.

Now, applying light pressure applies the start of your color range (such as your foreground color), and increasing pressure gradually blends into the end color (such as your background color).