Adjust Stroke Density in GIMP Oilify Filter

The GIMP Oilify filter transforms images into digital paintings by grouping pixels into simulated brushstrokes. This guide explains how to control stroke density and surface texture using the Mask size and Exponent sliders. By mastering the relationship between these two parameters, you can precisely dictate whether your final artwork features fine, intricate details or broad, heavy paint strokes.

Accessing the Filter

To open the tool, navigate to Filters > Artistic > Oilify... from the top menu bar in GIMP. Ensure the preview box is checked so you can observe real-time changes while adjusting the values.

Understanding the Sliders

  • Mask Size: Controls the radius of the pixel neighborhood used to calculate the stroke. In practical terms, this defines the physical dimensions of each brushstroke.
  • Exponent: Dictates the weighting applied to the most common pixel color within that mask. It effectively controls the sharpness, contrast, and density distribution of the applied paint.

How to Alter Stroke Density

Stroke density refers to how tightly packed, distinct, and detailed the simulated paint marks appear across the canvas. You can shape this density using specific combinations of both sliders:

1. Creating High Stroke Density (Fine, Detailed Strokes)

To create an image packed with dense, fine strokes that preserve the underlying subject's edges and features:

  • Reduce the Mask Size (e.g., 3 to 8): A smaller radius confines the filter to smaller pixel clusters, generating high-frequency, smaller marks.
  • Increase the Exponent (e.g., 10 to 20): A higher exponent forces the algorithm to heavily prioritize dominant local colors. This hardens the edges of each small stroke, preventing them from bleeding together into a blurry smudge and creating a dense, crisp network of paint marks.

2. Creating Low Stroke Density (Broad, Expressive Strokes)

To achieve an abstract, heavy impasto style with fewer, larger brush marks:

  • Increase the Mask Size (e.g., 15 to 35+): A larger mask samples wider areas, reducing the total count of individual strokes and expanding their footprint.
  • Lower the Exponent (e.g., 2 to 6): A lower exponent produces softer transitions between the larger strokes. This flattens fine textures into broad patches of color, mimicking a large, loaded brush sweeping across the canvas.
  1. Set the Exponent to a baseline value of 8.
  2. Adjust the Mask size until the strokes match the physical scale appropriate for your image resolution.
  3. Fine-tune the Exponent: raise it if the image looks too muddy or soft, or lower it if the strokes appear overly harsh and pixelated.