Simulate an Oil Painting in GIMP Using G'MIC Plugin

This guide provides a straightforward method for transforming digital photographs into realistic oil paintings using GIMP and the G'MIC (GREYC's Magic for Image Computing) plugin. You will learn how to set up your image layers, select the most effective artistic filters within G'MIC, adjust brush stroke and texture settings, and apply finishing touches to achieve an authentic canvas aesthetic.

Step 1: Prepare Your Image in GIMP

  1. Open your target image in GIMP by navigating to File > Open.
  2. Duplicate the base image layer by right-clicking it in the Layers panel and selecting Duplicate Layer (or pressing Shift + Ctrl + D). Name this layer "Oil Base".
  3. Right-click the duplicated layer and select Duplicate Layer once more to create a backup for blending. Name the top layer "Oil Effect".

Step 2: Open the G'MIC-Qt Plugin

  1. Select the "Oil Effect" layer in the Layers panel.
  2. Go to the top menu and select Filters > G'MIC-Qt.
  3. In the search bar at the top of the G'MIC interface, you can search for specific painting filters or expand the Artistic category.

Step 3: Apply the Primary Painting Filter

G'MIC contains several filters capable of simulating oil paintings. The two most effective options are Painting and Kuwahara.

Option A: The "Painting" Filter (Best for general brushwork)

  1. In the G'MIC search bar, type Painting and select the filter located under Artistic > Painting.
  2. Adjust the Brush Size (or Radius) to define the thickness of the strokes. Smaller values preserve fine details, while larger values create broad, impressionistic strokes.
  3. Adjust the Smoothness slider to blend adjacent color tones together, mimicking wet paint blending.
  4. Set the Output Layers option at the bottom to In place or New layer(s).
  5. Click Apply to preview the result.

Option B: The "Brushify" Filter (Best for distinct bristle strokes)

  1. Search for Brushify under Artistic > Brushify.
  2. Set the Number of Strokes according to the level of detail required (higher values yield more detail).
  3. Choose a brush shape preset (such as flat or round bristle) from the drop-down menu.
  4. Adjust the Paint Thickness to simulate impasto-style raised paint.

Step 4: Add Canvas and Impasto Texture

To make the oil effect convincing, add tactile surface relief.

  1. While still inside G'MIC, search for Engrave or Texturize.
  2. Alternatively, apply the G'MIC filter Artistic > Relief to simulate the lighting and shadows cast by thick oil paint strokes.
  3. Adjust the Angle and Depth parameters to match the light source of your original scene.
  4. Click OK to render the effect and return to the main GIMP workspace.

Step 5: Final Layer Blending and Color Grading

  1. In the GIMP Layers panel, select the "Oil Effect" layer.
  2. If the effect appears too harsh, lower the Opacity slider to between 85% and 95% to allow some fine photographic detail from the layer below to show through.
  3. To enhance the richness typical of oil paints, go to Colors > Curves or Colors > Hue-Saturation and slightly increase the contrast and color saturation.
  4. Go to File > Export As to save your final artwork in your preferred format.