Create a Stained Glass Window in GIMP

Transforming a standard digital image into a simulated stained glass window is a straightforward process in GIMP using built-in distortion filters and color adjustments. This guide walks you through the step-by-step method of preparing your base image, applying the Mosaic filter to generate segmented glass tiles and leaded outlines, enhancing color saturation, and adding a subtle backlight glow to replicate sunlight shining through colored glass.

Step 1: Prepare Your Base Image

  1. Open GIMP and load the image you want to convert by going to File > Open.
  2. Images with strong contrasts, bold subjects, and distinct color regions produce the best stained glass results.
  3. In the Layers panel on the right, right-click the background layer and select Duplicate Layer to preserve your original artwork.

Step 2: Apply the Mosaic Filter

  1. Select the duplicated layer.
  2. Navigate to Filters > Distorts > Mosaic.
  3. In the Mosaic dialog window, adjust the following settings to create the segmented glass effect:
    • Tile geometry: Set to Hexagons, Octagons & squares, or Triangles based on your preference (Triangles or Hexagons often provide the most traditional stained glass appearance).
    • Tile size: Increase or decrease the slider depending on the resolution of your image and how large you want individual glass segments to be.
    • Tile height: Increase slightly (around 5 to 10) to give the tiles a slightly beveled, three-dimensional look.
    • Tile spacing: Adjust to set the width of the lead solder lines between the glass pieces (usually between 2 and 5 pixels).
    • Joints color: Ensure this is set to black or dark charcoal to simulate traditional lead framing.
    • Light direction: Adjust the light angle to match the natural light direction of the image.
  4. Click OK to apply the filter.

Step 3: Enhance Vibrancy and Contrast

  1. Stained glass relies on rich, saturated light. Go to Colors > Hue-Saturation.
  2. Increase the Saturation slider to make the colors vibrant.
  3. Go to Colors > Curves or Colors > Levels.
  4. Increase the contrast slightly by pulling the darks lower and the highlights higher. This step sharpens the separation between the bright glass sections and the dark lead joints.

Step 4: Add Glass Texture (Optional)

  1. Go to Filters > Noise > CIE lch Noise or Filters > Noise > HSV Noise.
  2. Add a very subtle amount of noise to the layer to mimic imperfections, bubbles, and grain found in real antique glass.
  3. Keep the noise values low so the texture does not overwhelm the subject.

Step 5: Simulate Backlighting and Glow

  1. Duplicate the mosaic layer.
  2. On the top layer, go to Filters > Blur > Gaussian Blur.
  3. Set the blur radius between 10 and 20 pixels, then click OK.
  4. Change the top layer's Mode in the Layers panel to Screen or Soft Light.
  5. Lower the layer Opacity to around 30%–50% until the light appears to naturally diffuse through the colored panes without washing out the dark outlines.