How to Create 3D Anaglyph Images in GIMP

Creating a 3D red-cyan anaglyph image in GIMP involves capturing two offset photographs, aligning them as separate layers, and isolating specific color channels to merge the perspectives. By mapping the red channel from the left-eye view and the green and blue (cyan) channels from the right-eye view into a single composite, you can produce a classic stereoscopic effect viewable with standard 3D glasses.

Step 1: Capture and Load the Image Pair

  1. Take two photos of a static subject: a "Left" image and a "Right" image. Shift the camera horizontally about 2.5 inches (the average distance between human eyes) between shots without tilting.
  2. Open GIMP.
  3. Go to File > Open as Layers... and select both the Left and Right images.
  4. Rename the layers in the Layers panel to Left and Right to avoid confusion. Ensure the Right layer is on top of the Left layer.

Step 2: Align the Subject

  1. Select the top layer (Right) and temporarily reduce its Opacity to roughly 50% in the Layers panel.
  2. Select the Move Tool (shortcut: M) and shift the Right layer so your main subject overlaps cleanly with the subject in the Left layer. This overlap point becomes the focal plane (zero parallax).
  3. Return the Right layer opacity to 100%.

Step 3: Isolate Color Channels

  1. Go to Colors > Components > Decompose...
  2. In the dialog, set the Color model to RGB and check "Decompose to layers." Click OK. This creates a new temporary grayscale image containing Red, Green, and Blue layers for your top image. Repeat this step for the other view if working from separate files, or proceed via layer-based channel extraction.
  3. Alternatively, use the direct composition method: go to Colors > Components > Compose...
  4. Set the Color model to RGB.
  5. Map the channels as follows:
    • Red: Select the Left image layer.
    • Green: Select the Right image layer.
    • Blue: Select the Right image layer.
  6. Click OK. GIMP will automatically generate a new RGB image combining the red spectrum of your left perspective with the cyan spectrum of your right perspective.

Method B: Using Color Curves / Levels

  1. Select the Left layer. Go to Colors > Levels..., select the Green channel, and set the Output High level to 0. Select the Blue channel and set the Output High level to 0. Click OK (the image will appear purely red).
  2. Select the Right layer. Go to Colors > Levels..., select the Red channel, and set the Output High level to 0. Click OK (the image will appear cyan).
  3. In the Layers panel, set the blending mode of the top layer (Right) to Screen or Addition.

Step 4: Crop and Export

  1. Because the layers were shifted horizontally during alignment, transparent or misaligned borders will appear on the edges.
  2. Select the Crop Tool (shortcut: Shift + C) and crop the image to remove the uneven borders.
  3. Go to File > Export As..., choose your desired file format (e.g., JPEG or PNG), and save the final 3D anaglyph image.