How to Create Anaglyph 3D Images in GIMP

Creating anaglyph stereoscopic 3D images in GIMP is a straightforward process that transforms two offset photographs into a single image viewable with standard red-cyan 3D glasses. This guide walks you through preparing your left and right source images, isolating the specific color channels for each eye, blending the layers together, and aligning the focal points to achieve a clean, immersive 3D effect.

Step 1: Prepare Your Stereo Pair

To create a true 3D effect, you need two separate images of the same subject:

  1. Left Image: A photo taken from the left perspective.
  2. Right Image: A photo taken approximately 2.5 inches (the distance between human eyes) to the right of the first photo, focused on the exact same subject.

Step 2: Open the Images as Layers

  1. Open GIMP.
  2. Go to File > Open as Layers...
  3. Select both the left and right images and click Open.
  4. In the Layers panel on the right, rename the top layer to Left and the bottom layer to Right to avoid confusion.

Step 3: Filter the Left Image (Red Channel)

  1. Select the Left layer in the Layers panel.
  2. Navigate to Colors > Levels... in the top menu.
  3. In the dialog box, find the Channel dropdown menu (which defaults to "Value").
  4. Select the Green channel, then drag the Output Levels right slider (white point) all the way to 0.
  5. Select the Blue channel, then drag the Output Levels right slider all the way to 0.
  6. Leave the Red channel untouched and click OK. The left image will now appear entirely red.

Step 4: Filter the Right Image (Cyan Channel)

  1. Select the Right layer in the Layers panel.
  2. Navigate to Colors > Levels...
  3. In the Channel dropdown, select the Red channel.
  4. Drag the Output Levels right slider all the way to 0.
  5. Leave the Green and Blue channels untouched and click OK. The right image will now appear cyan (blue-green).

Step 5: Blend the Layers

  1. Select the top layer (Left).
  2. At the top of the Layers panel, change the Mode dropdown from Normal to Screen (or Addition).
  3. The two layers will merge, restoring the original colors of the scene while creating visible red and cyan fringes along the edges of objects.

Step 6: Align the Focal Point (Convergence)

  1. Put on your red-cyan 3D glasses (red lens over the left eye, cyan lens over the right eye).
  2. Select the Move Tool (M on your keyboard).
  3. Click on the top layer and use the arrow keys on your keyboard to shift it left or right.
  4. Align the primary subject of your photo until the red and cyan fringing on that specific object overlaps as closely as possible. Objects in front of or behind this focal point will naturally maintain separation, creating depth.

Step 7: Crop and Export

  1. Select the Crop Tool (Shift + C).
  2. Draw a box around the usable area of the image to remove the uneven edges caused by shifting the layers.
  3. Press Enter to apply the crop.
  4. Go to File > Export As..., choose your preferred format (such as .jpg or .png), and click Export.