Wavelet Decompose for Architecture Cleanup in GIMP

This guide explains how to use the GEGL Wavelet Decompose filter in GIMP to perform non-destructive, high-precision architectural photo cleanup. By separating an image into distinct frequency layers (scales) and a base color layer (residual), you can isolate and remove distracting elements—such as power lines, sensor dust, graffiti, stains, and glare—without degrading fine masonry textures or natural surface gradients.

Understanding Wavelet Decompose in Architectural Editing

Wavelet Decompose splits an image into frequency bands. Fine details, such as concrete texture, sharp edges, and small scratches, are isolated onto the lower-numbered scale layers (e.g., Scale 1 and Scale 2). Broader transitions, like lighting gradients and large tonal shifts, reside on higher-numbered scale layers. The base color and overall illumination sit at the bottom on the "Wavelet Residual" layer.

This separation allows you to clone out a structural flaw or wire on a fine-detail layer without smudging the underlying sky gradient or paint tone. Conversely, you can smooth out uneven wall stains on the residual layer without blurring the crisp texture of the brick or stone.

Step 1: Prepare the Image and Run the Filter

  1. Open your architectural photo in GIMP.
  2. Duplicate the background layer to preserve your original image.
  3. Navigate to Filters > Enhance > Wavelet Decompose...
  4. In the dialog box, choose the number of Scales. A value between 5 and 7 is recommended for high-resolution architectural images.
  5. Check Create a layer group to keep the workspace organized.
  6. Click OK. GIMP will generate the grouped frequency layers, each set to the Grain Merge blending mode, along with the Wavelet Residual layer at the bottom.

Step 2: Removing Fine Distractions (Wires, Dust, and Scratches)

Power lines crossing clean facades, sensor spots in the sky, and fine scratches on metal or glass exist primarily on the lowest scale layers.

  1. Zoom in on the distraction.
  2. Toggle the visibility of Scale 1, Scale 2, and Scale 3 individually to identify which layer contains the unwanted object.
  3. Select the target scale layer in the Layers panel.
  4. Select the Clone Tool (C) or the Healing Tool (H). Ensure the tool's mode is set to Normal and the source sample is set to Current layer.
  5. Sample an adjacent, clean area on that same scale layer and paint over the distraction. Because you are only altering high-frequency data, the lighting and color underneath remain completely uniform.

Step 3: Correcting Tonal and Color Blemishes (Stains, Glare, and Patches)

Water stains, mismatched paint patches, or harsh reflections on flat surfaces often disrupt the clean lines of architectural spaces without altering surface texture.

  1. Select the Wavelet Residual layer or a higher-numbered scale layer (e.g., Scale 5 or Scale 6).
  2. Choose a soft-edged Paintbrush (P), the Smudge Tool (S), or the Clone Tool (C).
  3. Sample the correct color or smooth tone from an unaffected section of the wall.
  4. Gently paint or blend over the discoloration. The fine surface textures stored on Scales 1 through 3 will remain intact, preventing the surface from looking artificially smooth or blurry.

Step 4: Finalizing and Exporting

  1. Collapse the Wavelet Decompose layer group to verify your edits against the original image by toggling the group visibility on and off.
  2. If further global adjustments are needed, right-click the layer stack and select New from Visible.
  3. Export the final edited image via File > Export As... in your desired format.