How to Use Liquid Rescale in GIMP Without Distortion

The Liquid Rescale plugin in GIMP utilizes seam carving technology to intelligently resize images by removing or inserting pixels in less important areas, such as plain backgrounds. By setting up a protection mask over human subjects, you can scale an image's aspect ratio or overall dimensions horizontally and vertically while preserving the natural proportions of the people in the frame.

1. Prepare Your Image and Protection Layer

  1. Open your image in GIMP.
  2. In the Layers panel, click the New Layer button to add an empty, transparent layer above your base image. Name this layer "Protection Mask."
  3. Select the Paintbrush Tool (P) and pick any high-visibility color, such as bright green or red.
  4. Paint over the people or subjects you want to protect from distortion. You do not need pixel-perfect precision, but ensure the entire body and face of the subject are covered by the paint.

2. Launch the Liquid Rescale Dialog

  1. Select your original photo layer in the Layers panel.
  2. Go to the top menu and select Layer > Liquid rescale. If the plugin is installed correctly, the main configuration window will appear.

3. Assign the Protection Mask

  1. In the Liquid Rescale window, locate the Features preservation section.
  2. Check the box to enable feature preservation, or click the dropdown menu labeled Feature to preserve.
  3. Select the "Protection Mask" layer you painted earlier.
  4. Set the preservation strength. A value of 1000 or maximum ensures that the seam carving algorithm strictly avoids cutting seams through the masked people.

4. Optional: Set a Discard Mask

If there are specific empty areas you actively want the algorithm to remove first (such as blank sky or empty wall):

  1. Create another transparent layer named "Discard Mask."
  2. Paint over the unwanted background sections.
  3. In the Liquid Rescale dialog, select this layer under Feature to discard and assign it a high discard weight.

5. Adjust Dimensions and Run

  1. In the Target size section at the top of the dialog, input your desired Width and Height.
  2. Ensure the chain link icon is unlinked if you are changing the aspect ratio (for example, converting a wide landscape photo into a square format).
  3. Under the Output tab, choose whether you want the result to generate as a New layer or modify the active layer directly.
  4. Click OK to start the seam carving process.

Once the calculation finishes, hide or delete your temporary mask layers. Your subject will remain intact with original proportions, while the background shrinks or expands around them.