How to Use the Cage Transform Tool in GIMP

The Cage Transform tool in GIMP allows you to warp, stretch, and reshape specific areas of an image by building a custom polygonal cage around your subject. By creating anchor points along the contours of a subject, you generate a multi-point deformation mesh that recalculates and bends the underlying pixels when points are repositioned. This guide explains how to set up your image, construct a multi-point deformation mesh, manipulate vertices, and apply your final transformation efficiently.

1. Select the Cage Transform Tool

Open your image in GIMP and ensure the target layer is selected in the Layers panel. Activate the Cage Transform tool using one of the following methods:

  • Go to the top menu and select Tools > Transform Tools > Cage Transform.
  • Click the Cage Transform icon in the Toolbox (it resembles an outlined polygon with handles).
  • Press the keyboard shortcut Shift + G.

2. Configure the Tool Options

Look at the Tool Options dockable dialog (typically on the left side under the Toolbox). Under the Cage Transform settings, you will see two main modes:

  • Create or adjust the cage: Used for plotting and repositioning your anchor points to define the mesh.
  • Deform the cage to produce the image: Used for moving the points to warp the graphic.

Ensure Create or adjust the cage is selected before you begin plotting points. You can also toggle the Fill the original position of the cage with a plain color option depending on whether you want transparency or a solid fill left behind when pixels are stretched.

3. Build the Deformation Mesh

To construct the cage around your target area:

  1. Place the initial point: Left-click on the canvas near the boundary of the object you want to distort.
  2. Add surrounding points: Continue clicking along the perimeter of the object to place additional nodes. For smooth, organic deformations (such as limbs, fabric, or faces), place points closer together around joints and curves. For broad adjustments, fewer points are sufficient.
  3. Close the mesh: Hover over the very first point you created until it highlights, then left-click it. This connects the final segment and closes the cage, which establishes the deformation mesh.

4. Adjust the Mesh Before Deforming

If any points are misplaced after closing the cage:

  • While still in Create or adjust the cage mode, click and drag any existing point to fine-tune its position along your subject's outline.
  • To add an extra point along an existing edge, click directly on the segment between two existing nodes.

5. Deform the Image Using the Mesh

Once your mesh accurately encompasses the target area, you are ready to deform the pixels:

  1. In the Tool Options dialog, switch the mode to Deform the cage to produce the image (GIMP usually switches to this automatically once the cage is closed).
  2. Click and drag any point on the mesh. GIMP will recalculate the pixels inside the cage and stretch or compress them based on the new point coordinates.
  3. To move multiple points at the same time, hold Shift and click each point you wish to select, then drag one of the selected points to move the entire group together.

6. Commit the Transformation

When you are satisfied with the deformation, press Enter on your keyboard to render and commit the changes to the active layer. To cancel the operation at any time prior to pressing Enter, select another tool from the Toolbox or press Esc.