Stamp Brush

A clone-stamp brush extension for Aseprite — select a source area and paint with it like a stamp. With tiled canvas, smoothstep brush mask, max-alpha blending, pan/zoom, selection masking, and local undo/redo.

2026-06-26.03-35-46.mp4

📜 Table of contents

• Features
• How to install
• How to use
• Controls
• FAQ

🎯 Features

• Clone-stamp brush — paint by sampling color from any part of a cel or its tiled copies.
• Soft brush — smoothstep brush mask with adjustable radius (1-64), softness, and opacity.
• Tiled canvas — display 1×1, 3×1, 1×3, or 3×3 tiles with boundary lines. Tiling works as both a visual reference and a source-wrapping mode.
• Max-alpha accumulator — no blending artifacts on overlapping strokes. Each stroke collects the maximum alpha per pixel and flushes once.
• Pan and zoom — middle-click drag to pan, mouse wheel to zoom (powers of two: 0.5× to 32×). Pinch-to-zoom on trackpad is not supported.
• Selection masking — the brush only paints inside the active selection. Selection outline is rendered with marching-ants-style alternating colors via BlendMode.DIFFERENCE for visibility on any background.
• Dynamic preview — see what will be painted before you click, updated in real time.
• Stamp spacing — stamps are interpolated along mouse movement with configurable spacing (25% of radius) for smooth strokes.
• Local undo/redo — Ctrl+Z / Ctrl+Shift+Z with full stroke history. Redo history is cleared on new strokes. Keyboard shortcuts are handled by the canvas widget — they may not work if the canvas loses focus. Click the canvas to restore focus.
• Continue editing — save your work, discard, or continue editing if you close the dialog accidentally.
• Auto-expanding cel — when painting outside the cel bounds, the cel automatically grows to include new pixels. Works exactly like Aseprite's native PatchCel command.
• Source snapshot — clone source is captured from the current cel state. Updated after each stroke and on undo/redo, so you can clone from your own modifications.
• Full-window dialog — opens to fill the entire Aseprite window for maximum workspace.
• Auto-zoom — initial zoom level is automatically calculated to fit the content in the available canvas area.
• Fixed canvas size — workImg is the full sprite canvas. The cel is drawn onto it at its position. Painting happens in absolute canvas coordinates — no mid-stroke image expansion needed.

💽 How to install

1. Download the .aseprite-extension file from the Releases page.
2. Double-click the file, or install via Edit > Preferences > Extensions > Add Extension.
3. The "Clone Stamp" command will appear in the Edit menu. You can assign a keyboard shortcut via Edit > Keyboard Shortcuts — search for "Edit > Clone Stamp".

Alternatively, clone this repository and copy the folder to your Aseprite extensions directory:

• macOS: ~/Library/Application Support/Aseprite/extensions/
• Windows: %AppData%/Aseprite/extensions/
• Linux: ~/.config/aseprite/extensions/

👷 How to use

1. Open an image in Aseprite and select the cel you want to modify (if it is not selected yet).
2. (Optional) Make a selection if you want to paint only within specific bounds.
3. Run Edit > Clone Stamp.
4. Left-click or Right-click on the area you want to clone FROM (sets the source point).
5. Left-click and drag to paint with the clone stamp.
6. Right-click to set a new source point (captures the current canvas state, including your previous strokes).
7. Use sliders to adjust Tiled Mode, Radius, Opacity, and Softness.
8. Close the dialog — choose Apply to commit changes, Discard to cancel, or Continue Editing to keep working.

Mouse controls

Action	Button
Set source point	Left click (only first time) or Right click (always)
Paint	Left click and drag
Cancel stroke	Right click while drawing
Pan	Middle click and drag
Zoom	Mouse wheel (powers of two)
Brush size	Shift + mouse wheel

Keyboard controls

Action	Shortcut
Undo	Ctrl+Z (Cmd+Z on macOS)
Redo	Ctrl+Shift+Z or Ctrl+Y (Cmd+Shift+Z or Cmd+Y on macOS)
Apply and close	Enter

❓ FAQ

The brush doesn't paint outside the cel

Make sure Tiled Mode is set to Both (value 3). In other modes, source wrapping is disabled in one or both directions.

Keyboard shortcuts and Shift+scroll don't work

Keyboard events (undo/redo, Shift+scroll) are only received by the canvas widget, not the whole dialog. If the canvas loses focus — e.g., after an app.alert popup or clicking outside the canvas — these stop working. Click anywhere on the canvas to restore focus. This is a limitation of the Dialog canvas API architecture.

Shift+scroll changes brush size unpredictably (macOS)

If Shift+scroll doesn't change brush size, or the size changes disproportionately (e.g., only decreases), and you use Linear Mouse on macOS — set Scrolling Mode to By Pixels and all Modifier Keys to Default Action.

The dialog opens too small

The dialog is set to fill the entire Aseprite window on open. If it appears small, try resizing it manually — the next session will remember the size.