Overtrace

Put a reference image over your paint app and trace it directly.

Overtrace shows a reference image semi-transparently, always on top of your paint program. In click-through mode your mouse and pen go straight to the app underneath, so you can trace naturally while looking at the reference.
The menu (toggle edit mode, settings, etc.) opens from the tray icon's right-click menu, or by right-clicking the image itself while in edit mode.

1Getting started

Launch Double-click Overtrace.exe. No installation needed — it is a single exe.
Choose a reference image After a short welcome message, a file dialog opens. Pick the image you want to trace (JPG / PNG / BMP / GIF / WebP). A small cat animation with “Loading image…” is shown while it loads. If you close the dialog without choosing an image, the app quits.
※ From the second launch on, the last image is restored with its previous position, size and tilt, so you can continue where you left off. Use “Open image...” in the menu to switch to a different image.
※ To overlay several reference images at once, launch the exe again. The second and later instances start with the file dialog. You can tell which window is which by the filename tag at the top-left of the frame in edit mode, or by the first line of the right-click menu. Placement is remembered per image.
Adjust size and tilt with the 8 handles Drag the round handles at the corners and the square handles in the middle of each edge. Hover a handle to see what it does.
- Drag: scale, keeping the aspect ratio (opposite corner fixed)
- Shift + drag: scale width and height independently
- Ctrl + drag: move only that corner — perspective / keystone correction (e.g. a photo taken at an angle)
- Alt + drag: scale around the center, keeping the aspect ratio
Square handles on the edges
- Drag: move that edge perpendicularly — changes only width or height (opposite edge fixed)
- Shift or Alt + drag: the opposite edge moves too (symmetric around the center)
- Ctrl + drag: move the edge freely (shear into a parallelogram)
Undo / Redo Ctrl + Z goes back one step (also in the tray menu). Ctrl + Y redoes it. Flips and reset can be undone too.
Fine adjustment with keyboard and wheel Arrow keys move 1 px (Shift: 10 px). The mouse wheel scales around the center, Ctrl + wheel rotates 1° per notch, and Esc returns to click-through mode.
Replacing the image Besides “Open image...” in the menu, you can drop an image file onto the reference in edit mode, or paste a copied image with Ctrl + V (images copied from a web browser work too).
Rotating Drag the dark green round handle that sticks out above the top edge. The image rotates around its center; hold Shift to snap to 15° steps.
※ When the image is very small, the edge handles are hidden so they don't overlap the corner handles.
Opacity Right-click the tray icon and use the “Opacity” slider or number box in the menu. Opacity is remembered per image.

2Using it with your paint app

Start your paint app first and prepare the canvas.
Position the reference using the steps above.
Switch to click-through mode — click the tray icon or press Ctrl + Alt + T. Mouse and pen input now goes to the paint app.
Trace — just draw along the lines in your paint app.
Back to edit mode when needed — click the tray icon or press Ctrl + Alt + T again.

3Tray menu

Item	What it does
Toggle edit mode	Switch between click-through and edit mode (`Ctrl+Alt+T` also works)
Open image...	Replace the reference image
Reset position and shape	Center the image and restore a plain rectangle
Flip horizontally / vertically	Mirror the reference
Undo / Redo	Step back / forward (`Ctrl+Z` / `Ctrl+Y`)
Opacity	Slider or number box (0–100 %)
Display on monitor	Choose the monitor for the reference (shown only with two or more monitors; remembered)
Show in system tray only	When checked, the window has no taskbar button (off by default)
Show welcome message at startup	Show the welcome message again on the next launch
Language / 言語	Switch the UI language between Japanese and English
Reset all settings...	Clear all saved settings and restore the defaults (the current image stays)
Help	Open this page
Visit Septentrion's website ↗	Open the official site in your browser
Quit	Exit the app

4FAQ

The reference drifts when I scroll or zoom my paint app

The reference is overlaid at a fixed screen position; it does not follow the canvas. Keep the paint app's zoom and scroll fixed while tracing, or re-align the reference in edit mode.

Ctrl+Alt+T does nothing

If another app already uses that key, Overtrace automatically falls back to Ctrl+Alt+Shift+T (then Ctrl+Shift+T) and tells you in a notification. The key actually in use is shown next to “Toggle edit mode” in the menu. If none could be registered, click the tray icon instead. No administrator rights are needed.

Windows says “Windows protected your PC”

Click “More info” → “Run anyway”. This is the standard SmartScreen warning for unsigned apps from individual developers.

Does it support multiple monitors?

Yes. With two or more monitors, “Display on monitor” appears in the tray menu. If the chosen monitor is disconnected, the primary monitor is used.

The app closed unexpectedly

Unhandled errors are written to %LOCALAPPDATA%\Septentrion\Overtrace\overtrace.log. Please attach this file when reporting a problem.

Where are settings stored?

Opacity, the last images and their placement are stored in the registry under HKEY_CURRENT_USER\Software\Septentrion\Overtrace; pasted images are saved in AppData\Local\Septentrion\Overtrace. To uninstall, just delete the exe (and optionally that registry key).

5Requirements

Windows 10 / 11 (64-bit)
No installation, no additional libraries, no administrator rights
Free (donations welcome)

6Website

https://septentrion18.com

If Overtrace helps you, you can buy me a coffee on Ko-fi (also from "Support development (Ko-fi)" in the right-click menu):
https://ko-fi.com/septentrion