Edge Detection

What is edge detection?

Every image is made up of places where tone changes sharply and places where it stays smooth. This tool finds those sharp transitions and draws them as dark lines against a white background, making the edges and contours of your subject visible on their own. It is useful for studying where the strong boundaries in a reference are, checking whether a composition reads as a clear set of shapes, or understanding the underlying structure of a painting.

How to use this tool

1. Upload an image. Drop a photo or painting onto the canvas, or click to browse. HEIC files from iPhone are supported.
2. Read the result. White areas are smooth and tonally even. Dark lines are edges — places where tone shifts sharply, marking a boundary, contour, or form change in the image.
3. Adjust Threshold. Lower values show more edges, including subtle tonal shifts and fine texture. Higher values keep only the boldest, most prominent boundaries.
4. Adjust Smoothness. Softens the image before detecting edges, which filters out small details like grain or individual brushstrokes. Raise it when you want only the major shapes and contours.
5. Adjust Opacity. Blends the result back over the original so you can see which edges belong to which part of the image.
6. Compare and download. Hold the "Hold to compare" button to toggle back to the original. Download a full-resolution PNG when you are done.