Edge Detection

Detect edges in your image with the Sobel operator to extract object outlines and create a black-and-white line-art effect. Adjust the threshold to control line density. All processing happens locally in your browser — your image is never uploaded.

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Drop an image or click to upload

PNG, JPG, WEBP, BMP

What Is the Edge Detection Tool?

The Edge Detection tool uses the Sobel operator to extract object outlines from your image, turning photos into black-and-white line art.

It's great for line-art illustrations, extracting design outlines, or as an artistic filter.

How to Extract Image Outlines

Follow these steps:

  • Drop or upload an image.
  • Adjust the threshold to control line density.
  • Click Detect Edges and preview the line art.
  • Download the line art as a PNG file.

Tips

  • A threshold of 30–80 usually works best.
  • High-contrast images produce clearer outlines.
  • Combine line art with the negative tool for an inverted white version.

Frequently Asked Questions

How does edge detection work?+
The tool uses the Sobel operator to compute the brightness gradient of each pixel in the horizontal and vertical directions. Pixels with large gradients are edges, and the result is a black-and-white line drawing.
What does the threshold mean?+
The threshold decides which gradients count as edges: lower thresholds detect more lines, while higher thresholds keep only the most obvious outlines.
What is it good for?+
You can create line-art style images, extract object outlines for design reference, or use it as a sketch-style artistic filter.
Is my image uploaded anywhere?+
No. All processing happens locally in your browser — your image never leaves your device.

Related Tools

Oil PaintNegative/InvertPixelate/Mosaic

Edge Detection — free online edge detection, line art, outline extraction, sketch effect, sobel, photo to line art, extract outlines. No signup required. Works in your browser.