Image Edge Detect 〰️
Detect edges in images using the Sobel operator. Adjust sensitivity to control how strong edges appear.
Click to browse or drop an image here
JPG, PNG, WebPAbout the Image Edge Detect tool
The Image Edge Detect tool runs entirely in your browser. Drop or select an image, set the Sensitivity slider, and click Apply. The image is first converted to grayscale using the luminance formula 0.299R + 0.587G + 0.114B. For each interior pixel, the tool applies the Sobel operator with kernels Gx = [-1,0,1,-2,0,2,-1,0,1] and Gy = [-1,-2,-1,0,0,0,1,2,1] over a 3×3 neighborhood, then computes the gradient magnitude sqrt(gx² + gy²). The magnitude is scaled by the sensitivity factor and clamped to 0–255, producing a grayscale edge map where edges appear bright and flat regions appear dark. Nothing is uploaded; all processing happens locally.
How to use it
- Click the drop zone or drop an image file onto it.
- Drag the Sensitivity slider — higher values produce brighter, more pronounced edges.
- Click Apply to render the edge map onto the canvas.
- Click Download to save the result, Reset to restore the original, or Clear to start over.
Frequently asked questions
What does the sensitivity control? It scales the gradient magnitude. 100% uses the raw Sobel output; lower values produce subtler, dimmer edges; values above 100% amplify faint edges but may introduce noise.
Why are the image borders dark? The Sobel operator needs a 3×3 neighborhood, so the outermost 1-pixel border cannot be computed and is set to black.
What is the output format? The download is a PNG file. This preserves detail and avoids compression artifacts.
Does this tool upload my images? No. All processing happens locally in your browser. Your image never leaves your device.