Sobel Edge Detection Online Detect and highlight edges using Sobel operator convolution.

What Is Image Edge Detect?

Uses the Sobel operator with horizontal and vertical 3x3 kernels to detect edges, producing white edges on black background.

Why Use Image Edge Detect?

• Sobel operator for accurate detection
• Adjustable threshold
• Clean line-art output
• Foundation for image analysis

Common Use Cases

Line Art

Extract drawings from photos.

Image Analysis

Identify boundaries and contours.

Design Effects

Neon glow or wireframe effects.

Coloring Pages

Generate outlines from photos.

Technical Guide

Sobel kernels: Gx=[[-1,0,1],[-2,0,2],[-1,0,1]], Gy=[[-1,-2,-1],[0,0,0],[1,2,1]]. Magnitude = sqrt(Gx²+Gy²), thresholded.

Tips & Best Practices

• 1
  Lower threshold for more edges
• 2
  Smooth noisy images first
• 3
  Invert for dark edges on white
• 4
  Convert to grayscale first

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Frequently Asked Questions

Q Why black and white?

Edge detection shows edge strength as brightness. Color is not relevant.

Q What is Sobel?

A pair of 3x3 kernels detecting horizontal and vertical gradients.

Q How does threshold work?

Filters edges below a certain strength.

Q Can I detect edges in color images?

Converts to grayscale first for edge computation.

About This Tool

Image Edge Detect is a free online tool by FreeToolkit.ai. All processing happens directly in your browser — your data never leaves your device. No registration or installation required.