Sobel - Quick Cheat Sheet

• What it does: Highlights intensity changes (edges) by convolving the image with horizontal/vertical 3x3 kernels.
• Kernels:

Gx = [-1  0  1 -2  0  2 -1  0  1]

Gy = [-1 -2 -1 0  0  0 1  2  1]

• Magnitude: |∇I| = sqrt((Gx * I)^2 + (Gy * I)^2) (this tool clamps to 0-255).
• Grayscale first: Recommended. Uses 0.2126R + 0.7152G + 0.0722B for luminance.
• Threshold: 0 shows raw magnitudes. Higher values (e.g., 128/200) produce cleaner, binary edges.
• Local only: Everything runs in your browser; images aren't sent to a server.
• Tip: Very large images can be slow; consider resizing before processing.