Edge detection: gradients and Laplacian zero crossings

Sun, 11 Oct 2026 00:00:00 +0000

The same photograph can give quite different edge maps. For this BCV lab, I compared a gradient detector with a Laplacian zero-crossing detector. The teacher’s notebooks weren’t available, so these results come from an independent Python implementation.

Both methods start with grayscale conversion and Gaussian smoothing. The gradient pipeline uses Sobel derivatives, thinning and hysteresis. The Laplacian pipeline looks for sign changes in the filtered response. Small fragments are removed at the end.

Image Processing on WANG Zhaofeng · Course Portfolio

Edge detection: gradients and Laplacian zero crossings