How to measure lengths of edges in edge-detected images?

I want to get the boxes count in a warehouse by using 开发者_JAVA技巧image processing edge detection techniques. So I used Sobel algorithm to detect edges. Now I need to measure the edge length. Does anyone know how to get length of edges and any suitable algorithm to get final count ?

---

You can consider using Canny Edge Detector that extracts edges. All edge points have the width of one pixel. Then you can extract the connected components of edge points and count how many pixels are in each connected component.

---

You should consider using the Hough transform for identifying the boxes. The basic transform won't explicitly give you the length of the side of a particular box however, but it would be a good starting point.

Take a look at Localization of Piled Boxes by Means of the Hough Transform.