Hands-On Image Processing with Python

Hough transform – detecting lines and circles

In image processing, Hough transform is a feature extraction technique that aims to find instances of objects of a certain shape using a voting procedure carried out in a parameter space. In its simplest form, the classical Hough transform can be used to detect straight lines in an image. We can represent a straight line using polar parameters (ρ, θ), where ρ is the length of the line segment and θ is the angle in between the line and the x axis. To explore (ρ, θ) parameter space, it first creates a 2D-histogram. Then, for each value of ρ and θ, it computes the number of non-zero pixels in the input image that are close to the corresponding line and increments the array at position (ρ, θ) accordingly. ...