Straight Line Extraction Using Hough Transform

The Hough transform is a classical image processing technique used for detecting straight lines in images. Its core concept involves transforming lines from the image space to a parameter space (such as polar coordinates) and identifying the most probable line parameters through an accumulation voting mechanism. The algorithm works by representing each edge point in terms of possible lines passing through it, creating a voting accumulator where high-value bins correspond to dominant lines in the original image.

Implementing Hough transform for line extraction in MATLAB typically follows these steps with corresponding functions: Edge Detection: First, edge detection algorithms like Canny or Sobel are applied to obtain edge points from the image, as the Hough transform primarily relies on edge information. This is commonly implemented using MATLAB's `edge` function with specified parameters. Hough Transform Calculation: Using MATLAB's built-in `hough` function, edge points are mapped to the parameter space (ρ, θ), generating a Hough transform accumulator matrix. This function computes the distance (rho) and angle (theta) for all possible lines through each edge point. Peak Detection: The most significant peaks are identified in the accumulator matrix, corresponding to the strongest lines in the image. The current implementation extracts only the global maximum, but future improvements could include detecting local peaks using functions like `houghpeaks` with non-maximum suppression techniques. Line Drawing: Based on the detected (ρ, θ) parameters, the `houghlines` function reconstructs line segments in the image space, returning start and end points for each detected line.

Potential improvements include optimizing peak detection strategies (such as implementing non-maximum suppression) and introducing threshold controls to extract multiple lines while reducing noise interference. This method is suitable for applications like lane detection in autonomous vehicles, document layout analysis, and industrial inspection systems where robust line detection is required.