What's the best way to detect lines of a grid in an image?

I'm working on a project and I need to detect lines of a grid in an image captured by a camera or mobile of a Sudoku game.

I'm new to Matlab and I wish you give me some good advice. Thanks.

Answer 1

[Image Analyst]

Assuming the grid lines align with the image edges, I would sum the image horizontally and vertically and look for spikes.

horizontalProfile = sum(grayImage, 1); % Sum across all rows.
verticalProfile = sum(grayImage, 2); % Sum across all columns.

If the grid lines are rotated, then you'll have to use hough() or houghlines().