Hough transformation and Detecting parallel lines

how can i compare edge of a rectangle with a theoretical line straight line and see if they are parallel and if they are not i want to rotate the rectangle until the side of it is parallel to the line. should i use hough transformation or what method best suites this application. Thank you.

Answer 1

[Nitin]

I = imread('rectangle.jpg');

I2 = rgb2gray(I);

%Get the 2 lines

I3 = I2 > 60 & I2 < 75;

% Clean image

I4 = bwareaopen(I3,20);

%Search for lines in image and estimate angle between them using Hough