Drawing lines and perpendicular lines on a photo in MATLAB

I have a photo on MATLAB and I am using image processing. I have used circle detection to identify markers in a photo. I need to draw a line (e.g. line 1) to connect certain markers. I would then like to create a perpendicular line (e.g. line 2) at the mid section of line 1. Is it possible to do this on MATLAB?

I know there is the function 'imdistline' which can tell you the distance. I'm looking for something similar to this which can create a perpendicular.

Thank you

Answer 1

[KSSV]

YOu can draw perpendicular line for a given line as below:

%%Marker locations 
x = rand(1,2);
y = rand(1,2);
line(x,y)  % draw line 
%%Dra wpependicular line 
% Slope of current line
m = (diff(y)/diff(x));
% Slope of new line
minv = -1/m;
line([mean(x) mean(x)+0.5],[mean(y) mean(y)+0.5*minv],'Color','red')
axis equal

[Misha Patel]

can I do this on an image I read into maltab? at the moment it is only drawing it onto a graph in a figure

[KSSV]

Yes happily you can do that in image.....to do this in image...x and y should be your marker locations...I already mentioned as a comment.

[Misha Patel]

so do I just put the following before the code:

 image = imread('1.png');
imshow(image);

because it doesn't seem to appear... unless the line is just very small

[KSSV]

I = imread('peppers.png') ;

imshow(I) ;
hold on
[x,y] = getpts() ;
%%Marker locations 
% x = pts(:,1) ;
% y = pts(:,2);
line(x,y)  % draw line 
%%Dra wpependicular line 
% Slope of current line
m = (diff(y)/diff(x));
% Slope of new line
L = 50 ;
minv = -1/m;
line([mean(x) mean(x)+L],[mean(y) mean(y)+L*minv],'Color','g')
axis equal

When figure opens, pick any two points by clicking. You fix the value of L to get sufficient length of the line.

[Misha Patel]

that's very useful, thank you.

can I change the length of the perpendicular line so it is longer and extends either side of the original line (line 1). At the moment, the perpendicualr is only drawn to the right of the line, I want to be much longer and extend both left and right of the original line

[KSSV]

You can change L....instead of clicking you can use your coordinates, it is already shown in the code.

[hadis ensafi]

Hello.. thanks for your code.. I have this problem in 3D space! how can I calculate a perpendicular of a line in 3D space and in Specified plane? thanks a lot.