How to draw a line perpendicular to the medial axis in each point and save the intensity values?

Thats what I wrote to get the medial axis (skeleton). im=imread('gray.tif'); skelImg = bwmorph(im, 'skel', inf); figure; imshow(skelImg); hold on;

[Adam]

Please try to make the 'question' part as short and to the point as possible. The 'body' of the question is where you can put all the "Hi..." stuff. The question is there as a headline to direct people who have the knowledge to help to a thread and those who don't to by-pass it.

[Hamed Lamei Ramnadi]

sure

Answer 1

[Bruno Pop-Stefanov]

Take a look at the file overlayLines.m that I have attached. This function draws red lines over an RGB image. You can certainly modify it for a one-channel image. Also, if you examine the loop you'll see how to find the pixel values that the line crosses.

Example:

    I = imread('autumn.tif');
    x = [10,200;50,60];
    y = [140,160;20,200];
    J = overlayLines(I,x,y);
    imshow(J)

[Hamed Lamei Ramnadi]

Hi Bruno Thank you for your respond but it did not work out actually. Perhaps you did not get my point. I can draw lines by giving x and y. I need a code to draw these lines PERPENDICULAR to the medial axis in each point.

Cheers

Answer 2

[Radek]

Hi, i have solved same issue. my propasal is this (not the best and quickest solution ever but it works):

1. Calculate angle of the line

if true
  % code
Xdiff=X-Gpoint2X-GpointX;
  Ydiff=Gpoint2Y-GpointY;
  angle=tan(Ydiff/Xdiff);
end

Where Gpoint and Gpoint2 are two points on the line and GpointX is point G X coord

2. do

if true
angle=angle*(-1);
  % code
end

to make PERPENDICULAR line

3. use

if true
  function [Line LineIndexes]=ComputeLineCoords(angle,GpointX,GpointY, shift,L)
      X=size(L,2)
      StepElevation=tan(angle)*1
      Line(1:X)=round(StepElevation*(1:X)- GpointX*StepElevation  +GpointY+shift);

        OutOfboundsFromS=min(find(Line(1:X)<1))-1;

        OutOfboundsFromE=min(find(Line(1:X)>size(L,2)))+1;

        if (OutOfboundsFromS==1)
            LineIndexes=[OutOfboundsFromS];
        else
            if (OutOfboundsFromE==size(L,2))
                LineIndexes=[OutOfboundsFromE];
            else
                LineIndexes=[1];
            end
        end

        OutOfboundsToS=max(find(Line(1:X)>size(L,2)));

        OutOfboundsToE=min(find(Line(1:X)<1))-1;

        if (Line(OutOfboundsToE)<=1)
            LineIndexes=[LineIndexes OutOfboundsToE];
        else
            if (OutOfboundsToS>=X)
                LineIndexes=[LineIndexes OutOfboundsToS];
            else
                LineIndexes=[LineIndexes X];
            end
        end
  end

To get indexes of pixels in which the line is going (Line) and its bounding box in LineIndexes .

intputs are angle GpointX - Since i wrote it for XY you have to use Y coord of the point where the line should be placed GpointY - Since i wrote it for XY you have to use X coord of the point where the line should be placed shift - 0 should be fine but you hav eto experiment with it a little L - image to get sizes

you might play around a little with the dimensions but this worked for me