How to make traversal in an image and change color of the specified pixels along the path by some criteria, for example in my image i shown as under, I want to place after each five pixels a white pixel in an image.?

[KALYAN ACHARJYA]

Pls, clarify Here you want to replace the pixel with a white pixel or add new pixel. If you add then the size of the image will change.

[Mohammad Bhat]

Hi, I want to replace.....

[Image Analyst]

It's not clear, for a general blob, or even for a skeleton with some branches, what "every fifth pixel" means. It's ambiguous. WHY do you want, or need, to do this anyway?

[Mohammad Bhat]

hi, Actually I want to extract underlying graph from handwritten word image.As shown in figure , i have extracted branch and end points. To represent whole image in an exact manner, I want to add nodes or after regular intervals along the path.So that we get better reprentation intetms of nodes.

[Mohammad Bhat]

1. find start and end points. 2. find branch or junction points. 3. add nodes along the path. 4. then add edges along the path.

Image is binarised and thinned by using bwmorph command of matlab..

Answer 1

[Image Analyst]

I think you want bwmorph() with the 'endpoints' and 'branchpoints' options.

[Mohammad Bhat]

I extracted branch and end points with the bwmorph() functio itself. I just want to traverse the image after certain number of pixels replace the pixels with back ground...After that I will get sub-components of image...

[Image Analyst]

Why? You can subtract branchpoints from the original image to break it apart into segments. Then you'd have to write some custom code to "traverse" each segment but I see no reason to do this. Good luck on writing that code though.

[Mohammad Bhat]

here is algo which I want to implement:- 1. For each connected component 2. find junction points 3. invert junction points 4. For each connected sub-component 5. Find start and end points 6. add nodes along the path 7. replace neighbours of junction point 8. add edges based on skeleton. ----------------------------------------- image is filtered,binarised character image let us say small character 'e'...

Answer 2

[Walter Roberson]

https://www.mathworks.com/matlabcentral/fileexchange/34874-interparc

[Mohammad Bhat]

Unfortunately , it didn't help in my problem....

[Walter Roberson]

You asked that white pixels be placed at fixed distances along the path. That routine calculates where those positions are, given a path.

[Mohammad Bhat]

here is algo which I want to implement:-

1. 1. For each connected component
2. 2. find junction points
3. 3. invert junction points
4. 4. For each connected sub-component
5. 5. Find start and end points
6. 6. add nodes along the path
7. 7. replace neighbours of junction point
8. 8. add edges based on skeleton.

----------------------------------------- image is filtered,binarised character image let us say small character 'e'...

[Image Analyst]

None of that says to take every Nth pixel along some path.

[Mohammad Bhat]

Let us say , we have to add/replace two more nodes between two end points or between a branch point and end point or vice versa...remeber i have colored the branch and end points with white colour after extraction by bwmorph() command....

[Walter Roberson]

Okay, so for every two end points that you need to place nodes between, interparc can tell you where to put the nodes, if you want the nodes placed at equal distances traveled along the path.

If you want "every 5th pixel" then you need to define which is the 5th pixel when you have an arc

ABC
  DEFGH

if you start at A, is E or F or G the 5th pixel?

A->B->C->D->E   so maybe it is E
A->B->D->E->F   so maybe it is F
A->B->C->E->F   so maybe it is F
A->B->E->F->G   so maybe it is G

[Mohammad Bhat]

I have an filtered, binarised character image say letter 'e'...It is not necessary after every 5th pixel, but after regular intervals along the path...

[Mohammad Bhat]

How can I tailor interparc() function to my problem, let us say i have a line I have extracted end points of that line , Now I have to add nodes along the path of that line

[Image Analyst]

Why not simply use every pixel along the path? Why skip some?

[Mohammad Bhat]

Yes, that is what , we have to traverse every pixel and select some pixel or colour (make a node) based on some criteria.....

[Mohammad Bhat]

I have extracted branch and end points of a binary handwritten image of letter 'e' . Between every points (branch and end ) I have to place atleast two or three nodes more, inorder to represent it more accurately....

[Image Analyst]

You can remove the branchpoints to break apart the blobs. Then use regionprops() and ask for PixelIdxList to get the linear indexes or PixelList to get a list of (x,y) coordinates of pixels in the blob. This may not give pixels in the exact order - it probably does for linear shapes but you'd have to check for blobs that loop back, like a C shape.

Answer 3

[Mohammad Bhat]

If we have some code to begin with....If we try letter e...

[Mohammad Bhat]

John D'Errico's interparc , will it work for my case....