I want to get chain code but it is showing error. Please help me.

I=imread('C:\Users\abcd\Desktop\mini.jpg');
bw=im2bw(I)
bw=~bw;
BW2 = bwperim(bw,8);
image=BW2;
[x y]=find(image==1);
b=[x y];
[cc]=chaincode(b)

This is showing eror: ??? Undefined function or method 'chaincode' for input arguments of type. Please tell me where I am making mistake. 'double'.

Answer 1

[Image Analyst]

Why do you think there is a function called chaincode()? I think you want bwboundaries() instead.

[MONIKA SAINI]

To separately encode each connected component (4 or 8 directional connected)or blob in a image chain code is used. I have seen a number of papers in which freeman chain code is extracted with the help of matlab software.

[Image Analyst]

What do you want to do? What is the big picture? I'm sure you don't want to just measure the chain code and then quit. Would you say to your supervisor or project sponsor, "Here you go, here's your chain code!"? No. What is your final deliverable? Can you attach an image? Once you have the chain code, what would you want to do next? What is the final measurement that needs to be made?

Anyway, you can get the chain code from the x,y coordinates pretty trivially.

[Image Analyst]

MONIKA's "Answer" moved here since it's not an answer to her original question.

I am a Ph.D. scholar and I am working in the field of handwriting recognition and pattern recognition. I read in a few articles that the average number of exterior and interior contours can be used as a measure of writing movement. Highly cursive handwriting, for example, would have a greater number of interior contours and fewer exterior contours, while script-like writing would have a very large number of exterior contours. These number of exterior and interior contour can be extracted from chain code presentation of the image. Please suggest to me if there is any other way to compute the writing movement. I've also used bwlabel function to find out differences in handwriting samples in terms of connected components.

If i want to find out the number of interior and exterior contour then what should I do? Please guide me. Attached is the jpg file of a word.

[Image Analyst]

Just threshold it do get a binary image, then use bwboundaries. Then put into a loop and build the chain code. Here's a start:

% Code to create a chain code from the boundaries of an binary image.
clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables. Or clearvars if you want.
workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fontSize = 25;

% Create sample image.
z=peaks(500);
subplot(1,2,1);
imshow(z, []);
axis on;
title('Original Grayscale Image', 'FontSize', fontSize);

% Threshold it to form a binary image.
binaryImage = z > 2;
subplot(1,2,2);
imshow(binaryImage);
axis on;
title('Binary Image', 'FontSize', fontSize);
subplot(1,2,1);
% Enlarge figure to full screen.
set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
% Give a name to the title bar.
set(gcf, 'Name', 'Demo by ImageAnalyst', 'NumberTitle', 'Off') 

% Find the outer perimeter of the two blobs.
boundaries = bwboundaries(binaryImage);
for k = 1 : length(boundaries)
  % Get the k'th boundary.
    thisBoundary = boundaries{k};
  % Get the x and y coordinates.
    x = thisBoundary(:, 2);
    y = thisBoundary(:, 1);
  % Plot this boundary over the original image.
  hold on;
  plot(x, y, 'r-', 'LineWidth', 2);
  % Create the chain code.
    for p = 2 : length(y)
    % See where the current point is relative to the prior point.
        if x(p) < x(p-1) && y(p) < y(p-1)
            % Moved to the upper left
            thisChainCode(p) = 1;
        elseif x(p) == x(p-1) && y(p) < y(p-1)
            % Moved straight up
            thisChainCode(p) = 2;
        elseif x(p) > x(p-1) && y(p) < y(p-1)
            % Moved to the upper right
            thisChainCode(p) = 3;
        elseif x(p) > x(p-1) && y(p) == y(p-1)
            % Moved right
            thisChainCode(p) = 4;
        elseif x(p) > x(p-1) && y(p) > y(p-1)
            % Moved right and down.
            thisChainCode(p) = 5;
        elseif x(p) == x(p-1) && y(p) > y(p-1)
            % Moved down
            thisChainCode(p) = 6;
        elseif x(p) <= x(p-1) && y(p) > y(p-1)
            % Moved down and left
            thisChainCode(p) = 7;
        elseif x(p) <= x(p-1) && y(p) == y(p-1)
            % Moved left
            thisChainCode(p) = 8;
        end
    end
    % Save the chain code that we built up for this boundary
  % into the cell array that will contain all chain codes.
    chainCodes{k} = thisChainCode
end
% Display the chain codes to the command window.
celldisp(chainCodes);

As you can see it's pretty easy. I just did that off the top of my head and is what you were probably thinking of but just didn't know how to code up. It may need a few tweaks and initializations though. If you can't finish it, let me know.

As you probably know since you're a Ph.D. in the image processing field, all or most of the handwriting published papers are listed here in Vision Bib: http://www.visionbib.com/bibliography/contentschar.html#OCR,%20Document%20Analysis%20and%20Character%20Recognition%20Systems in Section 23.4.6 and subsections.

[MONIKA SAINI]

Thanks for this help. Actually I am from Anthropology background. My topic of research is "handwriting variations among Indian populations" and I never had any kind of experience of programming. During my literature review stage I found out that most of the research in this field is done by computer scientist. I joined matlab classes to gain knowledge of image processing but didn't get much benefit. Can you help me in this matter?

[MONIKA SAINI]

How we can calculate interior and exterior contours from chain code?Please see the attached article.

[Image Analyst]

What do you mean by contours? Do you mean the x,y coordinates? Well that was what we started with from bwboundaries! There is no sense starting with the contours/boundaries/perimeters/outlines and then get chain codes, just to go back to where you started from. Just don't do the chain code then.

[MONIKA SAINI]

Can I have your Email id?I want to show you some articles. It would be easy for me to let you understand what I am looking for in my project.

[MONIKA SAINI]

Tell me bwboundaries(noholes) function gives the number of inner boundaries or outer boundaries??

[Image Analyst]

If you tell it to not find holes, it will find only the outer boundaries, not the boundaries of the holes.