Freeman Chain Code

Gives Freeman chain code 8-connected representation of a boundary

Description

usage:
--------------------------------------------------------
    [cc] = chaincode(b,u)

  INPUT:
--------------------------------------------------------
    b - boundary as np-by-2 array
    unwrap - (optional, default=false) unwrap code

  OUTPUT:
 --------------------------------------------------------
    cc is a structure with the following fields:
    cc.code - 8-connected Freeman chain code 1-by-np
    cc.x0,cc.y0 - coordinates of start point
    cc.ucode - unwrapped 8-connected Freeman chain code

• MATLAB release: MATLAB 7.8 (R2009a)

[Daurat Sinaga]

i was running this function and i get output like this :
CC =
x0:0
y0:0
code:[209x1 double], would you explain it for me ?

[rana]

would you tell me please the exact steps to run this code ??
than you :)

[Alessandro Mannini]

Hi Ann, look to my previous comments (ex. 19/3/2011) the b parameter is an array containing coords of boundary points that should be 8-connected. 8-connected means that if Bn is the n-th element of b and Bn+1 the next their x y coords should satisfy this relations: | Xn - Xn+1 |<=1 AND | Yn - Yn+1 |<=1. Start checking that with a simple example. Regards Alessandro

[Ann]

i am trying to use this code on the image but i am getting the error "Curve isn't 8-connected in elements: "

what to do?

[Alessandro Mannini]

Hi Frb, please note than b contains coords of boundary points order so that they are 8-connected. The find function you use return coords of boundary points but in a different order. From Matlab Help seems it scans matrix column by column. Best regards Alessandro

[Frb]

hello,
I checked this code, seems very useful but I have problem, I give this piece of code to make it 8-connected:
I=imread('im1.jpg');
BW1=im2bw(I);
BW1=~BW1;
BW2 = bwperim(BW1,8);
image=BW2;
[x y]=find(image==1);
b=[x y];
and then I put the result in b,
when I run the code error applies and says Curve isn''t 8-connected in elements. I appreciate any help.

Kind Regards,
Fariba

[Anush]

if i have an image what's the procedure to find the chain code for that particular image !

[hamza]

Thanks for your great work, and I have a question :-
I have image called XYZ.png and I passed that images to this function but I found an error.

Please help me in how to execute this function.

[maddy]

i had a skeleton with me which i want to give as a input to this chaincode..and when i tried to do that...i am getting that subscript indices are must be either positive or real...please somebody help me in resolving this...

[Amr]

i have a silhouette for human image(http://i.imgur.com/fTwkZ.png) and I put the image boundary in an array and then i passed it to the Freeman Chain Code function. this image shows the body boundary is connected to each other but in real it gives me this error
"Curve isn't 8-connected in elements:
idx -> 350
idx -> 700
idx -> 1050
idx -> 1400
....
"

so can any one help me please? :)

[Alessandro Mannini]

Look at description inside source code:

% b - boundary as np-by-2 array;
% np is the number of pixels and each element is a pair (y,x) of
% pixel coordinates

For example, if you have 4 points p=(y,x) like this p1=(5,1);p2=(5,2);p3=(4,2);p4=(3,1) b is:

b = [ 5 1;5 2;4 2;3 1]

note that points must be 8-connected.

[Manhal]

hi,
what should be the input for "b"?
is it an image or what ??
need help as soon as possible pls ..
thanx

[Santhosh R]

A very nice self explanatory code!!
Was very useful for my project.
Great job!!!!!!!!!