curve fitting, basic fitting for irregular ,specific geometric shapes?

i have a region. i want to detect this object with basic or curve fitting.

for example, i want to pass all the pixels on coordinate plane and do a fitting.

http://uploadpic.org/v.php?img=K3AAlYW0M8 from Image to coordinate plane it becomes http://uploadpic.org/v.php?img=UGXFCNWzaQ

i tried basic fitting but i failed. i was expecting something like that :

http://uploadpic.org/v.php?img=n2uYT6wQUL

(i made up)

because it happens correctly as seen in this application : http://uploadpic.org/v.php?img=NbFaNr7if5

Answer 1

[Image Analyst]

Did you try polyfit() and polyval()? What was your code? What was the error message? I did it and it seemed to work perfectly well:

clc;    % Clear the command window.
close all;  % Close all figures (except those of imtool.)
clear;  % Erase all existing variables.
workspace;  % Make sure the workspace panel is showing.
fontSize = 16;

% Read in selim's demo image.
folder = 'C:\Users\selim\Documents';
baseFileName = 'C54DlekrK51DuexHIM4AXxiL.jpg';
% Get the full filename, with path prepended.
fullFileName = fullfile(folder, baseFileName);
% Check if file exists.
if ~exist(fullFileName, 'file')
  % File doesn't exist -- didn't find it there.  Check the search path for it.
  fullFileName = baseFileName; % No path this time.
  if ~exist(fullFileName, 'file')
    % Still didn't find it.  Alert user.
    errorMessage = sprintf('Error: %s does not exist in the search path folders.', fullFileName);
    uiwait(warndlg(errorMessage));
    return;
  end
end
rgbImage = imread(fullFileName);
subplot(2, 1, 1);
imshow(rgbImage, []);
axis on;
title('Original Color Image (already cropped)', 'FontSize', fontSize);
set(gcf, 'Position', get(0,'Screensize')); % Maximize figure.

% Get the magenta points.  Subsample by a factor of 4.
redChannel = rgbImage(1:4:end,1:4:end, 1) > 128;
[rows columns] = size(redChannel);
subplot(2, 1, 2);
imshow(redChannel, []);
axis on;
title('Red Channel', 'FontSize', fontSize);

%-------------------------------------
% Main code starts here !!!!!
% Get all the x,y points
[y x] = find(redChannel);

% Plug into polyfit
orderOfPolynomial = 2;
coeffs = polyfit(x, y, orderOfPolynomial)

% Get the estimated fit and plot over the image.
xValues = 1 : columns;
fittedY = polyval(coeffs, xValues);
hold on;
plot(xValues, fittedY, 'b-', 'LineWidth', 3);
title('Red Channel with Fitted Curve', 'FontSize', fontSize);

[selim]

close all 
imtool close all
load v1 % v1 is my image that has been saved in matrix including '0' and '1'
figure(1)
subplot(2,1,1)
imshow(v1)
v1=imrotate(v1,270)
a=size(v1)
for i=1:a(1)
  for j=1:a(2)
           if v1(i,j)==1
       subplot(2,1,2)
               plot(i,j,'*')
      hold all
    end
  end
end

this is the result: http://uploadpic.org/v.php?img=tsCcvcoh15

[Image Analyst]

Hmmm.... Looks like all you did was rotate it and not do any fitting to a curve whatsoever. So no wonder no fitting occurred. Are you going to try my code?

[selim]

Sir, i tried figure->tools->basic fitting then i clicked quadratic and then it really lags my netbook.

[Image Analyst]

So I guess the answer is no. If not, then tell me why I should put more effort into helping you some more considering what happened with my last attempt.

[selim]

thank you sir for everything . but i think i made my problem more complex considering that i can solve this using basic fitting. i should not have thought that i must solve it by basic fitting.