how to remove some regions from the image

good day all, my objective is to extract optic disc from the image..when i try to extract it i get some unwanted regions..is it possible or is there any method to remove unwaneted regions from the image . in the image below i want all white regions to be eliminated...inside white region there is a black color round shaped region, that is my optic disc and i want only that black part to remain

Answer 1

[Image Analyst]

Try this code:

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 = 18;

% Read in a standard MATLAB gray scale demo image.
folder = 'D:\Temporary stuff';
baseFileName = 'optic.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.
  fullFileNameOnSearchPath = baseFileName; % No path this time.
  if ~exist(fullFileNameOnSearchPath, '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
grayImage = imread(fullFileName);
% Get the dimensions of the image.  
% numberOfColorBands should be = 1.
[rows, columns, numberOfColorBands] = size(grayImage);
if numberOfColorBands > 1
  % It's not really gray scale like we expected - it's color.
  % Convert it to gray scale by taking only the green channel.
  grayImage = grayImage(:, :, 2); % Take green channel.
end
% Display the original gray scale image.
subplot(2, 2, 1);
imshow(grayImage, []);
axis on;
title('Original Grayscale Image', 'FontSize', fontSize);
% 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') 

% Binarize, invert, and clear border.
binaryImage = (grayImage < 128);
binaryImage = imclearborder(binaryImage);
subplot(2, 2, 2);
imshow(binaryImage, []);
title('Initial Binary Image', 'FontSize', fontSize);
axis on;

% Measure sizes
labeledImage = bwlabel(binaryImage);
measurements = regionprops(labeledImage, 'Area');
allAreas = [measurements.Area];
[biggestArea, indexOfBiggest] = sort(allAreas, 'descend')
% Extract largest
biggestBlob = ismember(labeledImage, indexOfBiggest(1));
% Convert to binary
biggestBlob = biggestBlob > 0;
subplot(2, 2, 3);
imshow(biggestBlob, []);
title('Final Binary Image', 'FontSize', fontSize);
axis on;

[vidya]

sir ..it works fine only for this particular image ..rest of the image it does not remove the unwanted region ..i think its probably cause of threshold problem...ny other way

[Image Analyst]

Everything I do is based on just the one image you supply. And if different images look different you may need a more robust algorithm. That's why I keep telling you to not waste time with some simplistic algorithm of your own, that may need an image-by-image tweaking, and see the more robust algorithms that were published here: http://iris.usc.edu/Vision-Notes/bibliography/contentsmedical.html#Medical%20Applications,%20CAT,%20MRI,%20Ultrasound,%20Heart%20Models,%20Brain%20Models in section 20.5.

Answer 2

[Meshooo]

You can solve it by labeling. Try this code:

I = imread('optic.jpg');
%
bw = im2bw(I); % make it binary
bw = ~bw;
imshow(bw)
L = bwlabel(bw);

% Show the object labeled first.
imshow(L == 23)  % your targeted object was number 23

Hope that solves your problem..

Answer 3

[Dishant Arora]

Why not mask out region of interest using imfreehand.

h = imfreehand(gca);
wait(h)  % waits for user to specify region of interest 
bw = createMask(h)  % Binary mask with 1's inside ROI