filter objects below a certain size in a binary image ?

clear
clc
A5=imread('C:\Users\AMIT\Desktop\CB\sulphur\4-5.jpg');
imshow(A5);
BW = im2bw(A5,0.5);
imshow(BW,0.5)

C = imcrop(BW);
bw2 = bwareaopen(C,5);
figure, imshow(bw2)
ComplementImage=imcomplement(bw2);
imshow(ComplementImage);
[labeledimage,numberofobject]=bwlabel(ComplementImage);
numberofobject
% bwareaopen is not working even if I increase 5 to another higher value

Answer 1

[Image Analyst]

Well of course not. You inverted the image so you have only one object - the background. Don't do that! 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 = 20;

originalImage=imread('D:\Temporary stuff/1234.jpg');
subplot(2,2,1);
imshow(originalImage);
axis on;
% 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') 

BW = im2bw(originalImage,0.5);
subplot(2,2,2);
imshow(BW, []);
axis on;

promptMessage = sprintf('Do you want to crop the image,\nor Cancel to abort processing?');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
  return;
end
message = sprintf('Drag out a box in the upper right image\nthen double-click inside to finish');
uiwait(helpdlg(message));
croppedImage = imcrop(BW);
bw2 = bwareaopen(croppedImage, 9);
bw2 = imclearborder(bw2); % Get rid of huge white surround.
subplot(2,2,3);
imshow(bw2)
axis on;
[labeledimage, numberofobjects] = bwlabel(bw2);
numberofobjects
message = sprintf('The number of objects = %d', numberofobjects);
uiwait(helpdlg(message));
measurements = regionprops(labeledimage, 'Area');
allAreas = sort([measurements.Area], 'Descend')

[AMIT VERMA]

thanks for helping me out but still it shows numberofobjects as 1 only and it'll be more than that, i'll attach a sample file here so that you could know what I am trying to count in that image, I have to reject only a few small black spots, rest all I will take the count of numberofobjects will be around 50-60 max not more than that

thanks in advance

[Image Analyst]

Well this is a totally different image! Your first image was a binary image and this one is a beige RGB image. Totally different. You need to binarize it first. What is your code for doing that?

[AMIT VERMA]

well the code I posted initially converts this image to a binary image , even in your program I was getting a binary image

[Image Analyst]

This one needs to be inverted since it's not a binary image to start with like the original image you posted. The code is below and does give different numbers of objects if you vary the parameter to bwareaopen().

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 = 20;

originalImage=imread('D:\Temporary stuff/4-1.jpg');
subplot(2,2,1);
imshow(originalImage);
axis on;
% 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')

BW = ~im2bw(originalImage,0.5);
subplot(2,2,2);
imshow(BW, []);
axis on;

promptMessage = sprintf('Do you want to crop the image,\nor Cancel to abort processing?');
titleBarCaption = 'Continue?';
button = questdlg(promptMessage, titleBarCaption, 'Continue', 'Cancel', 'Continue');
if strcmpi(button, 'Cancel')
  return;
end
message = sprintf('Drag out a box in the upper right image\nthen double-click inside to finish');
uiwait(helpdlg(message));
croppedImage = imcrop(BW);
bw2 = bwareaopen(croppedImage, 9);
bw2 = imclearborder(bw2); % Get rid of huge white surround.
subplot(2,2,3);
imshow(bw2)
axis on;
[labeledimage, numberofobjects] = bwlabel(bw2);
numberofobjects
message = sprintf('The number of objects = %d', numberofobjects);
uiwait(helpdlg(message));
measurements = regionprops(labeledimage, 'Area');
allAreas = sort([measurements.Area], 'Descend')

[AMIT VERMA]

It worked ,You're the best thanks a ton