How can I automatically do thresholding multiple images in a folder by for loop?

Hello everyone. I have 100 images in a folder. I intend to read all the images and threshold it in order to count the black pixels in my image. The problem is that I can only do it for one image and not for all of them. Below is the code that I used for only one image. Any help would be appreciated.

clear all;close all;clc;

      A=imread('1.png');
      [X,map]=imread('1.png');
      A=imresize(A,1);
      figure
      imshow(A)
      figure
      A=rgb2gray(A);
      A=medfilt2(A,[1,1]);
      level = graythresh(A);
      BW = im2bw(X,map,0.45);
      imshow(BW)

      blackpixels_eachtime=sum(BW(:)==0)
      Total_black_pixels=648282;
      RF=((Total_black_pixels-blackpixels_eachtime)/(Total_black_pixels))*100

Answer 1

[Image Analyst]

Check the FAQ: How do I process a sequence of files?

[Parham Babakhani]

Thank you very much for your response. I checked the link and I tried to read, made gray and binarized images. However, I could not still extract the black pixel for each image (I have 100 images, so I must have 100 numbers of total black pixels. Below is the code. It only gives me one value.

clc; clear all;close all;

images=dir('*.png');

N=length(images);
I=imread(images(1).name);

for i=1:numel(images)
    I=images(i).name;
    rgbImg=imread(I);

      gsImg=rgb2gray(rgbImg);
      gsImg=im2bw(gsImg, 0.54);

      [~,name,~]=fileparts(I);
      gsFilename=sprintf('%s_gs.png', name);
      imwrite(gsImg, gsFilename);

          for k=1:length(gsImg)

              blackpixels_t=sum(gsImg(:)==0)

          end

end

[Image Analyst]

You should not have that inner loop. I made a lot of other fixes, and here is the repaired code:

clc;    % Clear the command window.
fprintf('Beginning to run %s.m.\n', mfilename);
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 = 15;

imageList = dir('*.png');
numberOfImages = length(imageList);
for k = 1 : numberOfImages
	fullfileName= fullfile(imageList(k).folder, imageList(k).name);
	rgbImage = imread(fullfileName);
	% Optional display of the image.
	imshow(rgbImage);
	title(imageList(k).name, 'FontSize', fontSize, 'Interpreter', 'none');
	drawnow;
	[rows, columns, numberOfColorChannels] = size(rgbImage);
	if numberOfColorChannels == 3
		% Convert to gray scale.
		grayScaleImg = rgb2gray(rgbImage);
	else
		% It's already gray scale.
		grayScaleImg = rgbImage;
	end
	grayScaleImg = im2bw(grayScaleImg, 0.54);
	
	[~,baseFileNameNoExt,~] = fileparts(fullfileName);
	gsFilename=sprintf('%s_gs.png', baseFileNameNoExt);
% 	imwrite(grayScaleImg, gsFilename);
	blackPixels(k) = sum(grayScaleImg(:)==0);
end
bar(blackPixels, 1);
caption = sprintf('Number of black pixels for %d images', numberOfImages);
title(caption, 'FontSize', fontSize, 'Interpreter', 'none');
xlabel('Image Number', 'FontSize', fontSize);
ylabel('Number of Black Pixels', 'FontSize', fontSize);
grid on;
g = gcf;
g.WindowState = 'maximized'
fprintf('Done running %s.m.\n', mfilename);

[Parham Babakhani]

Well done. It could not work better than this.