How to save information from a for loop

%% DEFINE input and output path

full_folder = 'C:\Users\RR\Desktop\practice\input_folder_T_60_inj_05';
output_folder  = uigetdir("select folder");
input_files = fullfile(full_folder,"*.tif");
subfolders     = dir(input_files);

%% background subtraction
background = im2uint16(mat2gray(imread(subfolders(1).name))); 

%% Image processing
for i = 1 : length(subfolders)
    image = im2uint16(mat2gray(imread(subfolders(i).name)));
    image_back_sub = image - background;
    image_gray = im2gray(image_back_sub);
    tilt = imrotate(image_gray,-0.7,'bilinear','crop');
    %color_inversion = imcomplement(image_gray);  % this code works for color inversion
    BinaryImage=imbinarize(tilt, 0.1);
    bw1 = imopen(BinaryImage, strel('line', round(size(BinaryImage,2)*0.03), 0));
    bw2 = imdilate(bw1, strel('square', 4));
    bw3 = imdilate(bw2, strel('square', 2));
    
    stats = regionprops(bw3);
    data = struct2table(stats)
    [~,idx] = max(data.Area(:,1))
    r = data(idx,:)

    sprayRadius = r.BoundingBox(1,3)
    sprayHeight = r.BoundingBox(1,4)
    
    imwrite(bw3,[output_folder '/', subfolders(i).name]);
end

stats is the table shown above. I want to store last two values as sprayRadius and sprayHeight in every iteration. How can I do this? Thanks in advance. Reference images are in the comments (img1,img2,background)

[Image Analyst]

Why is there a loop? if bw2 does not change, then the regionprops won't change and so no loop is needed.

[Rohit Thokala]

Hello sir @Image Analyst, bw2 change everytime

[Rohit Thokala]

Hello sir (@Image Analyst), I want only width and height of the spray associated with maximum area in the table, not all the heights and widths. I am attaching my full code here with three images (one background and two spray images) for code to run. This code is working to process single image and I want to loop this over a range of images and finally get width and height of all images. I am also attaching single image processing code.

Answer 1

[yanqi liu]

result = [];
%% Image processing
for i = 1 : length(subfolders)
    image = im2uint16(mat2gray(imread(subfolders(i).name)));
    image_back_sub = image - background;
    image_gray = rgb2gray(image_back_sub);
    tilt = imrotate(image_gray,-0.7,'bilinear','crop'); % impingement plate has little inclination
    BinaryImage=imbinarize(tilt, 0.2);
    
    bw1 = imopen(BinaryImage, strel('line', round(size(BinaryImage,2)*0.03), 0));
    bw2 = imdilate(bw1, strel('square', 4));
    bw3 = imdilate(bw2, strel('square', 2));
    
    stats = regionprops(bw3);
    data = struct2table(stats)
    [~,idx] = max(data.Area(:,1))
    r = data(idx,:)
    figure; imshow(image, []); hold on;
    for j = 1 : length(stats)
        rectangle('Position', stats(j).BoundingBox, 'EdgeColor', 'r', 'LineWidth', 2);
    end
    % loop this over a range of images and finally get width and height of all images
    sprayRadius = r.BoundingBox(1,3);
    sprayHeight = r.BoundingBox(1,4);
    %     sn(i).filename = subfolders(i).name;
    %     sn(i).sprayRadius = sprayRadius;
    %     sn(i).sprayHeight = sprayHeight;
    result{i,1} = subfolders(i).name;
    result{i,2} = sprayRadius;
    result{i,3} = sprayHeight;
    imwrite(BinaryImage,[output_folder '/', subfolders(i).name]);
end
xlswrite('result.xlsx',result)

[Rohit Thokala]

Hello @yanqi liu, I am getting the following error message.

[yanqi liu]

now b is empty，may be add if judge，such as

if isempty(data)

continue;

end

[Rohit Thokala]

Hello @yanqi liu, where can I add this to loop? sorry, I am new to coding

[yanqi liu]

yes，sir，please upload your new m file，and we can debug it

now，use last files，we can not find this error

[Rohit Thokala]

Hello @yanqi liu, it's just printing last value. I am adding code and associated pictures for reference in jpg format (since I can't upload TIF images to matlab community)

[Rohit Thokala]

Hello @yanqi liu, code is working properly. Thank you so much for your help

[yanqi liu]

clear all;
clc;
close all
%% DEFINE input and output path

full_folder = './input_folder_T_80_inj_10/';
output_folder  = './out';
input_files = fullfile(full_folder,"*.jpg");
subfolders     = dir(input_files);
result = [];
%% background subtraction
background = im2uint16(mat2gray(imread(fullfile(subfolders(1).folder,subfolders(1).name))));

%% Image processing
for i = 1 : length(subfolders)
    image = im2uint16(mat2gray(imread(fullfile(subfolders(1).folder,subfolders(i).name))));
    image_back_sub = image - background;
    image_gray = rgb2gray(image_back_sub);
    tilt = imrotate(image_gray,-0.7,'bilinear','crop');
    %color_inversion = imcomplement(image_gray);  % this code works for color inversion
    BinaryImage=imbinarize(tilt, 0.1);
    B2 = bwareafilt(BinaryImage, 1);           % select the largest component with bwareafilt
    % imshowpair(B,B2,"montage")
    bw1 = imopen(B2, strel('line', round(size(BinaryImage,2)*0.07), 0));
    bw2 = imdilate(bw1, strel('square', 2));
    
    widthIndex = any(B2);
    
    horizontalPixelWidth = find(widthIndex,1,'last')-find(widthIndex,1,'first');
    
    verticalPixelHeight = find(any(B2,2),1,'last') - find(any(bw2,2),1,'first');
    
    imwrite(bw2,[output_folder '/', subfolders(i).name]);
    result{i,1} = subfolders(i).name;
    result{i,2} = horizontalPixelWidth;
    result{i,3} = verticalPixelHeight;
end
result
xlswrite('result.xlsx',result)

Answer 2

[Image Analyst]

What is b? It shows b in the error but I don't see it in your code. You might have to attach your entire m-file.

Maybe try

bb = vertcat(stats.BoundingBox);
allWidths = bb(:, 3);
allHeights = bb(:, 4);
sprayRadius(i) = max(allWidths);
sprayHeights(i) = max(allHeights);