diving all images in folder into n horizental and vertical strips

i have 500 images and i want to divide all of them into 4 equal parts automatically and get stored to a new location. i have a code which can devide a image into n number of horizental and vertical strips but i want to use that code on all the images and store the cropped new 4 images to a seperate folder

Answer 1

[Image Analyst]

You can get the rows and columns like this

[rows, columns, numberOfColorChannels] = size(yourImage);
r = ceil(rows/4);
c = ceil(c/4);
dividingRows = 1 : r : rows;
dividingColumns = 1 : c : columns
for k = 1 : length(dividingRows)
    row1 = dividingRows(k);
    row2 = row1 + r;
    if row2 >= rows
        row2 = rows
    end
    thisBand = yourImage(row1:row2, :, :);
    % etc.
end
% Similar for columns.
for k = 1 : length(dividingColumns)
    col1 = dividingColumns(k);
    col2 = col1 + c;
    if col2 >= columns
        col2 = columns
    end
    thisBand = yourImage(:, col1:col2, :);
end

[Mujtaba Tahir]

But how can i apply it to all the images in the folder, and output the segmented photos to a separate folder, surely I can't do one by one for all images, also images are randomly named

[Image Analyst]

See the FAQ for code samples:

https://matlab.fandom.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

% Specify the folder where the input files live.
inputFolder = 'C:\Users\yourUserName\Documents\My Pictures';
% Check to make sure that folder actually exists.  Warn user if it doesn't.
if ~isfolder(inputFolder)
	errorMessage = sprintf('Error: The following folder does not exist:\n%s\nPlease specify a new folder.', inputFolder);
	uiwait(warndlg(errorMessage));
	inputFolder = uigetdir(); % Ask for a new one.
	if inputFolder == 0
		% User clicked Cancel
		return;
	end
end
% Specify the folder where the output files should be written to.
outputFolder = 'C:\Users\yourUserName\Documents\My Pictures\output';
% Check to make sure that folder actually exists.  Warn user if it doesn't.
if ~isfolder(outputFolder)
	mkdir(outputFolder);
end
% Get a list of all input PNG image files in the input folder with the desired file name pattern.
filePattern = fullfile(inputFolder, '*.png'); % Change to whatever pattern you need.
theFiles = dir(filePattern);
for k = 1 : length(theFiles)
	baseInputFileName = theFiles(k).name;
	fullInputFileName = fullfile(theFiles(k).folder, baseInputFileName);
	fprintf('Now reading "%s"\n', fullInputFileName);
	% Now do whatever you want with this file name,
	% such as reading it in as an image array with imread()
	imageArray = imread(fullInputFileName);
	imshow(imageArray);  % Display image.
	drawnow; % Force display to update immediately.
	
	% Now process the image somehow to create outputImage.
	% Now write output image to the output folder.
	baseOutputFileName = baseInputFileName;
	fullOutputFileName = fullfile(outputFolder, baseOutputFileName);
	fprintf('Now writing "%s"\n', fullOutputFileName);
	imwrite(outputImage, fullOutputFileName);
end

[Mujtaba Tahir]

i get the following error

[Mujtaba Tahir]

% Specify the folder where the input files live.

inputFolder = 'C:\Users\user\Pictures\Saved Pictures';

% Check to make sure that folder actually exists. Warn user if it doesn't.

if ~isfolder(inputFolder)

errorMessage = sprintf('Error: The following folder does not exist:\n%s\nPlease specify a new folder.', inputFolder);

uiwait(warndlg(errorMessage));

inputFolder = uigetdir(); % Ask for a new one.

if inputFolder == 0

% User clicked Cancel

return;

end

end

% Specify the folder where the output files should be written to.

outputFolder = 'C:\Users\user\Pictures\Saved Pictures\New folder';

% Check to make sure that folder actually exists. Warn user if it doesn't.

if ~isfolder(outputFolder)

mkdir(outputFolder);

end

% Get a list of all input PNG image files in the input folder with the desired file name pattern.

filePattern = fullfile(inputFolder, '*.png'); % Change to whatever pattern you need.

theFiles = dir(filePattern);

for k = 1 : length(theFiles)

baseInputFileName = theFiles(k).name;

fullInputFileName = fullfile(theFiles(k).folder, baseInputFileName);

fprintf('Now reading "%s"\n', fullInputFileName);

% Now do whatever you want with this file name,

% such as reading it in as an image array with imread()

imageArray = imread(fullInputFileName);

imshow(imageArray); % Display image.

drawnow; % Force display to update immediately.

% Now process the image somehow to create outputImage.

[rows, columns, numberOfColorChannels] = size(imageArray);

r = ceil(rows/4);

c = ceil(columns/4);

dividingRows = 1 : r : rows;

dividingColumns = 1 : c : columns;

for k = 1 : length(dividingRows)

row1 = dividingRows(k);

row2 = row1 + r;

if row2 >= rows

row2 = rows;

end

thisBand = imageArray(row1:row2, :, :);

% etc.

end

% Similar for columns.

for k = 1 : length(dividingColumns)

col1 = dividingColumns(k);

col2 = col1 + c;

if col2 >= columns

col2 = columns;

end

thisBand = imageArray(:, col1:col2, :);

end

% Now write output image to the output folder.

baseOutputFileName = baseInputFileName;

fullOutputFileName = fullfile(outputFolder, baseOutputFileName);

fprintf('Now writing "%s"\n', fullOutputFileName);

imwrite(outputImage,fullOutputFileName);

end

this is code i am using and getting this error

Now reading "C:\Users\user\Pictures\Saved Pictures\Screenshot (1).png"

Now writing "C:\Users\user\Pictures\Saved Pictures\New folder\Screenshot (1).png"

Unrecognized function or variable 'outputImage'.

Error in div_4_1 (line 60)

imwrite(outputImage,fullOutputFileName);

[Mujtaba Tahir]

@Image Analyst the last issue i am facing is that my programme is saving only the last segmented image how can i fix it please

% Specify the folder where the input files live.
inputFolder = 'C:\Users\user\Pictures\Saved Pictures';
% Check to make sure that folder actually exists.  Warn user if it doesn't.
if ~isfolder(inputFolder)
	errorMessage = sprintf('Error: The following folder does not exist:\n%s\nPlease specify a new folder.', inputFolder);
	uiwait(warndlg(errorMessage));
	inputFolder = uigetdir(); % Ask for a new one.
	if inputFolder == 0
		% User clicked Cancel
		return;
	end
end
% Specify the folder where the output files should be written to.
outputFolder = 'C:\Users\user\Pictures\Saved Pictures\New folder';
% Check to make sure that folder actually exists.  Warn user if it doesn't.
if ~isfolder(outputFolder)
	mkdir(outputFolder);
end
% Get a list of all input PNG image files in the input folder with the desired file name pattern.
filePattern = fullfile(inputFolder, '*.png'); % Change to whatever pattern you need.
theFiles = dir(filePattern);
for k = 1 : length(theFiles)
	baseInputFileName = theFiles(k).name;
	fullInputFileName = fullfile(theFiles(k).folder, baseInputFileName);
	fprintf('Now reading "%s"\n', fullInputFileName);
	% Now do whatever you want with this file name,
	% such as reading it in as an image array with imread()
	imageArray = imread(fullInputFileName);
	imshow(imageArray);  % Display image.
	drawnow; % Force display to update immediately.

	
	% Now process the image somehow to create outputImage.

workspace;  % Make sure the workspace panel is showing.
format long g;
format compact;
fprintf('Beginning to run %s.m ...\n', mfilename);

% Read in image
grayImage = imread(fullInputFileName);
[rows, columns, numColorChannels] = size(grayImage);
imshow(grayImage);
axis on;
impixelinfo

numBandsVertically = 2;
numBandsHorizontally = 2;
topRows = round(linspace(1, rows+1, numBandsVertically + 1));
leftColumns = round(linspace(1, columns+1, numBandsHorizontally + 1));
% Draw lines over image
for k = 1 : length(topRows)
	yline(topRows(k), 'Color', 'y', 'LineWidth', 2);
end
for k = 1 : length(leftColumns)
	xline(leftColumns(k), 'Color', 'y', 'LineWidth', 2);
end

% Extract into subimages and display on a new figure.
hFig2 = figure();
plotCounter = 1;
for row = 1 : length(topRows) - 1
	row1 = topRows(row);
	row2 = topRows(row + 1) - 1;
	for col = 1 : length(leftColumns) - 1
		col1 = leftColumns(col);
		col2 = leftColumns(col + 1) - 1;
		subplot(numBandsVertically, numBandsHorizontally, plotCounter);
		subImage = grayImage(row1 : row2, col1 : col2, :);
		imshow(subImage);
		caption = sprintf('Rows %d-%d, Columns %d-%d', row1, row2, col1, col2);
		title(caption);
		drawnow;
		plotCounter = plotCounter + 1;
        % Now write output image to the output folder.
	baseOutputFileName = baseInputFileName;
	fullOutputFileName = fullfile(outputFolder, baseOutputFileName);
	fprintf('Now writing "%s"\n', fullOutputFileName);
	imwrite(subImage, fullOutputFileName);
	end
end

end

[Image Analyst]

You're not changing the name at all. You're just using the same name for all images you save. To fix it try this:

[~, baseNameNoExt, ext] = fileparts(baseInputFileName);
baseOutputFileName = sprintf('%s, row %2.2d, col %2.2d.png', baseNameNoExt, row, col);