How to normalize/Rescale Image Datastore

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hammad younas 2021-11-26

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评论： Image Analyst 2021-11-27

采纳的回答： Image Analyst

Hi, I want to Normilze/Rescale the Dataset between 0 and 1

In Keras the Following Function is used to Normalize the Data between 0 and 1

train_image_generator = ImageDataGenerator(
    rescale=1./255,)
    
 %% in MATLAB i am using ImageDatastore 
 imageFolder = fullfile(downloadFolder,'Classdata');
 imds = imageDatastore(imageFolder, 'LabelSource', 'foldernames', 'IncludeSubfolders',true);
 

How can i Normalize the ImageDatastore in MATLAB?

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Image Analyst 2021-11-26

Do you mean you just want to read in images one at a time and rescale them to a range of 0-1 with mat2gray() or rescale()?

hammad younas 2021-11-26

@Image Analyst mat2gray() convert image into grayscale. I want to rescale the whole imagedatastore between 0-1

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采纳的回答

Image Analyst 2021-11-26

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https://ww2.mathworks.cn/matlabcentral/answers/1596789-how-to-normalize-rescale-image-datastore#answer_841189

@hammad younas an imageDatastore is essentially just a structure that is a listing of file names. It is not image data itself. So you'd loop over the images and call rescale(thisImage, 0, 1) on each image, and then do something with it, like call image processing functions or something.

% Demo by Image Analyst
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;
markerSize = 40;
folder = pwd;
imds = imageDatastore(folder, "FileExtensions", [".jpg",".tif", ".png"])
numImages = length(imds.Files)
%numImages = 4; % For debugging.
plotRows = ceil(sqrt(numImages))
for k = 1 : numImages %length(imds.Files)
    thisFile = imds.Files{k}
    [f, baseFileName, ext] = fileparts(thisFile);
    % Read in the image.
    thisImage = imread(thisFile);
    % Scale the min to 0 and the max to 1.
    thisImage = rescale(thisImage, 0, 1);
    % Now do something with the rescaled image.
    subplot(plotRows, plotRows, k);
    imshow(thisImage);
    title(baseFileName, 'FontSize', fontSize);
    text(10, 10, baseFileName, 'Color', 'r', ...
        'BackgroundColor', 'y', 'FontSize', fontSize, 'VerticalAlignment', 'top')
end
g = gcf;
g.WindowState = 'maximized'

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hammad younas 2021-11-27

@Image Analyst In keras we normalize image using

img = cv2.resize(cv2.imread(path),(150,150)) 
img_normalized = img/255

How can i do this in above code?

Image Analyst 2021-11-27

% Read in the image.
thisImage = imread(thisFile);
% Resize to 150,150.
thisImage = imresize(thisImage, [150, 150]);
% Scale the max to 1, and everything else linearly scaled.
thisImage = thisImage / 255;
% Now do something with the resized and rescaled image.

Of course you could string that all together into one really long line of code (like your other code) if you want, though it might make it harder to read and follow.

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