What to do in matlab when working with images

So guys, i am working on images 3D rekonstruction with photometric stereo methode, which involve takin certain 2D images and process into 3D image. So my question is, after u take 6 pictures of surface that have 3840 x 2160 , what process should i do to make it smaller?. When i see photometric stereo example their dataset only have 512 x 34, how to achive this? what kind of process should i do? Pls guide me

[pizzaa]

i mean each picture in their dataset has 512 x 340

Answer 1

[Mathieu NOE]

hello

first code example :

%%  Initalize the data 
dataDir= fullfile(pwd); % select appropriate directory
exts = {'.jpg','.png','.tif'}; % choose valid file extensions like {'.jpg', '.png'}
 
resize_size = 100;      % pixels size for output img 
 
imds = imageDatastore(fullfile(dataDir),...
'IncludeSubfolders',true,'FileExtensions',exts,'LabelSource','foldernames');
countEachLabel(imds);
 
numImages = numel(imds.Files); 
for i = 1:numImages
    img = readimage(imds, i);
    [m,n,p] = size(img);
    % compute scale factor (same on both  dimensions)
    scale_factor = min(resize_size/m,resize_size/n);
    img3= imresize(img, scale_factor);
    figure(i),
    img4= imshow(img3, 'InitialMagnification', 800);
     drawnow;
    Train{i} = (img3);         %output image stored in cell
end

second example

% select appropriate options below and adapt code to your specific needs ...

% files = dir('*.tif');      % select all tiff files in current directory
files = dir('handheld*.tif');      % select only tiff files with "handheld" in the filename

% resize options (sacle factor or pixels)
scale_factor = 0.5;

% select portion of the image
% 451*279*3. I will like to extract a portion with dimensions of 120*80*3
x_dim = 120;
y_dim = 80;
x_offset = 100; % please make sure the "corner" of the cropped image is correct
y_offset = 50;

% output directory 
out_dir = fullfile(pwd,'\out'); % from current directory to sub directory \out

% main loop
for ck = 1:length(files)
    Filename = files(ck).name;
    img = imread(Filename);
    
    % resize
    H{ck}= imresize(img, scale_factor);

    % select (crop)
    H{ck}= img(x_offset+(1:x_dim),y_offset+(1:y_dim),: );

    % plot (just to check)
    figure(ck), imagesc(H{ck});
    
    % insert your own code here (save for example)
    filename = ['out' num2str(ck) '.tiff'];
    imwrite(H{ck},fullfile(out_dir,filename));
    
end