How to save output images after preprocessing into new folder sequentially without overwriting?

I am have to convert RGB images into gray scale, as there are hundreds of images in that folder. I want to processess all and save the resultant gray scale images into different folder. Can I get code for this?

Answer 1

[KSSV]

infolder = ''   % give the path of the folder where your RGB images are present 
outfolder = ''   % give the path of the folder where you want to save gray images 
imgFiles = dir([infolder,filesep,'\*.png']) ;  % give extension of your images 
N = length(imgFiles) ;   % total images in the foder 
for i = 1:N
    thisFile = [infolder,filesep,imgFiles(i).name] ;   % each image file 
    [filepath,name,ext] = fileparts(thisFile) ;  % get name of the image file and extension 
    outFile = [outfolder,filesep,[name,ext]] ;   % write gray image file on this name here 
    I = rgb2gray(imread(thisFile)) ;   % reac and conver RGB image into gray 
    imwrite(I,outFile) ;   % write the gray image in the said folder on the name 
end

[Nikhat Ali]

Thank you so much, it worked. But some of the image in my input folder are in jpeg format, I want to process them and also want to change the extensioin of output image to png only. Where else do I need to make changes in the given code?

infolder = ''   % give the path of the folder where your RGB images are present 
outfolder = ''   % give the path of the folder where you want to save gray images 
imgFiles = dir([infolder,filesep,'\*.jpg']) ;  % give extension of your images 
N = length(imgFiles) ;   % total images in the foder 
for i = 1:N
    thisFile = [infolder,filesep,imgFiles(i).name] ;   % each image file 
    [filepath,name,ext] = fileparts(thisFile) ;  % get name of the image file and extension 
    outFile = [outfolder,filesep,[name,ext]] ;   % write gray image file on this name here 
    I = rgb2gray(imread(thisFile)) ;   % reac and conver RGB image into gray 
    imwrite(I,outFile) ;   % write the gray image in the said folder on the name 
end

[KSSV]

Change this :

imgFiles = dir([infolder,filesep,'\*.jpg']) ; 

to

imgFiles = dir([infolder,filesep]) ; 

And change this

outFile = [outfolder,filesep,[name,ext]] ;  

to

outFile = [outfolder,filesep,[name,'.png']] ;  

[Nikhat Ali]

Thank you

[Nikhat Ali]

I am getting some error, folder consist of 100 images.I have attached the error image

[KSSV]

Yes, you should run the loop from 3.

for i = 3:N
end

Try to analyse why you are getting error. The erro message is clear. For i = 1,2 , the file names will be '.', '..' .

[Nikhat Ali]

It worked, Thank you

[Stephen23]

Assuming that the first two filenames are '.' and '..' is buggy, anti-pattern, and not recommended.

@Nikhat Ali: Do NOT follow any poor advice advising to remove the first two filenames. Your original approach of specifying the file-extension is a much more robust approach. Or you could remove any folders using the ISDIR field:

S = dir(..);
S([S.isdir]) = [];

https://www.mathworks.com/matlabcentral/answers/345841-unexplained-error-on-dir#answer_271627

https://www.mathworks.com/matlabcentral/answers/21150-function-call#comment_46042

https://www.mathworks.com/matlabcentral/answers/394807-create-text-file-containing-list-of-file-names#comment_556641

https://www.mathworks.com/matlabcentral/answers/288815-gui-for-loop-not-working-correctly#answer_224956

https://www.mathworks.com/matlabcentral/answers/484430-using-struct-dir-selpath-what-do-and-mean-as-struct-name#answer_395754

https://www.mathworks.com/matlabcentral/answers/40949-omitting-pointers-when-listing-folder-contents#answer_50568

https://www.mathworks.com/matlabcentral/answers/13978-list-of-files-sorting#answer_19278

As Walter Roberson wrote in that last link: "In short: if your code assumes that '.' and '..' are the first two entries in a directory, your code has a bug (even in MS Windows). If your code assumes that directory entries are returned in any sorted order, your code has a bug (in all OS.)"

Unfortunately poor advice keeps getting repeated and copied by beginners.