Recursively compressing images in a folder-structure, preserving the folder-structure

Question

I have this folder-strucutre, with really heavy high-quality images in each subfolder

tree -d ./

Output:

./
├── 1_2dia-pedro
├── 3dia-pedro
│   ├── 101MSDCF
│   └── 102MSDCF
├── 4dia-pedro
└── Wagner
    ├── 410_0601
    ├── 411_0701
    ├── 412_0801
    ├── 413_2101
    ├── 414_2801
    ├── 415_0802
    ├── 416_0902
    ├── 417_1502
    ├── 418_1602
    ├── 419_1702
    ├── 420_2502
    └── 421_0103

18 directories

And, I want to compress it, just like I would do with ffmpeg, or imagemagick. e.g.,

ffmpeg -i %%F -q:v 10 processed/%%F"
mogrify -quality 3 $F.png

I'm currently think of creating a vector of the directories, using shopt, as discussed here

shopt -s globstar dotglob nullglob
printf '%q\n' **/*/

Then, create a new folder-compressed, with the same structure

mkdir folder-compressed
<<iterate the array-vector-out-of-shopt>>

Finally, compress, for each subfolder, something in the lines of

mkdir processed
for f in *.jpg;
    do ffmpeg -i "$f" -q:v 1 processed/"${f%.jpg}.jpg"; 
done

Also, I read this question, and this procedure seems close to what I would like,

for f in mydir/**/*
do
  # operations here
done

Major problem: I'm bash newbie. I know all tools needed are at my disposal!

EDIT: There is a program that, for the particular purpose of compressing images with lossless quality, gives us a a-liner, and a lot of options to this compression. The caveat: make another copy of the original folder-structure-files, because it will change them permanently in the folder-structure-files you give it.

cp -r ./<folder-structure-files> ./<folder-structure-files-copy>
image_optim -r ./<folder-structure-files-copy>

I think @m0hithreddy solution is pretty cool, though. Certainly, I will be using that logic elsewhere anytime soon.

You're mixing bash and batch syntax here. Which language do you want to do this in? And, if your directory looks like that, you don't need recursion. — oguz ismail, May 23 '21 at 12:48
It's in bash, uniquely. I edited the post, to make that explicit. Thanks. About the need for recursion: I will run the script on the top level of a folder, which has 5 other subfolders, which some of them have subsubfolders. So, I think recursion is a perfect fit - I want the behavior similar to $(cp -r). Of course, in this case I'm applying a compression, not only copying the files — BuddhiLW, May 23 '21 at 13:39

m0hithreddy · Accepted Answer · 2021-05-27T04:47:05.807

Instead of pre-mkdiring directories, you can create the required directories on the fly. Recursion solutions look elegant to me then compared to loops. Here is a straight-forward approach. I echoed the file names and directories to keep track of whats going on. I am not ffmpeg pro, I used cp instead but should work fine for your use case.

Shell script:

source=original/ 
destination=compressed/

f1() {
    mkdir -p ${destination}${1}
    
    for file in `ls ${source}${1}*.jpg 2>/dev/null` 
    do
        echo 'Original Path:' ${file}
        echo 'Compressed Path:' ${destination}${1}$(basename $file) '\n'
        cp ${file} ${destination}${1}$(basename $file)
    done

    for dir in `ls -d ${source}${1}*/ 2>/dev/null`
    do
        echo 'Enter sub-directory:' ${dir} '\n'
        f1 ${dir#*/}
    done
}

f1 ''

Terminal Session:

$ ls 
original  script.sh
$ tree original/
original/
├── f1
│   ├── f16
│   │   └── f12.jpg
│   ├── f5
│   │   └── t4.jpg
│   └── t3.txt
├── f2
│   └── t5.txt
├── f3
├── f4
│   └── f10
│       ├── f2
│       │   └── f6.jpg
│       └── f3.jpg
├── t1.jpg
└── t2.txt

8 directories, 8 files
$ sh script.sh 
Original Path: original/t1.jpg
Compressed Path: compressed/t1.jpg 

Enter sub-directory: original/f1/ 

Enter sub-directory: original/f1/f16/ 

Original Path: original/f1/f16/f12.jpg
Compressed Path: compressed/f1/f16/f12.jpg 

Enter sub-directory: original/f1/f5/ 

Original Path: original/f1/f5/t4.jpg
Compressed Path: compressed/f1/f5/t4.jpg 

Enter sub-directory: original/f2/ 

Enter sub-directory: original/f3/ 

Enter sub-directory: original/f4/ 

Enter sub-directory: original/f4/f10/ 

Original Path: original/f4/f10/f3.jpg
Compressed Path: compressed/f4/f10/f3.jpg 

Enter sub-directory: original/f4/f10/f2/ 

Original Path: original/f4/f10/f2/f6.jpg
Compressed Path: compressed/f4/f10/f2/f6.jpg 

$ tree compressed/
compressed/
├── f1
│   ├── f16
│   │   └── f12.jpg
│   └── f5
│       └── t4.jpg
├── f2
├── f3
├── f4
│   └── f10
│       ├── f2
│       │   └── f6.jpg
│       └── f3.jpg
└── t1.jpg

8 directories, 5 files

Amazing, M0hithreddy! Thank you. That was very elegant and general solution, indeed! At the same time, very concise and semantic. — BuddhiLW, May 23 '21 at 16:37

Recursively compressing images in a folder-structure, preserving the folder-structure

1 Answers1