The set of functions you are looking for are Frappe Framework functions and not particularly ERPNext functions.
However, they are available to you for managing files even in ERPNext. To get there you should go to the Awesome Search Bar at the top of the screen of any ERPNext screen and type: File
Then select the “File List” option that appears in the drop down list. This will take you to a screen that is essentially the Frappe functions you are trying to access.
The screen displays the list of folders that currently contain your files. By using the buttons in the top right corner of the screen you can add new folders and other functions to help you manage your files.
Thanks BKM, I’m using these functionalities but the option to crop any image or optimize (compress) is not available on my site as it is mentioned in documentation link.
Hmm… I never considered that the full function set would not be available, but you are right. The crop icon is not anywhere to be found when using the file functions (even if the picture file is obviously too large for upload)!
I only attach spreadsheets so I did not notice the crop icon missing
My apologies for interrupting your question with incorrect information.
This will probably require a search in the code to find where the crop function is turned off.