thumbnail for PDF/text file in ubuntu

[arunmagar]

Hi

I want to know how the thumbnail is created for pdf and text files in linux.
As we all know in Ubuntu text files icon(thumbnail)is created dynamiclly depends on file content.
It shows files first four lines as a icon.As File content changes for first four lines the icon also changes.
Also same is for PDF file.It shows first page as a icon(thumbnail).

If anyone know how this works,Please help me.

Thanks in advance.

[minthaka]

It's quite an easy a task:
Create PDF thumbnails using ImageMagick on Linux | Prashanth Ellina

[reed9]

I think the poster is asking how the program which creates/displays thumbnails works, not how to make a thumbnail.

I don't know specifics. In general, file managers either have built in functions or use external programs that can read the particular file format and create a small image from it, which is then cached in some hidden directory - I think usually in ~/.cache. But wherever they are, they filemanager can look there for the images to display.

[reed9]

Here is some info on XFCE's file manager, Thunar, and its thumbnailers.

thunar-thumbnailers [Xfce Goodies]

And GNOME
Installing a Thumbnailer Program