[feature request] Allow the user to set template for output images when using "PDF to Images" (reason: have leading zeros in the filename)

[rodrigo-morales-1]

In version 9.0.1 of PDF Converter , when the user uses the feature "PDF to Images" and the PDF has more than 10 pages, the numbering for the created images doesn't have leading zeros which makes file explorers that don't support natural sort order to list the files disorderly.

Here's an example: I used the feature "PDF to Images" on this PDF file: https://www.gnu.org/software/emacs/manual/pdf/emacs-xtra.pdf The application successfully converted the 60 pages of the PDF to images. The only problem is that the filenames didn't have leading zeros and the file explorer that I prefer using doesn't support natural sort, so the output images were shown in the following order:

emacs-xtra_1.png
emacs-xtra_10.png
emacs-xtra_11.png
emacs-xtra_12.png
emacs-xtra_13.png
emacs-xtra_14.png
emacs-xtra_15.png
emacs-xtra_16.png
emacs-xtra_17.png
emacs-xtra_18.png
emacs-xtra_19.png
emacs-xtra_2.png
emacs-xtra_20.png
emacs-xtra_21.png
emacs-xtra_22.png
emacs-xtra_23.png
emacs-xtra_24.png
emacs-xtra_25.png
emacs-xtra_26.png
emacs-xtra_27.png
emacs-xtra_28.png
emacs-xtra_29.png
emacs-xtra_3.png
emacs-xtra_30.png
emacs-xtra_31.png
emacs-xtra_32.png
emacs-xtra_33.png
emacs-xtra_34.png
emacs-xtra_35.png
emacs-xtra_36.png
emacs-xtra_37.png
emacs-xtra_38.png
emacs-xtra_39.png
emacs-xtra_4.png
emacs-xtra_40.png
emacs-xtra_41.png
emacs-xtra_42.png
emacs-xtra_43.png
emacs-xtra_44.png
emacs-xtra_45.png
emacs-xtra_46.png
emacs-xtra_47.png
emacs-xtra_48.png
emacs-xtra_49.png
emacs-xtra_5.png
emacs-xtra_50.png
emacs-xtra_51.png
emacs-xtra_52.png
emacs-xtra_53.png
emacs-xtra_54.png
emacs-xtra_55.png
emacs-xtra_56.png
emacs-xtra_57.png
emacs-xtra_58.png
emacs-xtra_59.png
emacs-xtra_6.png
emacs-xtra_60.png
emacs-xtra_7.png
emacs-xtra_8.png
emacs-xtra_9.png

I understand some users might prefer to have leading zeros in the index of each screenshot, while others not, so I think it would be convenient if the window "PDF to Images" showed an input box to allow the user to set the filename template for the output images so that the user can adjust it to his/her needs.

For reference, ImageMagick's convert allow the user to set the template for output images in the command line as shown below:

cd ~/Downloads
convert emacs-xtra.pdf 'output-%03d.jpg'

find ~/Downloads -type f -name '*.jpg' | sort

/home/rodrigo/Downloads/output-000.jpg
/home/rodrigo/Downloads/output-001.jpg
/home/rodrigo/Downloads/output-002.jpg
/home/rodrigo/Downloads/output-003.jpg
/home/rodrigo/Downloads/output-004.jpg
/home/rodrigo/Downloads/output-005.jpg
/home/rodrigo/Downloads/output-006.jpg
/home/rodrigo/Downloads/output-007.jpg
/home/rodrigo/Downloads/output-008.jpg
/home/rodrigo/Downloads/output-009.jpg
/home/rodrigo/Downloads/output-010.jpg
/home/rodrigo/Downloads/output-011.jpg
/home/rodrigo/Downloads/output-012.jpg
/home/rodrigo/Downloads/output-013.jpg
/home/rodrigo/Downloads/output-014.jpg
/home/rodrigo/Downloads/output-015.jpg
/home/rodrigo/Downloads/output-016.jpg
/home/rodrigo/Downloads/output-017.jpg
/home/rodrigo/Downloads/output-018.jpg
/home/rodrigo/Downloads/output-019.jpg
/home/rodrigo/Downloads/output-020.jpg
/home/rodrigo/Downloads/output-021.jpg
/home/rodrigo/Downloads/output-022.jpg
/home/rodrigo/Downloads/output-023.jpg
/home/rodrigo/Downloads/output-024.jpg
/home/rodrigo/Downloads/output-025.jpg
/home/rodrigo/Downloads/output-026.jpg
/home/rodrigo/Downloads/output-027.jpg
/home/rodrigo/Downloads/output-028.jpg
/home/rodrigo/Downloads/output-029.jpg
/home/rodrigo/Downloads/output-030.jpg
/home/rodrigo/Downloads/output-031.jpg
/home/rodrigo/Downloads/output-032.jpg
/home/rodrigo/Downloads/output-033.jpg
/home/rodrigo/Downloads/output-034.jpg
/home/rodrigo/Downloads/output-035.jpg
/home/rodrigo/Downloads/output-036.jpg
/home/rodrigo/Downloads/output-037.jpg
/home/rodrigo/Downloads/output-038.jpg
/home/rodrigo/Downloads/output-039.jpg
/home/rodrigo/Downloads/output-040.jpg
/home/rodrigo/Downloads/output-041.jpg
/home/rodrigo/Downloads/output-042.jpg
/home/rodrigo/Downloads/output-043.jpg
/home/rodrigo/Downloads/output-044.jpg
/home/rodrigo/Downloads/output-045.jpg
/home/rodrigo/Downloads/output-046.jpg
/home/rodrigo/Downloads/output-047.jpg
/home/rodrigo/Downloads/output-048.jpg
/home/rodrigo/Downloads/output-049.jpg
/home/rodrigo/Downloads/output-050.jpg
/home/rodrigo/Downloads/output-051.jpg
/home/rodrigo/Downloads/output-052.jpg
/home/rodrigo/Downloads/output-053.jpg
/home/rodrigo/Downloads/output-054.jpg
/home/rodrigo/Downloads/output-055.jpg
/home/rodrigo/Downloads/output-056.jpg
/home/rodrigo/Downloads/output-057.jpg
/home/rodrigo/Downloads/output-058.jpg
/home/rodrigo/Downloads/output-059.jpg