How to convert pptx files to jpg or png (for each slide) on linux?

After Installing unoconv and LibreOffice you can use:

unoconv --export Quality=100 filename.pptx filename.pdf

to convert your presentation to a pdf. For further options look here.

Afterwards you can - as already said above - use:

convert -density 400 my_filename.pdf -resize 2000x1500 my_filename%d.jpg

to receive the images.

Not sure about libreoffice, but afaik its the only program to deal with pptx files.

I found this http://ask.libreoffice.org/en/question/23851/converting-pptx-to-pdf-issue/

If you have pdfs you can use imagemagick to output any quality pictures

Convertion PPTX to PNG/JPG

This solution requires LibreOffice ( soffice ) and Ghostscript ( gs )

sudo apt install libreoffice ghostscript

Then two steps:

soffice --headless --convert-to pdf prezentacja.pptx

gs -sDEVICE=pngalpha -o slajd-%02d.png -r96 prezentacja.pdf