I have a bunch of pdf files, from which I want to produce a movie.
I'm using sips (on Mac OS) to convert the pdfs to .png, and then produce the movie with ffmpeg.
So far, I'm doing this:
for i in {2..9087}
do
sips -z 1024 -s format png fig${i}.pdf --out png/fig${i}.png
done
followed by
ffmpeg -qscale 5 -r 20 -b 9600 -i fig%d.png movie.mp4
However, I found that ffmpeg is struggling with the transparency of .png (it renders the movie with blured things). I've read that it is advisable to input the ffmpeg with non-transparent .pngs. So, my workflow has a flaw, since sips apparently does not have a way of exporting non-transparent pngs from pdf.
I'm wonder if anyone already solved this problem, and would like to share the solution.