Vectorise images using Python (Spark)

I have a large series of jpeg/png images. I want to eventually run a neural network on these. However first I have to vectorise the images. Because there is a large volume of images, I plan to use python and Spark instead of software.

I'm a beginner programmer. Would anyone know some rough code to do this? Failing this, alternative methods would also be very welcome!

Many many thanks in advance!