I'm looking to create a "retro" effect on some images. I don't know a better name for this style, the main features of it being few colors, flat design, and bold outlines.
Some examples:
Source image: https://upload.wikimedia.org/wikipedia/commons/1/10/Zion_angels_landing_view.jpg
"Retro" style: https://s3.amazonaws.com/adg-bucket/zion-national-park-angel-s-landing/medium.jpg
Source image: http://image.boomsbeat.com/data/images/full/113727/rick-knepper-jpg.jpg
"Retro" style: https://images-na.ssl-images-amazon.com/images/I/7138b6Gz1bL.SY450.jpg
My inspiration is the posters of US national parks made in the 1930s that have a retro/vintage style to them that I'd like to recreate on my own images. What are some tools that I could use to achieve something close to this? Ideally something in script form that I could apply to a big set of images.