Who has suggestions or tips to generate Andy Warhol kind of results?
Warhol's prints were silkscreen prints. A photographic image was transferred onto a screen mesh with light sensitive emulsion. So this generates the high contrast black and white part of the print. A series of hand cut masks were then generated for the individual color areas of the print.
"In August 62 I started doing silkscreens. I wanted something stronger that gave more of an assembly line effect. With silkscreening you pick a photograph, blow it up, transfer it in glue onto silk, and then roll ink across it so the ink goes through the silk but not through the glue. That way you get the same image, slightly different each time. It was all so simple quick and chancy. I was thrilled with it."
So the question is how do you duplicate those components of the over all process. You can use the Threshold image operation effect to emulate the high contrast black and white part of the print. Or you could use something like the BW Soft Threshold adjust operation. If you are overlaying on top of colored regions, you could use the Min composite option to overlay.
As far as the colored regions in a 'pop art' style print. Warhol's approach was to use hand cut masks. Hand selected ink colors were then printed using the various region masks. Part of the design philosophy is that you can run a series of different prints, using different colors for the hand masked print passes with different successive prints.
If you wanted to really emulate Warhol's approach, then you would either hand paint or use region selection to build a set of area masks. That would then be used as different selection masks. You could then use masking to print solid color with the different region masks. And then Min composite your hard contrast black and white image on top of the laid down colored regions.
Or, you could build a squeegee paint preset, and use that paint preset to hand paint in the ink overlays for the different masked areas. We had a discussion about emulating squeegee paint tools here on the forum at one point.
Of course most people probably want to just come up with a way for the hand cut colored region areas to be generated automatically. You could use the Vectorizer or the Color Simplify or Color Quantize ip ops to do that.
Here's another description of this kind of process that was an answer to a previous question about this topic:
If you are specifically interested in Warhol's silk screen print style:
He would hand cut silk screen masks for the colored areas of the prints. That would be overlaid with a high contrast black and white photo silkscreen of the image. The high contrast overlay you can achieve via min compositing a black and white threshold of the source image. You cold play around with hard threshold or soft thresholds. The actual threshold value is going to depend on your source image. There is a Threshold image operation effect, as well as BW Threshold interactive adjust effects.
You could emulate Warhol's manual silk screen masks by either hand painting areas of the canvas with a flat color. Or selecting a portion of the image and then filling with solid color. You can use the source onion skin to aid you in performing this manual step (it displays a transparent source image to use as an aid when drawing or selecting).
If you want to do things fully automatically, then you need to emulate the manual silk screen mask generation using some kind of image processing effect. Color Simplify is one way to approach this. Color Quantize is another option. You can use the Recolor Random Hue Mean option for the Variation control in the Flat Region Colorize ip op to recolorize a simplified flat color representation generated by something like the Color Simplify ip op or Color Quantize ip op effect.
The automatic approach is not going to be as artistic as manually defining the color masks for your source image. So if you really want to emulate Warhol's style, then that part of his artistic process is important to emulate.
I just did a series of rotoscoped videos in a Warholish style for an upcoming video projection project. My best results came from exploring MSGs and then combining with Vectorizer effects in a multi-layer PASeq. There was one MSG in particular that worked almost right out of the box(found via evolver). Of course going for art rather than copying I kept tweaking until I got the effects right for the project. But I'll dig around when I have more free time and see if any of the very Warholish stuff is still intact.