Can I use photoshop or illustrator to turn a simple drawing to polygons?

September 21, 2023 1:16 PM

I would like to take a simple four colour drawing (limited to 4 colours using the mode-indexed colour thing in photoshop with no dithering). Not every line is straight. I want every line to be straight. Turn it into a straigh-line only drawing with lines being at least .5 cm (let's say) long. Is there a simple way to do this in photoshop or illustrator? Alternatively, is there a name for this that I can use to google an answer?
posted by If only I had a penguin... to Media & Arts (14 answers total)

Illustrator's Image Trace function will turn your photoshop drawing into vector art. You can tell it to limit the color palette so it doesn't generate more than the four colors you used. But there's no way to tell it to make lines more than a specified length — t does what it needs to do. You can adjust how accurate you want it to be, but it's not going to straighten out lines for you. But depending on how many there are, that could be a pretty quick manual task.
posted by jonathanhughes at 1:27 PM on September 21, 2023

Response by poster: How do I generate line art, even with curves? How do I turn it into just outlines?
posted by If only I had a penguin... at 1:31 PM on September 21, 2023

That's what Image Trace does. It turns raster/pixel-based things into vector things. Once you get the vector output, you can adjust all the lines individually.
posted by jonathanhughes at 1:34 PM on September 21, 2023 [1 favorite]

How complex is the shape? No, lie. Often when we get raster art from clients that we need to cut out on the CNC for sign projects we end up tracing the object by hand in either AI or AutoCAD.
As for search terms you are trying to convert a raster image into vectors.
You can use the trace tool in AI to automate it, but results can vary depending on how much time you put into dialing in the options and the quality of the source image. It almost always involves a lot of manual cleanup in my experience, however.
posted by MrBobaFett at 1:43 PM on September 21, 2023

Response by poster: I don't just want to vectorize it (in fact, I'd be fine with not rasterizing it and leaving it as pixels), I want to make all the lines straight. No curves. I tried using the line tool in photoshop to do this by essentially tracing it with the closest approximating lines, but it's not as simple as it seems because either the lines are paths (not pixels) or if pixels, its seemingly impossible to control width/colour etc. They also have a tendency to end up in different layers which is super annoying.
posted by If only I had a penguin... at 3:18 PM on September 21, 2023

Try Geometrize. It's fun to play with.
posted by srednivashtar at 3:23 PM on September 21, 2023

OK, Maybe I'm misunderstanding what you are trying to do. Can you show us the image you're working with? What is the goal of converting to polygons, is it just a visual/aesthetic thing?

When I hear lines I assume you mean vectors and polygons to me imply closed vector shapes.
Vectors can be straight, arcs, or splines.
If it's already pixels then it's already a raster.
posted by MrBobaFett at 4:36 PM on September 21, 2023

"I want to make all the lines straight. No curves."

You can do this in Illustrator after you convert it with Image Trace. It's just not going to be automatic.

Although now I'm wondering if you mean you want to convert a curve into a series of short straight lines that still follow the shape of the original curve.

Regardless, this would be far easier in Illustrator than Photoshop.
posted by jonathanhughes at 5:40 PM on September 21, 2023

Response by poster:
Although now I'm wondering if you mean you want to convert a curve into a series of short straight lines that still follow the shape of the original curve.

This!!

And this is the image.

And the purpose would be to make a picture-pieced quilt of that image. Yes, I am crazy. Yes, I did recently say in another thread that I have 0 sewing experience. I am prepared to fail. But step one in making the pattern woudl be to get those lines straight. I was happy to do it by "hand" drawing lines in photoshop but I can't figure out how to get the lines to stay drawn the way I want them.
posted by If only I had a penguin... at 5:49 PM on September 21, 2023

Best answer: Trace the image in Illustrator by hand (ie not using the Trace function) by clicking points and holding down shift key so lines are straight. Slow and simple.
posted by TWinbrook8 at 6:02 PM on September 21, 2023 [1 favorite]

TWinbrook8 has it. Honestly easier to do by hand rather than deal with the mass of points added by image trace. See, for instance, this tutorial (and many more that come up when searching "low poly illustrator tutorial"). You don't have to necessarily do triangles (that's specifically for the "low poly" look), and you probably will want to skip the "eyedropper the colours to fill the triangles" stage and just keep the strokes on the shapes, instead.
posted by sailoreagle at 6:19 PM on September 21, 2023

Got it. Yeah unless you want to spend thousands of dollars a specialized vector software. I would trace it in AI or InkScape using the original raster as a reference layer. It will give you the best creative control. Even when I've used automated vector conversion software I almost always have to clean it up by hand.
posted by MrBobaFett at 6:19 PM on September 21, 2023

So, do you want an image that is made up of irregular polygons and/ or triangles? Like the images on this page, ignore the code and text, I'm only asking you about the images.
posted by unearthed at 2:30 AM on September 22, 2023

Response by poster: No...picture more an image like stained glass but with only straight lines.
posted by If only I had a penguin... at 4:24 AM on September 23, 2023