Photoshop Action / Method for Reducing Colour Pallette?
September 13, 2020 9:43 AM   Subscribe

One thing that distinguishes (many) illustrations from (most) photographs is that illustrations have a consistent/limited colour palette. So if an illustrated book has green in, it will be a particular green (with some minor variations in shade for shadows/highlights etc.). If you look at the illustrations within the same book, they kind of "match" not just in the illustration style, but in the palette. Is there a way I can achieve this in photoshop from a photo or illustration?

It's that time of the year again when I start thinking about making a new picture book for my son. This one will be for Christmas. In the last book, I did some actions that turned photos into things that looked kind of like illustrations. I'd like to keep experimenting with this (likely with different actions), but one thing that I think keeps the illustrations from looking quite right, and keeps the book from hanging together well, is that the pictures don't really look like they match one another. And within pictures I'd like a more limited pallette too.

The next book will likely be a Christmas theme, so I would want to move things into Christmas colours. I'm thinking of some sort of actions where I could create a pallette somehow and then each picture would be like 90% or 80% (I'm not sure how much it would have to be) in some shade of the colour palette, I chose. So here are the 6 or 7 colours, take the 90% of the colours in the picture that are closest to these colours and turn into whichever of these colours they're closest to. I recognize that obviously not EVERYTHING would work well as one of a few selected colours, which is why I'm ok with having some details remain in other colours.

How would I do something like this? I assume I would want to do the illustration-making first and THEN limit the colour palette, but feel free to tell me I'm wrong.

I am also willing to have someone with actual art/design background tell me this is the worst idea ever and it would look terrible.

Note: Adobe Creative Suite and could use another program, though I'm only decently familiar with photoshop, lightroom, and indesign. If I needed to use something else I would have to learn the software first.
posted by If only I had a penguin... to Media & Arts (8 answers total) 6 users marked this as a favorite
I'm having a little trouble picturing exactly what you mean. Do you mean something like this?

Do you want them to still look like photographs?

Or more painterly verging to cartoonish?

You might want to look into the notion of "color grading" which is commonly used in movie making to give a movie a "tonal" look to it

Sorry this is a bit scattershot but I'm no 100% sure what you're after
posted by RustyBrooks at 11:02 AM on September 13, 2020

Best answer: One way is to change the image mode to indexed, which gives you the option to specify how many colors are in the image. You can choose, say, 16 colors, and it'll do its best to pick the right ones for you. If you specify a custom palette, you can tweak those colors. Setting the dither pattern to 'none' .

The 'positerize' filter can achieve a similar effect, as can a couple of the 'artistic' filters.

If you want everything in shades of the same color, then convert the image to grayscale, then back to RGB, then apply Hue/Saturation changes with the 'Colorize' option turned on. That will give you the tinted photo look that I think they're talking about.

Ultimately, if you want your image to look like an illustration, tracing it by hand in Illustrator or Inkscape is the way to go.
posted by pipeski at 11:04 AM on September 13, 2020 [1 favorite]

One way to get your palette is to find an illustration/photo that has the color range that you like, bring it into one of the online color pickers that will pull out the colors and give you a palette. (ColourLovers might do this? Sorry I’m not near my laptop).

To convert photos to various illustration styles in PS, take a look at the tutorials by the guy at Blue Lightning TV on YouTube. He has dozens of videos in a multitude of styles and his instructions are the clearest and cleanest of any tutorial provider I’ve watched.
posted by TWinbrook8 at 12:19 PM on September 13, 2020

Response by poster: I do plan to turn it to illustration style, but I already know how to do that. I'm only asking about the colour thing.

So when I go from a photo to something that looks more like an illustration, the colour in the illustration-like image is pretty much natural colour. Sometimes a little more or less saturated or the contrast changes due to outlines added, or whatever, mainly the colour stays the same. I want to limit(ish) the colours to a specific palatte (and I know how to find or create a palette The purpose of doing this would be both A) To make it a little more cartoonish-style illustration and B) To be able to have a consistent colour scheme from one page of hte book to the next to tie the book together better sylistically.

It sounds like the closest to what I want is the index function, but it sounds like that chooses the colours itself. Is there a way I can manipulate this? Like I'm thinking extend the canvas so that my image is only a tiny portion of it, then fill the extra canvas with my palette colours and then those colours will be the best choices? If I then crop out the extra canvas will that change the colours that the indexing used?

Also, since this is a colour mode, not an adjustment, I assume it's all or nothing... I can't have any original colour peak through or face the effect at all. Given this, can I create an indexed version of the image and place that image as it's own layer in an RGB document with the original image and mask or blend the images to get a little more control? Or will the indexed layer be full colour if I pull it into an RGB document?
posted by If only I had a penguin... at 2:26 PM on September 13, 2020

One thing you could do is use Inkscape or Illustrator (like pipeski suggested) but instead of tracing it by hand, you might be able to use the automatic tracing functionality which, at least in Inkscape, is pretty good (haven't tried Illustrator).

The result of tracing an image will be a vector image made up of as many layers as you specify, one for each color. (So if you have a picture of the British flag, for example, and specify 3 layers then it will (hopefully) give you an image with separate red, blue, and white layers. If you specify, say, 8 layers but there are more colors than that in the image, the tracer will pick 8 more or less representative shades.) You'll then be able to select each layer and change the color to be a specific one from your palette.

How well this works will depend on how good a fit your images are for the automatic tracing process. It'll probably work better with the illustration-ified images rather than the original photos. You might have to play around with the settings a little bit, and learn a little about how vector images work if you're not familiar with them. After adjusting your colors you could then save the image as a .png or whatever and work with it again in Photoshop if you prefer.

I'm familiar with vector software but not with Photoshop, so maybe (hopefully) there are more efficient solutions. But if not this is an option.

Good luck with this very nice project!
posted by trig at 2:45 PM on September 13, 2020

Best answer: It sounds like the closest to what I want is the index function, but it sounds like that chooses the colours itself. Is there a way I can manipulate this?

You can edit the colours that are automatically chosen. The Photoshop version I have allows has a 'custom' option where you can change each of the colours, or add more of them.

Once you convert the image mode to indexed colour, the palette information is lost. You you can certainly copy and paste the result into a full RGB file - it won't regain all of the original colours. So your layer idea would work.
posted by pipeski at 3:05 PM on September 13, 2020

Response by poster: I've been playing around with this and the one problem I'm having is that even starting with very cartoonish images already, it doesn't necessarily give me big blocks of the same colour. Instead it will give me little patches in another colour sometimes. This ends up looking a little weird. The dithering is set to 0.

I can probably live with this since I'll blend and mask (and maybe context-aware fill some of the patches away), but if anyone has any quick tips/setting changes that can tell it "I want big blocks of single colours more than faithful reproduction of slight shadows across a surface" I'm all ears!
posted by If only I had a penguin... at 7:52 PM on September 13, 2020

To build on what TWinbrook8 said, you might try playing around with Image > Adjustment > Match Color, then selecting an existing image for >Source, that has the colour scheme you're after, as a quick 'n' dirty way to colorize your new image in that palette. (These settings are from CS6, no idea if that's changed in newer versions)

Any posterizations / illo treatment would follow after this...
posted by Bron at 7:59 AM on September 15, 2020

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