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A quick question for any gurus out there :-)

Suppose I have a simple picture with a red circle, a blue square and a green triangle. The background is yellow. Those are the only 4 colors involved.

Is there are a program out there that can read in the picture and split it into 4 layers, based on color?

If I were to hide the "red" layer then the circle would disappear, etc.

Forget about hues and shading. Just a simple picture with only 4 colors.

Many thanks,

Pete

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Here's how to do it in Photoshop:

1. Select the Magic Wand tool.

Depending on the quality of the image, you may have to play around with the tolerance (can be found along the top of the window) to have the wand select the color you want. 0 tolerance means that the wand will select only that specific color with no wiggle room for other shades. 30 will probably be a good starting level.

2. Using the Magic Wand, select a shape.

3. Cut, using Ctrl+x (Command+x on Mac).

The shape will disappear, leaving a hole in your image.

4. Paste in place using Ctrl+Shift+x (or Command+Shift+x)

This will create a new layer with your shape.

5. Repeat for each shape.

6. Hide all shapes, fill in the holes with eye-dropper.

If you need the background to be one solid color without those holes where your shapes used to be, use the wand to select the holes and fill them with the eyedropper.


This will work best if your colors are truly uniform and solid, otherwise it might be hard to get well-defined edges. What you want is a pretty basic thing so most other graphics editors will be able to do this with a similar process. If you wanted an automatic process that does all of that automatically, I don't know if I have the answer. Illustrator's image-trace would be the closest thing that I could think of, but even then you'd have to separate each part into layers and fill in the gaps.

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"Forget about hues and shading. Just a simple picture with only 4 colors."

Unless your shapes don't have any curves (or have curves and look jagged and bad), it does not really have only 4 colors. Use the zoom up to look at a curve you will see something like this for a green circle on yellow:

enter image description here

Hues and shading inside the objects you want to separate wouldn't actually make it that much harder. You can just lasso big areas with the selection tools. It's only the edge that's hard, and that edge is made of hues and shades.

Justin explained how to try and get Photoshop to help you by finding an edge automatically, but it's not possible to do perfectly. I don't have a better answer but wanted to point out that what you want to do isn't as easy as it sounds.

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