This tutorial explains how to split patterns into channels using only Photoshop. In practically all cases HP’s vector method will give you superior results, but sometimes this method will give you comparable results with slightly less effort. These instructions also contain a mini tutorial on how to preview your results in Photoshop.

If your pattern is simple geometric shapes or contains more than 3 or 4 colors you are better off using the vector method. I’ve chosen an ornate damask style pattern in 3 colors for this tutorial because it’s the kind of pattern that is faster with this method.

1) Tile your image. The result should be a square of at least 256x256 pixels.



2) This is my starting image. For most of this process I will be working with the image in grey scale. So I went ahead and desaturated the image (Image>Adjustments>Desaturate). If I was lucky enough to have a distinctly different grey for each of my colors, I’d skip to step 6. But if it looks more like this:



So I need to back track.

3) I’ve undone the desaturate. I need to create more contrast before I proceed. I’ll start with curves. (Image>Adjustments>Curves)



That’s a little better, but I really need to make changes based on color.

4) For this I’ll use replace color (Image>Adjustments>Replace Color). The eyedropper tool is used to select the color to be altered, I’ve chosen the grey, and at the bottom of the panel I’ve used the lightness slider to darken the color. Play with the fuzziness slider at the top if your color change is affecting too little or too much of the image.



I’ll do the same for the yellows, this time going lighter.



5) I think it’s going to be contrast-y enough now, so I desaturate it.

6) Now to actually start separating colors! First, I duplicate the layer. With my new layer selected I open up the levels (Image>Adjust>Levels)



In the levels box is a little bar graph, with three distinct peaks: one for each of my greys. I adjust the sliders below this graph until all three triangles are between the rightmost and second-rightmost peaks:



7) I’ve finished my first channel now, but here’s where things get a little tricky. If I just redo step 6 to isolate the midtone grey both the midtone and the lightest grey will be white, which I don’t want. I need to get the lightest tone out of the picture.

I grab the magic wand tool and set the tolerance to 0. I click in the black area of my image. Then I select similar (Select>Similar) and inverse it (Select>Inverse). I hide the layer with my first channel on it, so I can see my original grey scale image, it should look something like this:



I only have three colors so its okay if I just work right on this image, but if you have more colors you should duplicate the layer again and work on the duplicate.

8) I grab the pencil tool, set it to the largest size, and make the color black. I click it over the image a few times, this makes everything within my selection turn black. I get rid of the selection (Selection>Deselect).

9) I open the levels panel again, and move the sliders to isolate my midtone grey.



10) You may have noticed that this image has a lot of artifacts in it. Those artifacts are what makes this method inferior to the vector method. But, because I’m only doing a few colors cleaning them up by hand is relatively quick.



10) If you have more than three colors you will need to repeat step 7, 8, and 9 for each additional color.

11) The last color should be solid white.

12) Now I want to know of if these channels look how I want them to look. It is pretty easy to set up a test in photoshop. First I hide all the layers I’m working on. Then I select either the pen tool or the rectangle tool and set the tool options to look like this:


Next I’m going draw a random box for each of my channels anywhere in my workspace. It’s not important what they look like, but when I’m done my layers panel should look like this:



13) See how I have three new layers each with two boxes? I grab the second box on each layer and drag it to the trash can. Each time it will ask me if I want to delete the vector mask, I click yes. The layer panel now looks like this:



14) I now want to add a raster mask to each of these layers. That’s done by selecting each layer then pressing the mask button at the bottom of the layers panel. It’s the one that looks like a dark rectangle with a light circle cut out. Now the panel looks like this:



15) I now need to copy and paste each of my channels into one of these layer masks. I make my channels visible (I won’t be able to see them in my document because the new layers are on top of them, but that’s okay. I select the topmost channel layer, hit ctrl+A to select all and ctrl+C to copy it. I then enter the mask on the topmost layer by alt+clicking it (the box on the right). When I hit ctrl+V it should paste my top channel into the mask. I do this for my other channels as well. The end result should look like this:

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16) Now if I double click the first box on each layer it will bring up the color picker. I can use this to get a good idea of how my channels are working together. I fiddled with all three boxes and got acceptable results:



17) If my colors were not lining up correctly I would play with the curves. If the edges looked too hard I’d try the reduce noise filter (Filters>Noise>Reduce Noise).

18) Since I’m happy with these I’m going to go ahead and reduce the image size to 256x256. I can now use these source images for HP’s tutorial.