How to make transparent background in clip studio paint

This basic how-to describes my process for adding colour to what would otherwise be black-and-white scanned line art. First, you’ll find instructions for Photoshop, then Clip Studio Paint. A reader asked how I do this, and it’s a pretty common thing to want to do, but the method is not always obvious. Note: the most typical use case for this is scanned line art, where you’re starting with an image that is made of black and white pixels; black lines on a white background. We’ll separate the lines from the background, then use “transparency lock” to let us colour the lines. If you’re already starting with line art on a transparent background, just skip to the “transparency lock” bit.

Above, you can see a panel where I've applied colour to a significant portion of the linework. That's the original line art on top, and that's the finished panel below it. Below, I've isolated JUST the line art layer, to show it more clearly.

I'll take a little snippet from the original scan for this panel to use as a demo.

It's just a black-and-white image (though the file is currently set to RGB) on one layer ("Background"). Let's go!

Create a selection from the line art. In the Channels palette, command-click the RGB or Grayscale thumbnail to load that image information as a selection.

You'll see marching ants to show that a selection is active. Importantly, we need to "invert the selection" now. To find out why, just follow these steps without inverting the selection and you'll see.

Make a new layer. In the Layers palette, add yourself a new layer. This will become your new "Line Art" layer.

Invert the selection. Use the menu Select > Inverse, or hit command-shift-I (by default, I think).

Fill the selection with colour. On your new "line art" layer, use the Fill command to fill the selection with whatever colour you want. Use black, use pink, use whatever.

Initially (assuming you use black), it'll just look like your line art has become more intense. But if you hide the background layer now, you'll see your new "line art" layer has your line art on it. The liney parts are solid and the white parts are transparent. Good. Great. That was the goal.

Turn on Transparency Lock. On the Layers palette, click the little checkerboard-looking toggle.

That's basically it. Choose a wacky colour and try painting on your new "line art" layer. You'll see that Photoshop only lays down colour based on the existing opacity of the pixels that represent your line art, i.e., you'll be colouring your line art.

I set all those steps to run in an Action, so I can knock out that line art with one button press. I encourage you to do the same!

But what about Clip Studio Paint?

In CSP, there's this one little menu item to do basically the same thing: Edit > Convert brightness to opacity. Select a layer, hit that menu item, and you're set.

I ran that menu command on the same file, below. All that's left is to click the little Transparency Lock toggle, same as in PS, and you're off to the races.

Play around with it! A little experimentation and understanding will open a whole bunch of creative options.

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