How do I delete the white background from line art?

Over the last year I’ve been Googling the sentence above – how do I delete the white background from line art? I know that I know how to do this, but I keep forgetting. So I’ve decided to write it down so that I can reference it in future, and hopefully help others as well.

I’m using Photoshop CS5.1 on a Mac.

Technique No. 1

This is the way I was taught, but kept forgetting because it’s a string of keystrokes that if done in the wrong order doesn’t work at all.

First, turn everything off except the layer you want to cut out. In the example above you can see the white areas behind the black lines that I want to get rid of.

Duplicate your line layer, so you have a spare, and turn the original off. I like to duplicate by Alt+drag while clicking on the layer. (It took me a long time before I realised I could do that, hence why I’m writing it here!)

Next, select the entire layer (Cmd+A) and cut it (Cmd+X). Fill the now-empty layer with black (Alt+backspace).

Turn Quick Mask on by pressing Q, or selecting the button under the colour picker (as above).

Paste (Cmd+V) your line art into the layer. It should look like the above.

Press Q again to turn Quick Mask off.

Inverse the image by pressing Cmd+I.

Cut (Cmd+X) to leave the line art, like so!

The reason this is my preferred method is because it’s the best way to recolour my line art. For the purple example above I Cmd+clicked on the preview window in Layers (which selects the entire painted area on a layer) and then filled it (using Alt+backspace again) with purple.

If, however, you aren’t interested in painting the line, then you may prefer one of the other methods.

Technique No. 2

This begins in the same way as No. 1: Duplicate your line layer, copy it and cut it, fill the layer with black.

Then you select the layer, and add a mask to it using the button highlighted above (“Add vector mask”).

Alt+click on the white mask to select it.

Paste (Cmd+V) into the mask.

Invert (Cmd+I).

Click out of the mask onto the ordinary layer. As you can see above, though the line art is now free from white the background that was transparent is now black. This is easily solvable by filling in the transparent areas before beginning, but it’s one of the reasons I don’t tend to use this method. Also, there is no way (that I have yet discovered) of colouring the lines.

Technique No. 3

This is the simplest and perhaps best method if all you want to do is get rid of the white. It’s quick and requires no cutting, pasting, or inverting.

Double-click on the line art layer preview window.

The Layer Style window will pop up.

In the Blend If: Gray area at the bottom, select the top white slider and adjust it by a couple of degrees. I moved it from 255 to 253. The white background will disappear.

Exit the window and, as you can see, only the line art remains.

However, as the background still exists on the layer and is only hidden from view, it means that painting the line art is not possible.

In the past I have had problems with this method – jagged white remains in corners and so on – but recently it’s been working beautifully.

I hope this is helpful to someone out there! Please let me know if you know of other / better ways of doing this, I’m always looking to learn!