Photoshop Tips: Scanning and cleaning up line drawings

I was properly introduced to PhotoShop in 1996, having taken a new job in the marketing department of a fast-growing building engineering company. I had my own desk, with a brand new Mac and the latest software – including Quark, Freehand and … PhotoShop 3. The engineers were very excited. Now the firm could produce their own brochures, and they had their own ‘graphic designer’ in house: me, a 24 year old architecture graduate, untrained in both design and software. The experienced, 40-something designer with his own design firm who was being blithely tossed aside for this set-up was not thrilled. Every few weeks, he’d call up to tell me so.

But I was overwhelmed with possibilities, poring through design magazines at night and, by day, bedazzling structural engineers with my demonstrations of the clone stamp, the magic wand and… ta dah! LAYERS.

Hooray for layers!

Layers and their many states are the most important feature of Photoshop. They’re like sheets of stacked acetate, meaning you can see through transparent areas of a layer to the layers below – and you can change the position, transparency and colour mode without losing essential information.

Which leads to the most common question I’ve been asked by illustrators who are new to PhotoShop: “How do I bring my line drawing into PhotoShop and clean it up, so that I can add colour digitally?”

There are dozens of ways to do it… but I can show you my way! The below assumes at least a working basic knowledge of PhotoShop for the reader:

First I scan my drawing – as a greyscale image at a resolution of at least 300dpi – and open in PhotoShop:


Then I open the CURVES tool under images/adjustments (some people use LEVELS but CURVES are a more flexible and powerful tool)


Note, because I scanned the image in greyscale, there is only one channel (grey). I won’t go into curves in detail, especially as the way I use them has become fairly instinctive, but if you copy how I’ve tweaked the curve below, bringing in the top (white point) and the base (black) points and raising the curve in the middle you’ll see it increases the contrast, and can get rid of most of that grey fuzziness caused by the texture of the paper.


Now I want to check if my drawing is straight, so I bring the rules across to check. It’s a bit off:


I use the transform tool to rotate the whole image a little and now it’s lined up, but there are lots of little marks (outlined here in red) – from my dirty scanner (oops) and also I want a white margin around the whole thing.


I use the clone tool and eraser tool to tidy up the small details, and the marquee tool to select the area I don’t want to the left and clear it to make a white border.


NOW – to layers and channels. At the moment the file is just one layer – the background layer. I could simply select this layer, then change the blending mode of the layer (in the layer dialogue box) to ‘multiply’ and just add colour underneath. But this could restrict me later, and is no good if I want to change the colour of the line. So I go to CHANNELS. Because the image is greyscale (eg black and white only) there should only be one channel – grey:


I hold down the COMMAND key (control on a PC) and click on the channel icon. This selects all the lighter tonal information in your image, which should now look like this:


Now, I INVERT THE SELECTION, in Select/Inverse (or keyboard shortcut COMMAND/Control + I) and make a new layer in the layers pallette:


At this point you may want to make your image RGB or CMYK – remember not to flatten your image though. Now, with the new layer selected, you can fill your selection with the colour you want your lines to be. I choose black. And so the layers pallette looks like this.


If you hide the bottom layer and zoom in on your artwork, you can see that the detail and gradation of tonal values has been maintained but, unlike what you would see if you use multiply, the rest of the layer is transparent:


I save my file at this point. And add a layer between the original scan (I like to hang on to it for a while) and the new layer containing the lines only.


And then I add another layer – for the colour:


And start adding colour – look! Of course, now I can add as many layers and colours as I like.


Clear as mud? I do hope this helps some of you. 🙂

Finally, here are a few resources. Everyone does it differently, of course: