jMort Tutorials: Coloring Line Art, Part 1
Hi,
I'm John Mortenson and this tutorial will explain how to use Photoshop to colorize your scanned line art.
Students in my classes often ask me how I create the colored drawings on this web site. I use Adobe Photoshop, of course! I have been using Photoshop to colorize my artwork for many years, now, and I even wrote a small course book about the subject. But believe it or not, there was once a time when I found it nigh impossible to use the computer with my artwork. Everything that I have learned about computers has happened after I left college and entered the working world, if you can imagine that. In college, I would have been hard pressed to use Microsoft Word. HA!
My early attempts at using Photoshop to color my pictures were problematic because I found it nearly tricky to paint with the mouse. Second, I didn’t find any easy way to fill in the tiny gaps for images that had lots of intricate line art, such as images with cross hatches or lots of squiggly little lines. But I have since learned to overcome both of those problems.
Now that I know how to use Photoshop more effectively, I rarely create artwork that isn't edited with the computer. The computer offers much greater flexibility at every stage of composition as well as the ability to create effects that would be very difficult- and time consuming- using traditional methods. Much as George Lucas has said that he feels "liberated" by digital editing in making the new Star Wars movies, I feel liberated to create all new kinds of artwork with the help of the computer.
Are you excited yet? Then let's move on to the tutorial!
You will need...
Your Artwork |
A Scanner |
 |
 |
| A computer with Photoshop | A Digital Tablet |
 |
 |
Digital Tablets
Though it isn't absolutely necessary, I recommend
using a digital tablet when coloring. It can be much easier
to paint with the Brush tool than a mouse and simulates the motion
and feel of a regular pen. It does take a little bit of getting
used to at first, but it is definitely worth the investment. If you'd like to find out more about digitizer tablets,
check out the Wacom website. I currently use a Wacom Bamboo tablet.
Scanning
I am going to assume that you have already created your line art. So the first step for us is to scan your inked artwork into the computer.
A: In general, I would recommend inking your artwork. Inking (and erasing the extra pencil lines) produces clean, crisp line art. The high contrast of black on white is much easier for the scanner to accurately capture than the mid-to-dark grays normally produced by pencil sketches.
On the other hand, you could scan your pencils to give your artwork that pencil texture and feel for stylistic reasons (such as the image at right). However, be aware that a scanner will usually pick up all of the smudginess inherent in pencil drawings and magnify it. Pencil lines can range from dark to light, depending on how hard you press when you draw, but the scanner may not pick up lightly penciled details. Or if it does, it may also pick up other details you don't want. Generally, you should scan a pencil drawing as a black and white photograph, which tends to make a background appear darker than pure white.
I realize that it may take some practice for a pencil sketcher to get used to inking to become proficient at it, but it's a good skill to cultivate.
When you scan an inked image, you may want to use the Line Art setting on your scanner instead of Color Photo or any other setting. The "Line Art" setting will produce a high contrast image that is composed solely of black and white pixels- no gray or colored pixels. They will appear in the "Bitmap" color mode in Photoshop (not to be confused with the "Bitmap" file type -*.BMP). It is also a good idea to scan the image in at a relatively high resolution- at least 300 ppi or more. Curved lines in the Bitmap color mode are much more likely to show stair stepping if the image does not use a very high resolution. You can lower the resolution later as necessary once you have added color and are ready for final output.
Coloring
Now that your image is successfully scanned into the computer,
you will change the scanned image from Bitmap to Grayscale color
mode, and then from grayscale to RGB color. Choose Image > Mode > Grayscale, and click yes for "1 to 1"
ratio. The file size will increase since the Bitmap mode
only had 1 bit (2 colors- black and white). Grayscale has many
more color options... 256 shades of gray from solid black to solid
white, which transaltes to 8 bit color. It's a good idea to distinguish
what is meant by grayscale and black and white since they are
not synonymous in this context.
Q: What are bits? A: The number of bits is related to the number of colors that you're working with. Computers are binary creatures... zeroes and ones, on and off, etc. Because of this, certain numbers crop up all the time on computers. Numbers like 128, 256, 512, 1024, etc. These numbers are all powers of the number 2. Two to the seventh power equals 128, Two to the eighth power equals 256, and so on. That exponent is the number of bits. The more bits you have, the more steps there are between in the range of colors that you are working with. If you work in Grayscale, you are working with a single black channel that is 8 bits, or 2 to the 8th power number of colors (which is 256). There are 256 shades of gray in a Grayscale image. In RGB, each of the three color channels (red, green, and blue) has 8 bits, and since there are three of them, you have a total of 24 bits. 2 to the 24th power is approximately 16.7 million colors.
Choose Image > Mode > RGB. You cannot change a scan directly from Bitmap mode to RGB color mode- you have to go through the grayscale mode first. The image will not appear to change much, but the colors will now be made up of RGB values. Since the image now has three channels each with 8 bits, the image data will require three times the amount of memory, of course, but you'll be able to add color.
Q: What are channels? A: Channels are the base ingredients used to form each color you see. For example, all TV screens represent color by using combinations of overlapping red, green, and blue colored lights. Using combinations of just these three colors, they can produce all of the colors you see on the screen. Most printers use a combination of four colors: Cyan, Magenta, Yellow, and Black, to create every printed color you see. The three colors of the tv screen (RGB) are the color "channels." Print images generally use four color channels (CMYK). You can think of channels as the ingredients in a cake... red is the sugar, green is the flour, blue is the eggs, etc. If you take any one slice of pie, it will have varying amounts of each component
We will use channels to make a selection.
At this point, if you were to use the Brush
tool to add color, you would have a very difficult time trying
to paint without covering over the lines of the line art. In order
to be able to paint your image without covering the lines, you
must find a way to paint over the white parts of the image without
affecting the black line art.
There are a few ways to do this, but we will use the most versatile
method. You will copy the black lines of the line art and reproduce
them alone on a layer above the background layer. What are currently
the "white parts" will appear transparent and only the
black lines will appear on the layer. The background layer will
be a white canvas, and sandwiched between the white canvas and
the line art with transparency will be a layer exclusively for
adding color.
Click on the New Layer button in the Layers palette three times to make three new layers above the Background layer with the original scan.
Now you will duplicate the line art. Click on the Background layer in the Layers palette.
Click on the Channels palette tab.
Hold down the CTRL or Cmd key and click on any one of the 3 color channels (for example, Green). By holding theCTRL or Cmd key and clicking on the channel, you have selected everything on that channel that uses any of that color for example, any green). As it is, all of the white areas use 100% green and all of the black lines use 0% green. You will use this selection to duplicate the line art layer in black on a new layer. The selection will remain active through the next several steps.
Click on the Layer palette tab.
Click on Layer 3. This is the layer you will put the line art on.
The selection is 100% in the white areas and 0% in the black areas. You will want to reverse this in order to be able to duplicate the black line art so you will inverse the selection. Choose Select>Inverse (Keyboard Shortcut: CTRL Shift I or Cmd SHIFT I).
You will need black to be the foreground color. If you need to set black as the foreground color, press the D key to restore the default colors.
Choose Edit>Fill and "Use Foreground color" (Keyboard Shortcut: ALT/Option DELETE). If you do this correctly, you will probably not see much of a difference in the image yet. The line art may appear to be slightly thicker than before. You will see the results of this action shortly.
You no longer need the selection marquee. Choose Select>Deselect (Keyboard Shortcut: CTRL/Cmd D).
Rename Layer 3 as "Line Art." Assigning layer names will help you keep track of the various layers.
Click on the eye icon next to the Background layer. Now you can see the checkerboard background through the black line art indicating the transparent spaces.
Click on Layer 1 in the Layers palette. You will add a plain white background on this layer.
Since white should be the default background color in the toolbar, you can choose Edit>Fill and use the Background color for the fill (Keyboard Shortcut: CTRL/Cmd DELETE. The layer fills with the color white. The image may appear exactly as it did before, which is the desired effect.
Rename the layer "White Background." You will leave the original image below the white background undisturbed for later reference if necessary.
Click on Layer 2 in the Layers palette.
Rename the layer Color. Now you are ready to paint on this layer with whatever color you want. You can use the Magic Wand tool and Bucket tool with the "Use all Layers" checkbox checked for making easy selections. Remember, the layer you are on is empty, even though you can see the line art above and the white background beneath. Some areas cannot be painted with the Magic Wand tool or Bucket tool, but you can use the regular paint brush on the "Color" layer to color areas that have lots of lines (like the jeans or the plaid shirt in this picture).
If you can imagine the stacking order of the layers, it would look something like this...
- Line Art
- Color
- White Background
- Background (original)
You do not have to worry about painting over the line art, and you'll always be able to see through it to the colors or the white canvas below. You now have a very easy way to color your line art in Photoshop!
Keep in mind that if you want to post to the Web, a high resolution line art scan will be too large, so you should make a copy that is smaller (use the Save for Web command if you have Photoshop version 5.5 or above and enter a smaller size in the File Size tab).
The Book
There are many other tricks that can be applied to line art illustrations which I detail in my book, "Creating and Enhancing Illustrations Using Photoshop 5.5" (Element K Press, 2000). I would also highly recommend Creative Photoshop: Digital Illustration and Art Techniques by Derek Lea.
Hope this helps!