Colouring illustrations with the computer

These last years the way in which colour is applied to comics has completely changed, the same way it has changed for many styles of illustration, especially for those that combine line art and coloured areas. Traditionally this kind of illustration was made in opaque watercolour (gouache), inks and other techniques, but now almost all comics and many illustrations are coloured using drawing and painting programs, especially Photoshop.

The most flexible system to colour black and white images is to use a system of layers or channels; the original outlines of the image in black and white are separated of the colour, so changing one doesn’t affect the rest. In addition, in many programs it is possible to import directly a vectorial image (for example in AI-EPS format). This image will be scaled to the wished size and converted to raster or bitmap, in order to work in it with the painting program.

The digital colouring technique admits different variants, which we will comment briefly here. In all cases, we must start with an image, normally in black and white. We must digitize it with scanner (unless we draw directly on the computer with a tablet.) Usually it will be an inked image, but it is possible to use a pencil drawing, but it takes some extra work to get a good line drawing, by tweaking the levels of the image, or its brightness and contrast. If we have prepared a series of initial sketches in pencil, it will be necessary to check out that they are no marks left in the digitized image, and to edit it if is necessary. There are special, technical pencils in a blue color which can be used to draw the sketches (non-repro blue pencils): their colour is invisible to the scanner and the photocopier or any other reprographic machine. The advantage that they have is that it is not necessary to erase: you may ink directly over the rough, then photocopy or scan it.

Para los que se dedican más profesionalmente al dibujo de cómics, deberían considerarse algunos pasos posteriores con las imágenes -referentes a separaciones de color para la imprenta, trapping, etcétera. Aquí no nos ocuparemos de estos aspectos: sólo comentaremos las ideas básicas del proceso de colorear el dibujo para obtener una página completa en color. For those who are professional comics artists, some more steps with the images —referring to color separations for the press, trapping, et cetera— would have to be considered. But here we’ll focus on the basic procedure to colour drawings to produce a finished page.

The simplest system.

We open the black and white image in in a painting program, we convert the image to the colour mode, and apply colours with the tools of the program. Disadvantage: in order to use tools such as the paint bucket, the contours must be perfectly closed: otherwise, the paint will spread everywhere. This method has the advantage of being very simple and you can use it in any program, even Windows Paint, although we immediately find many limitations.

Another simple system.

If we create a layer that contains the black outline and select it and choose multiply as fusion mode (one of the possible ways in which a layer can interact with the layers below), all its white areas will be transparent. Now, if you colour in a new layer (or as many layers as you need) below the line art layer, the drawing with the black outline will be remain unchanged while we add colour. You can jump from one layer to the other if you want; for example, you may create selections with the magic wand in the line art layer, then keep this selection and go to the colour layer and use the selection to add colour to this selected area.

Overlaying a transparent copy.

You can do something similar to the multiplying layer process with many programs. We have used this technique a lot, for example, with old versions of PaintShop Pro:

Open the image and convert it to colour, if it is necessary: Colors|Increase colour depth|16 million colors.
Now select everything (Control + A) and copy it (Control + C)
Colour the image with the normal tools of the program. What we will do will be to cover areas with color with the brush or select parts with the image with the lasso, not worrying about the lines (since we have copied the line drawing to paste above the coloured areas.)
The two parts will constitute the coloured image, with the system of separation of a contour in black and white, and the applied colours.
When we’re done with colouring, we go to Edit|Paste|Paste as transparent image. Thus the drawing in black and white pasted over the coloured part lets see through (we must make sure that the of chosen background colour then is white, so that it will be transparent)

This method is quite simple and works fine. We only must take care of one detail. We suppose that the copy done in b) will be kept in memory. But if during the process to apply color we copy some other thing to the clipboard, we will lose the black drawing! In order to prevent it from being overwritten, we can copy the drawing in a new image. Step by step: select everything (Ctrl + A), copy it (Ctrl + C) and paste it in a new image (Ctrl + V). Thus we have the security of not losing the original in black and white. It will not be bad idea to save it, just in case we decide to make a new version in different colours later.

Vectorial drawing method.

This method usually is not very commonly used for whole comics pages, with the exception of simple illustrations. In essence, it is the same method that we discuss in the article on creation of digital illustrations.

Working in layers

Open the image in black and white, convert it to full colour and next:

Open the layers palette and create a new layer.
Place the layer with the original image over the new layer.
In the original layer, with the drawing, we select closed areas with the magical wand, or selected them with the lasso or any other useful tool, or take advantage of the quick mask.
We change to the other layer keeping the selection and painting with any tool. We will not overstep the limits of the selection, even if we carelessly apply the colour with a big brush.
We repeat steps c) and d) until having everything coloured. We save it and we’re done.

Working with channels

It is also it is a method for Photoshop and similar programs: a channels palette is necessary.

Open the image and we convert it to colour (RGB or CMYK.)
Select everything (Ctrl + A) and copy it (Ctrl + C.)
) Open the channels palette.
Created a new channel and paste the selection in it.
Once pasted in the new channel we can safely erase the content of the rest of channels (the RGB or the CMYK channels.)
Paint in colour with the normal tools in the RGB or CMYK channel. The colour will not affect the black and white drawing, because it stays in a separated colour channel.
Finally save the resulting colour image.