In this tutorial, I will show you how to do an outline using only shapes! To create a good-looking outline, you don't necessarily need to use lines. A simple, basic shape can be quite effective if used properly. Let's try different options using a nice cartoon crab.
So here we have our cartoon crab image. The outline is a standard one. The width of each lines is similar and only one color is used (black, of course!).
In this drawing, a strong shadow is covering the left part of the animal. Like you can see, there is only one color on this area (black again). All parts covered by the shadows don't have an outline. The shadow is made of one solid shape.
In the world of photography, this image would be called a negative. No lines are visible. No details inside the drawing are shown. The entire crab is made of one solid shape. The outline of the character is created by the borders of this solid shape.
Another interesting example! In this image, the crab is easy to recognize. The main details like the mouth, the eyes and the pupils are visible, but there is no outline that can be seen on this character.
It doesn't really matter since the character is easy to identify. Notice, however, that I had to add a light gray tone to the eyeballs. Without doing so, it would be hard to see the eyes properly.
In this example, if we consider white being a neutral color, the outline is created by the background color. It is quite similar to the third image (the one with the black crab on the white background) but the colors are inverted.
This example is similar to the one seen previously with the exception of minor details being visible. The result is interesting for a single panel or two. But you can't really apply this technique in a 64 pages comic strip!
Finally, remember that you don't necessarily need to show the entire character! Even if our crab is partially hidden, it's still easy to recognize! However, make sure you are showing enough information to help you readers identify the character easily!
And that's it! Now you know how to do an outline without using lines, but only basic shapes (using different tones). Don't hesitate to play with this concept as you are creating new shapes and new outlines for your characters. Have fun!