A lot of people have expressed desires to learn how to pixel icons or have said that they would like to improve their skills. While I'm so detail-oriented that I find it difficult to explain my process, I thought I'd give it a try for you guys. I hope it helps.
And so, without further ado, I present to you...
Pixel Icon Tutorial Part 1: The Outline!
1. CREATE YOUR SIZE LIMIT.
Sometimes when you're pixelling, you don't have a size limit; you can make it as large or as small as you like. However, a deviantART icon must be 50x50px in size.
I personally like to make a 52x52px square outline on my canvas. The outline is one pixel wide on each side, leaving a 50x50px area in the middle for me to work in (one pixel for each left and right = two pixels, and 52-2=50, see?), but that's my preference.
(The outline will not be part of the actual icon!)
Some people like to work on a canvas that's only 50x50px, but I personally like to have a big canvas and just crop it later.
2. SKETCH YOUR IDEA.
Even if you think you know exactly what you're doing, I find it very, very useful to sketch my idea out so that I know I have the right size. Since 50x50px is pretty small, don't try to squeeze too many details in, and especially not on the sketch. You can add small details later when you're doing the actual outline.
I like to use a light blue and purple for my sketch, but use whatever makes you happy! ^u^
I want to do something simple for this tutorial and I have Easter on the brain, so I'm drawing an egg. Since it will be the only thing in the icon, I'll make it pretty large.
I can't instruct you on how to get the proper brush type and size for pixelling in your program, but for GIMP 2.6, I use the Pencil tool, default Circle (11) brush, all Brush Dynamics unchecked, and a Size of 0.1. Same for the Eraser tool.
I zoom in to 800% (or as much as possible) when pixelling, but those images would be too big for the tutorial. When you are pixelling, your pixel will be much larger than my large example above.
My examples will be shown at 300% zoom and at 100% view.
3. PIXEL THE OUTLINE.
This is, in my opinion, the most important step in pixelling, and unfortunately it's also the hardest to teach. After a while, you learn when it's okay to break the rules, and you start to get a 'feel' for what looks right and what doesn't.
I'll show you a couple examples of what to avoid doing as well as demonstrate lines that look 'almost, but not quite right' compared to 'that looks perfect'. This part may take a lot of practice, so don't get discouraged!
I like to keep my sketch on a separate layer, lower the opacity, and do the outline on a new layer on top of it, in a darker color. You can change the outline color at any time, so don't worry about choosing the right color right now.
Symmetry is important for an egg, but this outline is so jagged and messy! It's not clean at all and not particularly visually appealing. See all those rough corners where the outline is more than one pixel wide? In nearly all cases, you only want your outline to be one pixel wide at all points.
Zoomed in, the outline looks great... but when you zoom out, you notice that part of it doesn't look right! Perhaps the sides are too straight and should be more curved, or the curve at the tip isn't dramatic enough, or the bottom is too flat. If it looks 'off' to you, it probably is, so do what you can to fix it!
In the example above, the top third of the egg has a jagged edge, where the curve isn't smooth. See how that long line of single pixels is interrupted by a two-pixel-high straight line? That's what caused the jagged part. The bottom left and right of the egg could probably be a bit rounder, and the tip a bit narrower.
Through a series of trial and error, and moving the egg into the center of the outline, we come up with our final product. I actually ended up scrapping the outline above and started completely over again with a revised sketch, because I realized that the initial sketch itself wasn't quite egg-shaped, which meant that if I based my outline off of it, it would be difficult to make quite right.
And with that... Part 1 of this tutorial is finished! Part 2, "Coloring and Shading," is up next.