Let's discuss purely technical aspects of icon making
1. Lines, slopes
One of the vital parts of the composition is the outline of the object, i.e. rough line, which separates the object from the rest of the image. When creating large-scale images, the designer occasionally thinks about defining objects with complementary outlines. This is unnecessary because of the size: even low contrast objects do not blend into a one. Pixel graphics is other story. Two solutions are available: either foreground and background colors have to be from opposite sides of the color wheel, or the foreground should be separated from the background by visible lines and shadows. I will dwell on lines deeper.
If we return more to the large scale graphics, we can note that in order to highlight contours, we can use all (including the most complex) angles, Bezier curves and borders. Anyway, the line will appear ideal thanks to anti-aliasing. When shrinking the image scale to the size of an icon, situation changes greatly. When every particular pixel is equally important and can change the overall look of the composition, anti-aliasing is simply not applicable. It comes that you have to think about the possible line slopes.
The slope you choose for the line, determines the step of this line. Because each line consists of primary elements, the union of which determines its neatness and visual appeal.
For example, a 18-degree slope consists of many tiny 3-pixel lines combined with a 1-pixel downshift:
This is how almost every line looks like. Basic element followed by joining and second basic element. However, not every slope creates lines that look look neet and not messy.
For example, here are 25 and 20-degree angles:
It can be easily seen which line is more appealing. The 25-degree slope makes a line consisting of even 2-pixel primary elements. The 20-degree slope has a basic element consisting of three parts: 3-pixel, 3-pixel and 2-pixel. The angle is more complex, thus, if not supported by additional visual effects, it creates a feeling of untidiness: the primary elements have contrast which is too obvious to escape the human eye.
Here we can see the first conclusion. The most "appropriate" angles have to make as simple primary elements as they can. therefore, the perfect slopes are 0 and 90 degrees. In those, 1-pixel primary elements are combined without downshift and form even lines. Less ideal are slopes which form primary elements of 1, 2, 3 pixel with 1-pixel downshift. Of course, the lines can not be even, but the human sight will process the image and present to the user what you intended to show to him. Also, the mentioned slopes can be considered correct (but at a stretch): angles with basic elements made of different lines shifted by more than 1 pixel.
Now we can discuss another problem. In the previous paragraph, I purposely defined angles with primary elements of 1, 2 and 3 pixels as acceptable. Such tiny lines, especially when a large number of them is joined, look like a single whole. But what do we see if we change the basic elements to 10 or 20 pixels?
Here is an example:
It can be obviously seen that the line doesn't have solidness. It is not a continuous line anymore; it is a combination of several lines, located near one another. Hardly any artist wants its creation to look that way. So, we have another conclusion: if you use small slopes, which make long basic elements, it must be justified and employed with great caution.
And, finally, the third aspect I have to mention about lines. I did write that the basic element has to be as simple as it can.
For instance, a 25-degree slope can be produced in the two (of course more of them are possible) following ways:
In the first picture the primary element is a 2-pixel line. In the other picture, it consists of three elements: 3-pixel, 2-pixel and 1-pixel. The same slope but the look is different. The complex primary element made the line messy.
Such examples can be produced for about any angle, so in your projects, try to simplify as much as possible.
It can be stated without an exaggeration that the color is the leading element of your work; not suiting or badly matched colors can kill even the most creative idea. What can we say about the color in miniature graphics?
First, there is a certain rule: if the image looks poor when reduced to monochrome, then the colors that were selected are wrong. This rule is valid not only for icons but for the entire graphic design.
Second, you will probably unable to use safe RGB. Of course, you can use GIF colors only, but this limits you greatly. Gradients, shadows, blending and many other tricks will not be accessible to you.
Third, try to enlarge the portion of "flat" color. The more evenly colored parts without blurring and jumps your picture has, the more neat it looks. Icons are too tiny and the over usage of complex filters makes the image look messy.
Fourth, gradients. This is a wonderful instrument which can improve the look of any picture. Besides visuals, gradients are an ideal solution to get rid of the "broken line" effect (lines with too long basic elements). But be careful when applying them because too many gradients can kill the flat color, and be unable to fit into the gif palette.
Fifth, shadows and flares. All aspects of applying shadows and highlights in icon making are completely identical to the rules of the general graphic design. The only thing I would like to note: create everything by hand. Don't apply filters, make all shadows and highlights in a different layer and after that edit its transparency. If applying filters, you almost never know what the result will be. It is bad when you don't control the making of a composition. It is worse if you don't control it if creating miniatures.
And, lastly, sixth. Nuancing is the key detail of icon design, which greatly affects the visual appearance of the composition. If the blue human eye in the icon is sized 1 pixel, increase the color intensiveness. For example, instead of 0, 131, 159 choose 71, 195, 242. It doesn't matter that the human eye never has such color; in the first case it will look like a gray dot, but in the second example it will definitely be a blue eye.
Thoroughly control the picture, do not let the visual tricks to spoil your design. It is OK if objects is not perfect technically, but the whole picture must be perfect.
As an example, I pictured the pack of juice located in front of me. The picture has flat color, gradients with broken lines, shades and highlights and tints.
If I talked about something bigger than pictogram creation, this chapter wouldn't fit into a whole book, but the resolution of compositions ;limits fonts too.
The resolution of symbols becomes the leading aspect as opposed to their fineness. Almost in all cases, only if not the letters are the main part of the project, the font size has to be decreased to the largest extent possible.
In general, virtually any graphic company has its own font with small characters. Such a font can be made in a few hours. You can browse the web and collect your own library of very nice fonts. First of all, I would recommend you to get the DS Pixel and Seventen 7Vedi website as well as the complete series of fonts from the Lakmus Lab website.
If you don't want a new font, tiny typesizes of Arial and Verdana will do. As a last option, you can create the needed characters yourself.
There are not many rules there. First, characters cannot be less than 5 pixels high or less than 3 pixels wide.
Second, letters should not use anti-aliasing. It turns the text into an unrecognizable mixture of pixels.
Though, there are no rules without exceptions and the 5-point Arial looks rather understandable.