Let's discuss strictly technical details of icon design
1. Lines, angles
One of the most important parts of the image is the outline of the object, i.e. rough linear marking, which limits the object from the background. When working with normal-sized graphics, the designer occasionally cares about highlighting of objects with complementary lines. This is unnecessary because of the scale: even low contrast objects do not blend into a single whole. Icon graphics is different. Two solutions are available: either object and background colors have to be from different sides of the color wheel, or the object should be separated from the background by contrast lines and shadows. I will dwell on lines deeper.
If we think more to the large scale images, we can note that in order to highlight contours, we can use all (even the most complex) angles, Bezier splines and edges. Anyway, the line will appear ideal thanks to anti-aliasing. When decreasing the image dimensions to the size of an icon, situation changes greatly. When each single pixel is vitally important and can change the whole appearance of the icon, anti-aliasing is simply not applicable. It comes that you should think about the possible line slopes.
The angle you select for the line, specifies the step for this line. This means that every line consists of basic elements, the union of which determines its neatness and esthetics.
For instance, a 18-degree angle contains many small 3-pixel lines combined with a 1-pixel downshift:
This is how nearly each line looks like. Primary element followed by joining and another primary element. Unfortunately, not each angle creates lines that look look neet and not messy.
For example, here are 25 and 20-degree angles:
It can be easily known which line is more appealing. The 25-degree angle produses a line containing even 2-pixel primary elements. The 20-degree slope has a basic element consisting of three lines: 3-pixel, 3-pixel and 2-pixel. The angle is more complex, thus, if not supported by other visual effects, it creates a feeling of messiness: the primary elements have contrast which is too strong to escape the human sight.
Now we can come to the first conclusion. The most "appropriate" angles must make as plain primary elements as they can. Thus, the perfect angles are 0 and 90 degrees. In them, 1-pixel basic elements are combined without any shift and produce smooth lines. Less perfect are angles which form basic elements of 1, 2, 3 pixel with 1-pixel downshift. Surely, the lines can not be even, but the human sight will process the image and present to the viewer what you intended to show to him. Also, the mentioned slopes can be considered acceptable (but at a stretch): angles with primary elements consisting of unequal lines shifted by more than 1 pixel.
It is the time to move to another issue. In the last paragraph, I purposely defined angles with primary elements of 1, 2 and 3 pixels as correct. Such tiny lines, especially when a large amount of them is combined, look like a single whole. But what happens if we change the primary elements to 10 or 20 pixels?
Here is an example:
It can be obviously noticed that the line doesn't have solidness. It is not a single line now; it is a combination of several lines, located near one another. Hardly any artist wants its composition to look that way. Thus, we have another conclusion: if you use minimal angles, which make long basic elements, it has to be justified and employed with great caution.
And, finally, the third aspect I have to mention about lines. I did write that the primary element should be as plain as it can.
For example, a 25-degree angle 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 lines: 3-pixel, 2-pixel and 1-pixel. The same angle but the image is different. The complex basic element produced the line messy.
Such examples can be made for about any angle, so in your projects, make sure to simplify as much as possible.
It can be stated without an exaggeration that the color is the main aspect of your work; improper or badly matched colors can ruin even the best idea. What can we write about the color in miniature graphics?
First, there is a certain rule: if the image looks poor when converted to grayscale, it means the colors that were chosen are incorrect. This rule is valid not only for icons but for the whole graphic design.
Second, you will probably unable to use safe RGB. Sure, you may select internet colors only, but this ties you hand and foot. Gradients, shadows, blending and many other effects will not be accessible to you.
Third, try to increase the areas of "plain" color. The more evenly colored parts without blurring and jumps your composition has, the more clear it looks. Pictograms are too small and the excess usage of complex effects makes the image look dirty.
Fourth, gradients. This is a wonderful instrument which can change the appearance of any project. Besides esthetics, gradients are an ideal solution to abolish the "broken line" effect (lines with too long primary elements). But be careful when using them since too many gradients can ruin the flat color, and be not suitable for the gif palette.
Fifth, shadows and highlights. All aspects of using shadows and highlights in icon creation are totally the same to the rules of the general graphic design. The only ine I have to note: create everything yourself. Don't apply filters, make all shades and highlights in a separate layer and after that edit its transparency. When applying filters, you almost never can predict what the result will be. It is bad when you don't control the making of a composition. It is awful if you can't control it if creating miniatures.
And, lastly, sixth. Nuancing is the main aspect of pictogram design, which largely affects the visual look of the composition. When the blue human eye in the picture is sized 1 pixel, increase the color saturation. For instance, instead of 0, 131, 159 choose 71, 195, 242. It is indifferent that the human eye can't have this color; in the first example it will appear like a gray dot, and in the second case it will definitely be a green eye.
completely control the image, do not let the optical tricks to ruin your design. It is OK if objects is not consistent from the technical point of view, but the entire picture must be flawless.
As an example, I pictured the packet of juice standing before me. The picture has plain color, gradients with broken lines, shadows and highlights and tints.
If I wrote about something bigger than icon design, this chapter wouldn't fit into an entire book, but the size of compositions restricts fonts too.
The resolution of symbols becomes the leading aspect as opposed to their look. Almost in any case, only if not the letters are the main part of the image, the text size has to be decreased to the greatest extent possible.
In general, almost any graphic studio has its unique font with small letters. Such a font can be created in several hours. You can browse the web and collect your own collection of very nice fonts. Primarily, I advice you to download the DS Pixel and Seventen 7Vedi website and the complete set of fonts from the Lakmus Lab website.
If you don't want a new font, tiny typesizes of Arial and Verdana may work. As a last option, you can draw the needed letters by hand.
There are quite a few rules there. First, letters cannot be less than 5 pixels high or less than 3 pixels wide.
Second, letters should not use anti-aliasing. It turns the font into an unrecognizable set of pixels.
Though, there are no rules without exceptions and the 5-point Arial appears perfectly readable.