Let's consider purely technical details of icon design
1. Lines, slopes
One of the vital elements of the image is the outline of the object, i.e. solid line, which separates the object from the rest of the image. When working with normal-sized graphics, the designer occasionally cares about highlighting of objects with complementary outlines. This is not needed because of the scale: even low contrast objects do not blur into a single whole. Icon graphics is different. Two solutions are possible: either object and background colors must be from opposite sides of the color chart, or the object must be separated from the background by contrast lines and shadows. I would like to discuss lines deeper.
If we return again to the large scale graphics, we see that in order to highlight edges, we can use all (even the most complicated) angles, Bezier splines and borders. In any case, the line will look ideal due to anti-aliasing. When decreasing the image scale to the size of an icon, situation changes dramatically. When every single pixel is vitally valuable and can change the overall look of the icon, anti-aliasing is simply not applicable. It comes that you should consider the possible line angles.
The slope you choose for the line, specifies the step of this line. This means that each line is made of primary elements, the union of which determines its neatness and esthetics.
For example, a 18-degree angle contains many small 3-pixel lines connected using a 1-pixel downshift:
This is how nearly each line looks like. Primary element followed by joining followed by second primary element. Unfortunately, not each angle creates lines that look look attractive and not annoying.
For example, look at 25 and 20-degree slopes:
It can be easily seen which line is more appealing. The 25-degree slope makes a line containing 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 slope is more complicated, thus, when not combined by other 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 come to the first conclusion. The most "correct" angles must make as simple basic elements as possible. therefore, the ideal angles are 0 and 90 degrees. In them, 1-pixel basic elements are combined without downshift and form smooth lines. Less perfect 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 brain will process the image and present to the viewer what you intended to show to him. Also, the mentioned angles can be considered correct (but at a stretch): slopes with primary elements consisting of unequal 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 correct. Such small lines, especially when a great number of them is combined, appear as solid. But what happens if we change the basic elements to 10 or 20 pixels?
Here is an example:
It can be obviously seen that the line loses its solidness. It is not a single line now; it is a combination of several lines, situated near each other. Hardly any designer wants its creation to look inconsistent. So, we come to another rule: if you use minimal angles, which produse long basic elements, it must be reasoned and used with great caution.
And, finally, the third aspect I wanted to tell about lines. I did write that the basic element should be as plain as it can.
For instance, a 25-degree slope can be produced in the two (of course more of them exists) following ways:
In the first picture the basic element is a 2-pixel line. In the second case, it is made of three elements: 3-pixel, 2-pixel and 1-pixel. The same angle but the image is different. The complex primary element made the line untidy.
This examples can be produced for about any slope, so in your works, make sure 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 balanced colors can kill even the best idea. What can we say about the color in miniature graphics?
First, there is a clear rule: if the image looks bad when converted to monochrome, it means the colors that were selected are wrong. This rule is true not exclusively for icons but for the whole graphic design.
Second, you will probably unable to use safe RGB. Of course, you can select GIF colors only, but this ties you hand and foot. Gradients, shadows, blending and many other tricks will not be accessible to you.
Third, try to enlarge the portion of "plain" color. The more evenly colored parts without diffusion and jumps your picture has, the more neat it appears. Pictograms are too small and the over usage of special filters makes the image look messy.
Fourth, gradients. This is a wonderful tool which can change the appearance of any picture. Besides visuals, gradients are a perfect way to get rid of the "broken line" look (lines with too long basic elements). But be careful when using them because too much gradients can kill the flat color, and be unable to fit into the gif palette.
Fifth, shadows and highlights. All rules for applying shades and highlights in icon making are totally identical to the rules of the overall graphic design. The only thing I would like to note: create everything yourself. Don't apply effects, make all shadows and highlights in a different layer and then edit its transparency. If applying effects, you rarely can predict what the result will be. It is unfavorable when you can't control the making of a composition. It is awful if you don't control it if creating miniatures.
And, lastly, sixth. Tinting is the main detail of pictogram creation, which greatly affects the visual appearance of the composition. If the green human eye in the icon is sized 1 pixel, increase the color saturation. For example, instead of 0, 131, 159 choose 71, 195, 242. It doesn't matter that the human eye never has this color; in the first example it will look like a gray dot, and in the second one it will really be a green eye.
Thoroughly control the image, do not allow the visual tricks to ruin your work. It is OK if something is not perfect technically, but the whole image must be flawless.
As an example, I pictured the pack of juice standing in front of me. The image has plain color, gradients with broken lines, shades and highlights and tints.
If I talked about something bigger than miniature creation, this part wouldn't fit into an entire book, but the resolution of pictures restricts fonts too.
The resolution of letters is the leading aspect as opposed to their beauty. Almost in any case, unless the letters are the main part of the composition, the text size must be reduced to the largest extent possible.
In principle, virtually any design company has its own font with tiny letters. This font can be crafted in a few hours. You can browse the internet and collect your own library of very nice fonts. First of all, I advice you to download the DS Pixel and Seventen 7Vedi website as well as the whole set of fonts from the Lakmus Lab website.
If you don't want a new font, tiny sizes of Arial and Verdana will work. As a last resort, you can create the necessary characters yourself.
There are not many 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 transforms the text into an unrecognizable mixture of pixels.
However, there are no rules without exceptions and the 5-point Arial looks rather understandable.