Let's discuss strictly technical details of icon creation
1. Lines, angles
One of the most important parts of the image is the framework of the object, i.e. solid border, which limits the object from the rest of the image. When designing large-scale graphics, the artist rarely cares about highlighting of objects with additional outlines. This is not needed because of the scale: even low contrast objects do not blend into a one. Icon graphics is different. Two solutions are possible: either foreground 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 would like to dwell on lines in more detail.
If we return more to the large scale images, we see that in order to highlight edges, we can use any (even the most complex) angles, Bezier splines and borders. Anyway, the line will look ideal due to anti-aliasing. When shrinking the image dimensions to the size of an icon, situation changes dramatically. When each particular pixel is vitally important and can ruin the overall appearance of the composition, anti-aliasing is simply unreasonable. It means that you have to consider the possible line angles.
The slope you select for the line, determines the step of this line. This means that every line is made of basic elements, the combination of which defines its accuracy and visual appeal.
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. Basic element followed by joining followed by another basic element. However, not every slope creates lines that look look attractive and not annoying.
For example, look at 25 and 20-degree slopes:
It can be easily known which line is more attractive. The 25-degree angle makes a line containing even 2-pixel primary elements. The 20-degree angle has a primary element consisting of three parts: 3-pixel, 3-pixel and 2-pixel. The angle is more complicated, therefore, if not combined by additional visual effects, it creates a feeling of untidiness: the basic elements have contrast which is too strong 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 angles are 0 and 90 degrees. In them, 1-pixel basic elements are combined without downshift and form smooth lines. Less ideal are slopes which form basic elements of 1, 2, 3 pixel with 1-pixel downshift. Of course, the lines will not be even, but the human sight will process the image and present to the user what you meant to show to him. Also, the following slopes can be considered acceptable (but at a stretch): slopes with primary elements made of different lines shifted by more than 1 pixel.
Now we can discuss another problem. In the previous paragraph, I purposely defined slopes with basic elements of 1, 2 and 3 pixels as correct. Such tiny lines, especially when a large amount of them is joined, appear as a single whole. But what do we see if we increase the basic elements to 10 or 20 pixels?
Here is an example:
It can be obviously noticed that the line loses its integrity. It is not a continuous line anymore; it is a combination of different lines, situated near each other. Hardly any designer wants its creation to look that way. So, we have another conclusion: if you use small angles, which make long basic elements, it has to be reasoned and used with maximum attention.
And, finally, the last thing I wanted to mention about lines. I already wrote that the basic element has to be as simple as possible.
For example, a 25-degree slope can be drawn in the two (sure more of them exists) following ways:
In the first picture the basic element is a 2-pixel line. In the other case, it is made of three elements: 3-pixel, 2-pixel and 1-pixel. The same slope but the look is different. The complicated basic element made the line untidy.
This examples can be produced for almost any slope, so in your works, make sure to simplify everything.
It can be said without an exaggeration that the color is the leading aspect of your work; improper or poorly balanced colors can kill even the best idea. What can we write about the color in icon graphics?
First, there is a certain rule: if the image looks poor when reduced to monochrome, then the colors that were chosen are wrong. This rule is valid not only for icons but for the whole graphic design.
Second, you will probably unable to apply safe RGB. Of course, you may select GIF colors only, but this ties you hand and foot. Gradients, shadows, blending and many other tricks will not be available to you.
Third, try to increase the areas of "plain" color. The more consistently colored parts without blurring and jumps your picture has, the more neat it appears. Pictograms are too tiny and the over usage of complex effects makes the picture look messy.
Fourth, gradients. This is a great tool which can improve the appearance of any project. Besides visuals, gradients are a perfect way to get rid of the "broken line" look (lines with too long primary elements). But be careful when applying them since too many gradients can kill the plain color, and be unable to fit into the gif palette.
Fifth, shadows and highlights. All aspects of applying shades and flares in icon creation are completely the same to the rules of the general graphic design. The only thing I would like to mention: create everything yourself. Don't apply filters, make all shades and flares in a separate layer and then edit its transparency. If using filters, you rarely know what the result will be. It is unfavorable when you don't control the making of a project. It is worse if you can't control it when drawing icons.
And, lastly, sixth. Tinting is the key detail of pictogram creation, which largely affects the esthetic appearance of the image. If the blue human eye in the image has the size of 1 pixel, increase the color intensiveness. For instance, instead of 0, 131, 159 make 71, 195, 242. It is indifferent that the human eye never has such color; in the first example it will look like a gray dot, but in the second one it will really be a green eye.
Thoroughly control the picture, do not allow the visual illusions to spoil your design. It is acceptable if something is not consistent from the technical point of view, but the whole picture must be flawless.
As an example, I pictured the pack of juice standing before me. The picture has plain color, gradients with broken lines, shades and highlights and tints.
If I talked about something other than pictogram creation, this chapter wouldn't fit into an entire book, but the size of images ;limits fonts too.
The resolution of symbols is the main issue as opposed to their look. Almost in all cases, only if not the letters are the main part of the project, the text size must be decreased to the greatest extent possible.
In general, virtually any graphic studio has its unique font with small characters. Such a font can be created in a couple of hours. You can browse the web and collect your own library of very interesting fonts. First of all, I advice you to download the DS Pixel and Seventen 7Vedi webpage and the entire set of fonts from the Lakmus Lab website.
If you don't want a new font, little typesizes of Arial and Verdana may work. As a last resort, you can draw the needed 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 turns the text into an incomprehensible set of pixels.
Though, there are no rules without exceptions and the 5-point Arial looks perfectly readable.