Let's discuss strictly technical aspects of icon creation
1. Lines, angles
One of the most important elements of the image is the outline of the object, i.e. rough line, which separates the object from the rest of the image. When creating normal-sized images, the artist rarely thinks about highlighting of objects with complementary lines. This is unnecessary because of the size: even non-contrasted objects do not blur into a single whole. Icon graphics is other story. Two variants are possible: either object and background colors have to be from opposite sides of the color wheel, or the object should be separated from the background by contrast outlines and shadows. I would like to discuss lines in more detail.
If we think more to the large scale images, we can note that in order to define contours, we can use all (including the most complicated) angles, Bezier splines and edges. In any case, the line will look ideal due to anti-aliasing. When decreasing the image scale to the small icon size, situation changes greatly. When every single pixel is equally valuable and can ruin the overall look of the composition, anti-aliasing is just not applicable. It means that you have to consider the possible line slopes.
The slope you choose for the line, specifies the step of this line. This means that every line is made of basic elements, the union of which defines its neatness and visual appeal.
For example, a 18-degree slope contains many small 3-pixel lines connected using a 1-pixel downshift:
This is how almost every line looks like. Primary element with joining followed by another primary element. However, not every angle creates lines that look look attractive and not messy.
For example, look at 25 and 20-degree angles:
It can be easily known which line is more appealing. The 25-degree slope produses a line consisting of even 2-pixel basic elements. The 20-degree slope has a basic element consisting of three lines: 3-pixel, 3-pixel and 2-pixel. The slope is more complex, thus, when not combined by other visual effects, it creates a feeling of untidiness: the basic elements have contrast which is too obvious to escape the human sight.
Here we can come to the first conclusion. The most "appropriate" angles have to make as simple basic elements as they can. therefore, the perfect slopes are 0 and 90 degrees. In those, 1-pixel basic elements are joined without downshift and form smooth lines. Less ideal are slopes which form primary elements of 1, 2, 3 pixel with 1-pixel downshift. Of course, the lines will not be smooth, but the human brain will process the picture and provide to the user what you intended to show to him. Also, the mentioned slopes can be considered acceptable (but at a stretch): slopes with primary elements consisting of unequal lines shifted by more than 1 pixel.
Now we can discuss 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 great amount of them is combined, 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 clearly seen that the line loses its solidness. It is not a single line anymore; it is a set of different lines, situated near one another. Rarely any artist wants its composition to look inconsistent. So, we come to another rule: if you use small angles, which produse long basic elements, it must be reasoned and employed with great attention.
And, finally, the third aspect I wanted to mention about lines. I already wrote that the primary element has to be as plain as possible.
For instance, a 25-degree angle can be produced in the two (of course more of them are possible) following ways:
In the first case the basic element is a 2-pixel line. In the other case, it consists of three elements: 3-pixel, 2-pixel and 1-pixel. The same slope but the image is different. The complex primary element made the line untidy.
Such examples can be produced for almost any angle, so in your works, make sure to simplify everything.
It can be said without an overstatement that the color is the main aspect of your work; improper or poorly balanced colors can kill even the best idea. What can we say about the color in icon graphics?
First, there is a clear rule: if the picture looks bad when reduced to grayscale, it means the colors that were selected are incorrect. This rule is true not only for icons but for the whole graphic design.
Second, you will be unable to apply common RGB. Sure, you may select GIF 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 consistently colored areas without blurring and jumps your project has, the more clear it looks. Pictograms are too small and the excess usage of complex filters makes the image look dirty.
Fourth, gradients. This is a wonderful instrument which can improve the look of any project. Besides esthetics, gradients are an ideal way to get rid of the "broken line" look (lines with too long primary elements). But be careful when using them since too many gradients can kill the plain color, and be unable to fit into the gif palette.
Fifth, shadows and flares. All rules for using shades and flares in icon design are totally the same to the rules of the overall graphic design. The only thing I would like to note: draw everything by hand. Don't use filters, make all shades and flares in a different layer and then edit its transparency. If using effects, you rarely can predict what will it look like. It is unfavorable when you don't control the making of a project. It is awful if you can't control it if drawing icons.
And, finally, sixth. Nuancing is the main aspect of pictogram design, which greatly affects the esthetic appearance of the image. When the blue human eye in the image has the size of 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 such color; in the first case it will appear like a gray dot, but in the second example it will definitely be a green eye.
completely control the picture, do not allow the visual tricks to ruin your work. It is OK if objects is not consistent from the technical point of view, but the entire image must be flawless.
As an example, I pictured the packet of juice located in front of me. The image has plain color, gradients with broken lines, shadows and highlights and tints.
If I wrote about something bigger than miniature creation, this part wouldn't fit into an entire book, but the size of images ;limits fonts too.
The size of symbols becomes the leading aspect as opposed to their beauty. Nearly in any case, unless the letters are the main part of the image, the font size has to be reduced to the largest extent possible.
In general, almost any graphic studio has its own font with tiny letters. Such a font can be made in a few hours. You can search the internet and make your own collection of very nice fonts. Primarily, I would recommend you to download the DS Pixel and Seventen 7Vedi website and the whole set of fonts from the Lakmus Lab website.
If you don't want a new font, small sizes of Arial and Verdana will work. As a last resort, you can create the necessary characters by hand.
There are quite a few 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 transforms the font into an incomprehensible set of pixels.
Though, there are no rules without exceptions and the 5-point Arial appears rather readable.