In this chapter we will cover the following topics:
Once we know how to work with vector layers, such as adding new features or modifying existing ones, the question that we may have in mind is: how do we style them? We have seen examples of feature styling in previous recipes in this book, but this chapter will take a deeper look into what we can do with styles and how styling operates in OpenLayers.
The visual representation of features is one of the most important concepts in GIS applications. It is not only important from the user's experience or the designer's perspective, but it is also important as an information requirement, for example, to identify features that match certain conditions.
The way that we visualize features is not only important to make our application much more attractive, but it is also important to improve the way that we bring information to the user. For example, assuming that a set of points represent some temperatures, if we are interested in the hottest zones, we could represent them with different radius and color values. This way, a lesser radius and a color near to blue would mean that the zone is a cold zone, while a greater radius and a color near to red would mean a hot zone.
OpenLayers offers us a great degree of flexibility when styling features. We can use static styles or dynamic styles that are influenced by feature attributes. Styles can be created through various methods, such as from style functions (ol.style.StyleFunction), or by applying new style instances (ol.style.Style) directly to a feature or layer.
Let's take a look at all of this in the following recipes.