Book Image

Mastering OpenLayers 3

By : Gábor Farkas
Book Image

Mastering OpenLayers 3

By: Gábor Farkas

Overview of this book

OpenLayers 3 allows you to create stunning web mapping and WebGIS applications. It uses modern, cutting edge browser technologies. It is written with Closure Library, enabling you to build browser-independent applications without painful debugging ceremonies, which even have some limited fallback options for older browsers. With this guide, you will be introduced to the world of advanced web mapping and WebGIS. First, you will be introduced to the advanced features and functionalities available in OpenLayers 3. Next, you will be taken through the key points of creating custom applications with OpenLayers 3. You will then learn how to create the web mapping application of yours (or your company's) dream with this open source, expense-free, yet very powerful library. We’ll also show you how to make amazing looking thematic maps and create great effects with canvas manipulation. By the end of this book, you will have a strong command of web mapping and will be well on your way to creating amazing applications using OpenLayers 3.
Table of Contents (17 chapters)
Mastering OpenLayers 3
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Creating a raster calculator


Now that we are familiar with some of the most useful canvas manipulation methods, let's take a look at a renderer that is independent of any image manipulation. There is a very useful source object in the library that can take multiple sources as input and create a new image based on the provided operations. In this example, called ch07_rastcalc, we will use the ol.source.Raster class to build a basic RasterCalculator function.

Raster 101

To understand the limitations of raster manipulation in OpenLayers 3 or, basically, any web mapping application, we should discuss how rasters work in GIS. If you are familiar with the concept, you can skip this part. If not, this section can give you some basic, but valuable, information, which can help you evaluate better architectural patterns.

First of all, every raster can be translated to a simple matrix. Rasters have a resolution and consist of uniform cells. Therefore, if we know the resolution of a raster, we can handle...