Book Image

OpenLayers Cookbook

Book Image

OpenLayers Cookbook

Overview of this book

Data visualization and analysis has become an important task for many companies. Understanding the basic concepts of GIS and knowing how to visualize data on a map is a required ability for many professionals today. OpenLayers is a JavaScript library to load, display, and render maps from multiple sources on web pages."OpenLayers Cookbook" teaches how to work with OpenLayers, one of the most important and complete open source JavaScript libraries.Through an extensive set of recipes, this book shows how to work with the main concepts required to build a GIS web applicationñ maps, raster and vector layers, styling, theming, and so on."OpenLayers Cookbook" includes problem solving and how-to recipes for the most common and important tasks. A wide range of topics are covered.The range of recipes includes: creating basic maps, working with raster and vector layers, understanding events and working with main controls, reading features from different data sources, styling features, and understanding the underlying architecture."OpenLayers Cookbook" describes solutions and optimizations to problems commonly found.
Table of Contents (15 chapters)
OpenLayers Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

Understanding how themes work using the theme folder


As we have explained in the chapter's introduction, there are some OpenLayers controls strongly based on CSS classes to be the theme.

In this group, we can find the PanPanel control, a small control formed by a set of four buttons that allows the user to pan the map in four directions:

How to do it...

  1. Create an HTML page and add the OpenLayers ibrary dependencies:

    <script type="text/javascript" src="./js/OpenLayers-2.11/lib/OpenLayers.js"></script> 
  2. After this, we need to include the CSS file with the theme to be used. Here we are using the default theme:

    <link rel="stylesheet" href="./js/OpenLayers-2.11/theme/default/style.css" type="text/css">
  3. Within the body element of the document, add the div element to hold the map:

    <div id="ch06_theming_theme" style="width: 100%; height: 90%;"></div>
  4. Within a script element, add the code to create the map with a base layer:

        var map = new OpenLayers.Map("ch06_theming_img...