Book Image

OpenLayers 3.x Cookbook - Second Edition

By : Peter J. Langley, Antonio Santiago Perez
Book Image

OpenLayers 3.x Cookbook - Second Edition

By: Peter J. Langley, Antonio Santiago Perez

Overview of this book

OpenLayers 3 is one of the most important and complete open source JavaScript mapping libraries today. Throughout this book, you will go through recipes that expose various features of OpenLayers 3, allowing you to gain an insight into building complex GIS web applications. You will get to grips with the basics of creating a map with common functionality and quickly advance to more complicated solutions that address modern challenges. You will explore into maps, raster and vector layers, and styling in depth. This book also includes problem solving and how-to recipes for the most common and important tasks.

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OpenLayers 3.x Cookbook - Second Edition
Peter J. Langley | Antonio Santiago Perez
Mar, 2016 | 304 pages
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Table of Contents (14 chapters)
OpenLayers 3.x Cookbook Second Edition
OpenLayers 3.x Cookbook Second Edition
Credits
Credits
About the Authors
About the Authors
About the Reviewer
About the Reviewer
www.PacktPub.com
www.PacktPub.com
Preface
Preface
Free Chapter
1
Web Mapping Basics
Web Mapping Basics
Introduction
Creating a simple fullscreen map
Playing with the map's options
Managing the map's stack layers
Managing the map's controls
Moving around the map view
Restricting the map's extent
2
Adding Raster Layers
Adding Raster Layers
Introduction
Using Bing imagery
Using OpenStreetMap imagery
Adding WMS layers
Changing the zoom effect
Changing layer opacity
Buffering the layer data to improve map navigation
Creating an image layer
Setting the tile size in WMS layers
3
Working with Vector Layers
Working with Vector Layers
Introduction
Adding a GML layer
Adding a KML layer
Creating features programmatically
Exporting features as GeoJSON
Reading and creating features from a WKT
Using point features as markers
Removing or cloning features using overlays
Zooming to the extent of a layer
Adding text labels to geometry points
Adding features from a WFS server
Using the cluster strategy
Reading features directly using AJAX
Creating a heat map
4
Working with Events
Working with Events
Introduction
Creating a side-by-side map comparator
Implementing a work-in-progress indicator for map layers
Listening for the vector layer features' events
Listening for mouse or touch events
Using the keyboard to pan or zoom
5
Adding Controls
Adding Controls
Introduction
Adding and removing controls
Working with geolocation
Placing controls outside the map
Drawing features across multiple vector layers
Modifying features
Measuring distances and areas
Getting feature information from a data source
Getting information from a WMS server
6
Styling Features
Styling Features
Introduction
Styling layers
Styling features based on geometry type
Styling based on feature attributes
Styling interaction render intents
Styling clustered features
7
Beyond the Basics
Beyond the Basics
Introduction
Working with projections
Creating a custom control
Selecting features by dragging out a selection area
Transitioning between weather forecast imagery
Using the custom OpenLayers library build
Drawing in freehand mode
Modifying layer appearance
Adding features to the vector layer by dragging and dropping them
Making use of map permalinks
Index
Index

Changing layer opacity

When you are working with many layers, both raster and vector layers, you will probably find situations where a layer that is on top of another layer obscures the one below it. This is more common when working with raster WMS layers without the transparent property set to true or tiled layers, such as OpenStreetMaps, and Bing Maps.

In this recipe, we'll create a slider that updates the layer opacity of the topmost layer, revealing a layer underneath as the opacity is lowered. The source code can be found in ch02/ch02-layer-opacity/. Here's a screenshot showing the layer opacity at 60%:

How to do it…

We used jQuery UI to create the slider widget. Here are the steps to create this recipe:

  1. Create an HTML file adding the required OpenLayers dependencies, as well as jQuery UI and dependencies. In particular, here's the markup for the map and opacity panels:

    <div id="js-map" class="map"></div>
<div class="pane">
  <h1>Layer opacity</h1>
  <p id...
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