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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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

Setting the tile size in WMS layers

Setting a custom tile size for a WMS layer in OpenLayers 3 is a bit more involved than with OpenLayers 2. It requires the use of the ol.tilegrid.TileGrid class. This class provides some flexible control over the grid pattern that is used for sources accessing tiled image servers.

Of course, controlling the tile size of the WMS request can affect the performance. By default, the tile size is 256 x 256 pixels, but we can set this to something different. Bigger tile sizes mean fewer requests to the server but more computation time to generate a bigger image and a larger download size per image. On the contrary, smaller tile sizes mean more server requests and less time to compute smaller images. If you use the default tile sizes, then it's more likely the images will have already been cached, so it may increase performance.

In any case, it's good to know how we can make these adjustments. The source code can be found in ch02/ch02-tile-size/. Here's what we...

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