You are previewing Supercharged JavaScript Graphics.

Supercharged JavaScript Graphics

Cover of Supercharged JavaScript Graphics by Raffaele Cecco Published by O'Reilly Media, Inc.
  1. Supercharged JavaScript Graphics
    1. SPECIAL OFFER: Upgrade this ebook with O’Reilly
    2. Preface
      1. Audience and Assumptions
      2. Organization
      3. Conventions Used in This Book
      4. Using Code Examples
      5. Safari® Books Online
      6. How to Contact Us
      7. Acknowledgments
    3. 1. Code Reuse and Optimization
      1. Keeping It Fast
      2. What and When to Optimize
      3. Homespun Code Profiling
      4. Optimizing JavaScript
      5. Optimizing jQuery and DOM Interaction
      6. Other Resources
    4. 2. DHTML Essentials
      1. Creating DHTML Sprites
      2. Converting into a jQuery Plug-in
      3. Timers, Speed, and Frame Rate
      4. Internet Explorer 6 Background Image Caching
    5. 3. Scrolling
      1. CSS-Only Scrolling Effects
      2. Scrolling with JavaScript
    6. 4. Advanced UI
      1. HTML5 Forms
      2. Using JavaScript UI Libraries
      3. Creating UI Elements from Scratch
    7. 5. Introduction to JavaScript Games
      1. Game Objects Overview
      2. The Game Code
    8. 6. HTML5 Canvas
      1. Canvas Support
      2. Bitmaps, Vectors, or Both?
      3. Canvas Limitations
      4. Canvas Versus SVG
      5. Canvas Versus Adobe Flash
      6. Canvas Exporters
      7. Canvas Drawing Basics
      8. Animating with Canvas
      9. Canvas and Recursive Drawing
      10. Replacing DHTML Sprites with Canvas Sprites
      11. A Graphical Chat Application with Canvas and WebSockets
    9. 7. Vectors for Games and Simulations
      1. Operations on Vectors
      2. Creating a JavaScript Vector Object
      3. A Cannon Simulation Using Vectors
      4. Rocket Simulation
    10. 8. Google Visualizations
      1. Limitations
      2. Chart Glossary
      3. Image Charts
      4. Interactive Charts
    11. 9. Reaching the Small Screen with jQuery Mobile
      1. jQuery Mobile
      2. TilePic: A Mobile-Friendly Web Application
      3. PhoneGap
    12. 10. Creating Android Apps with PhoneGap
      1. Installing PhoneGap
      2. Creating a PhoneGap Project in Eclipse
    13. Index
    14. About the Author
    15. Colophon
    16. SPECIAL OFFER: Upgrade this ebook with O’Reilly

Scrolling with JavaScript

Although the CSS scrolling techniques described earlier can give some nice effects, the lack of control is frustrating: the parallax effects work only when the browser window is resized, so there is no guarantee that the user will even see the effect. However, with JavaScript, there are no limitations as to how and when scrolling effects can occur. In this section, we will examine two types of JavaScript scrolling techniques: background image scrolling and the more sophisticated tile-based image scrolling.

Background Image Scrolling

The following section recreates the CSS effect in Figure 3-3, but this time, the movement of the mouse over the page controls the direction and speed of scrolling via JavaScript. As the mouse moves to either the left or right of the page, the scrolling will accelerate in the same direction, slowing to a stop as the mouse moves into the middle of the page, or stopping completely when the mouse leaves the page altogether.

With the CSS scrolling code shown earlier in Example 3-1, the background image positions were specified as a percentage of the browser window size. In Example 3-2, the background image positions are manipulated as pixel positions.


For convenience, jQuery is used in the example code.

Example 3-2. Simple JavaScript scrolling

<!DOCTYPE html> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>CSS Parallax</title> <style type="text/css"> body { padding:0px; margin:0px; } .layer ...

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