Canvas Planet Image Map Using HTML 5

Deepak Dwij
Mar 22, 2012
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Introduction

In this article we are going to understand the concept of a canvas planet image map using HTML 5. In this section you will see, with the mouse over the planets, the names of the planets and use of a check box to show and hide the map overlay while running the application in the browser.

Here we will use some JavaScript and some styles along with HTML code. Just go through the steps to see how to create this application.

Let's see how the PlanetImageMap application can be created. To do so use the following steps.

Step 1 : Open a HTML editor or Visual Studio.

Open File menu ->select new ->Choose Website then.

This is where we will create the HTML5 application.

Go to Solution Explorer
Right-click on the Application name
Select Add-->add new item
Now in the window that opens, select an HTML page or new Web form
Rename it to canvasplanetimage.aspx

Step 2 : In this section we will create the style for the media and create the .css on the media screen. Put the given script in the Head section of the HTML or between the <head>--</head> tags. Here the CSS is used for design purposes.

CSS Script

<style>
        body
        {
            margin: 0px;
           padding: 0px;
            font-family: Calibri;
        }
        canvas
        {
            border: 1px solid #9C9898;
            margin-left: 15px;
        }
        #page
        {
            position: relative;
            width: 580px;
            height: 253px;
        }
        #controls
        {
            position: absolute;
            right: 10px;
            top: 10px;
            z-index: 99999;
        }
        label
        {
            color: white;
            vertical-align: top;
        }
</style>

Step 3 : In this part we need to work on some JavaScript. To fully understand how JavaScript works, download the attached .rar file and run the PlanetImageMap application.

The whole JavaScript looks as in the following

window.onload = function ()
   {
            var stage = new Kinetic.Stage("container", 578, 251);
            var planetsLayer = new Kinetic.Layer();
            var circlesLayer = new Kinetic.Layer();
            var messageLayer = new Kinetic.Layer();
            var planets = {
                Mercury: {
                    x: 46,
                    y: 126,
                    radius: 32
                },
                Venus: {
                    x: 179,
                    y: 126,
                    radius: 79
                },
                Earth: {
                    x: 366,
                    y: 127,
                    radius: 85
                },
                Mars: {
                    x: 515,
                    y: 127,
                    radius: 45
                }
            };
            var imageObj = new Image();
            imageObj.onload = function ()
               {
                // draw shape overlays
                for (var pubKey in planets)
                 {
                    (function () {
                        var key = pubKey;
                        var planet = planets[key];
                        var planetOverlay = new Kinetic.Shape({
                        drawFunc: function () {
                        var context = this.getContext();
                        context.beginPath();
                        context.arc(planet.x, planet.y, planet.radius, 0, Math.PI * 2, false);
                        context.closePath();
                        if (this.show) {
                        context.fillStyle = "red";
                        context.fill();
                         }
                       },
                      // custom property
                       show: false
                   });
                         planetOverlay.on("mouseover", function ()
                        {
                            writeMessage(messageLayer, key);
                        });
                        planetOverlay.on("mouseout", function ()
                        {
                            writeMessage(messageLayer, "");
                        });
                        circlesLayer.add(planetOverlay);
                  } ());
     }

Step 4 : In this section we are going to become familiar with the body part of HTML scripting. Replace this script from the body section of the canvasplanetimage.aspx page. Here we pass a Canvas in the canvas tag.

<body style="background-color: #FFFFCC">
    <center>
        <h2>
            Canvas Planet Image Map
        </h2>
    </center>
    <hr />
    <div id="page">
        <div id="container">
        </div>
        <div id="controls">
            <input type="checkbox" id="checkbox">
            <label>
                Show map overlay
            </label>
        </div>
    </div>
</body>

Step 5 : The complete code for the PlanetImageMap application:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="canvasplanetimage.aspx.cs" Inherits="PlanetImageMap.canvasplanetimage" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
    <script src="jscript.js">
    </script>
    <script>
    </script>
</head>
<body style="background-color: #FFFFCC">
    <center>
        <h2>
            Canvas Planet Image Map
        </h2>
    </center>
    <hr />
    <div id="page">
        <div id="container">
        </div>
        <div id="controls">
            <input type="checkbox" id="checkbox">
            <label>
                Show map overlay
            </label>
        </div>
    </div>
</body>
</html>

Step 6 : Output Press F5

Note : For the accurate output of HTML5 applications, you must have the Google Chrome browser in your PC. You will see mouse over the planets to see their names and use the check box to show and hide the map overlay while running the application on the browser.

When you hover the mouse over the left hand side as shown in the following figure you will get the name as Mercury.

When you hover the mouse over the third to the left hand side as shown in the figure you will get the name as Earth.

When you press the check box you will get the overlay image.

Here are the some useful resources.

Canvas Anchor Points Using HTML 5
Canvas Oscillation Animation Using HTML 5
Canvas Mirror Transform Using HTML 5
Canvas Clipping Region Using HTML 5
Canvas Shape Layering Using HTML 5