Canvas Line Join Using HTML 5

Deepak Dwij
May 19, 2012
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Article

Introduction

In this article we are going to understand joining lines using a HTML 5 canvas. In this section, to set the line join style of an HTML5 Canvas path, we can use the lineJoin context property. Paths can have one of three line joins: miter, round, or bevel. Unless otherwise specified, the HTML5 Canvas line join property is defaulted with the miter style.

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 CanvasLineJoining 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

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 Default.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;
}
Canvas
{
   border: 2px solid #9C9898;
   margin-top: 50px;
   margin-left: 50px;
   background-color: #F4D19F;
   box-shadow: 5px 5px 8px #222;
}
.title
{
   text-align: center;
   font-family: Segoe UI Light, Arial, Helvetica;
   font-size: 2.2em;
   margin: 1em;
}
.info
{
   text-align: center;
   font-family: Segoe UI Light, Arial, Helvetica;
   font-size: 1.2em;
   margin: 0.25em;
}
</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 CanvasLineJoining application.

The whole JavaScript looks as in the following:

    <script>
            window.onload = function ()
            {
            var canvas = document.getElementById("myCanvas");
            var context = canvas.getContext("2d");
            // miter line joine (left)
            context.beginPath();
            context.moveTo(canvas.width / 2 - 50 - 140, canvas.height - 50); // line 1
            context.lineTo(canvas.width / 2 - 140, 50); // line 1
            context.lineTo(canvas.width / 2 + 50 - 140, canvas.height - 50); // line 1
            context.lineWidth = 25;
            context.lineJoin = "miter";
            context.stroke();
            // round line join (middle)
            context.beginPath();
            context.moveTo(canvas.width / 2 - 50, canvas.height - 50); // line 1
            context.lineTo(canvas.width / 2, 50); // line 1
            context.lineTo(canvas.width / 2 + 50, canvas.height - 50); // line 1
            context.lineWidth = 25;
            context.lineJoin = "round";
            context.stroke();
            // bevel line join (right)
            context.beginPath();
            context.moveTo(canvas.width / 2 - 50 + 140, canvas.height - 50); // line 1
            context.lineTo(canvas.width / 2 + 140, 50); // line 1
            context.lineTo(canvas.width / 2 + 50 + 140, canvas.height - 50); // line 1
            context.lineWidth = 25;
            context.lineJoin = "bevel";
            context.stroke();
        };
   </script>

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 Default.aspx page. Here we pass a Canvas in the canvas tag.

<body style="background-color: #C9E0E6">
    <center>
        <h1>
            Canvas Line Joining In HTML 5
        </h1>
    </center>
    <hr />
    <canvas id="myCanvas" width="578" height="200">
    </canvas>
</body>

Step 5 : The complete code for the CanvasLineJoining application.

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default.aspx.cs" Inherits="_Default" %>
<!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">
    <style>
    </style>
    <script>
    </script>
</head>
<body style="background-color: #C9E0E6">
    <center>
        <h1>
            Canvas Line Joining In HTML 5
        </h1>
    </center>
    <hr />
    <canvas id="myCanvas" width="578" height="200">
    </canvas>
</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. Here the Canvas line joining displays when the application runs on the browser.

Here are the some useful resources