Canvas Shear Transform Using HTML 5

Deepak Dwij
May 19, 2012
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Introduction

In this article we are going to understand the concept of Canvas Shear Transform Using HTML 5. In this section to shear the HTML5 canvas, we can use the transform() method with the transformation matrix below. The horizontal shear is defined by sx and the vertical shear is defined by sy.

Shear matrix.

1 sx 0
sy 1 0
0 0 1

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

Let's see how the CanvasShearTransforms 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 sheartransform.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;
}
#myCanvas
{
   border: 2px solid #FFFFCC;
   margin-top: 50px;
   margin-left: 50px;
   background-color: #CCCCCC;
   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 understanding how the JavaScript works, download the attached .rar file and run the CanvasShearTransforms application.

The whole JavaScript looks as in the following.

<script>
        window.onload = function ()
        {
            var canvas = document.getElementById("myCanvas");
            var context = canvas.getContext("2d");
            var rectWidth = 150;
            var rectHeight = 75;
            var sx = 0.75;
            var sy = 0;
            context.translate(canvas.width / 2, canvas.height / 2);
            // apply custom transform
            context.transform(1, sy, sx, 1, 0, 0);
            context.fillStyle = "red";
            context.fillRect(-rectWidth / 2, -rectHeight / 2, rectWidth, rectHeight);
        };
</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 sheartransform.aspx page. Here we pass a Canvas in the canvas tag:

<body style="background-color: #FFCCCC">
    <center>
        <h1>
            Canvas Shear Transform
        </h1>
    </center>
    <hr />
    <canvas id="myCanvas" width="540" height="200">
        </canvas>
</body>

Step 5 : The complete code for the CanvasShearTransforms application is:

<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="sheartransform.aspx.cs" Inherits="CanvasShearTransforms._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: #FFCCCC">
    <center>
        <h1>
            Canvas Shear Transform
        </h1>
    </center>
    <hr />
    <canvas id="myCanvas" width="540" 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. You will see the shear the HTML5 canvas while displaying in the browser.

Here are the some useful resources.

Canvas Anchor Points Using HTML 5
Canvas Shape Layering Using HTML 5
Canvas Clipping Region Using HTML 5
Use Canvas Tag in HTML 5
Curve Detection With Canvas Using HTML 5