Canvas Element Pattern: HTML5

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Today lets learn how to create pattern from another canvas element.

canvas-element-pattern-html5

In this video tutorial, we take 2 canvas elements. Draw a small circle on one canvas and use it as pattern and draw a bigger circle on the main canvas.

HTML file
index.html

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< !DOCTYPE HTML>
<html>
<head>
<title>Canvas: HTML5</title>
<meta charset="utf-8"/>
<link href="myStyle.css" rel="stylesheet" />
<script src="myScript.js"></script>
</head>
<body>
 <canvas id="myCanvas" width="400" height="400">
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 </canvas>
 
 <canvas id="pattern" width="50" height="50">
 	Please upgrade your browser!
 </canvas>
 
</body>
</html>

Here we have 2 canvas elements with unique ids. First/Main canvas is 400px X 400px width and height, second canvas is 50px X 50px width and height.
Related: Canvas Basics: HTML5

CSS file
myStyle.css

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canvas {
	border: 2px dotted black;
}

We assign 2px black dotted border to both the canvas present on our HTML page.

JavaScript file: Pattern Code
myScript.js

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		var pCanvas          = document.getElementById("pattern");	
		var pContext         = pCanvas.getContext("2d");
 
		pContext.lineWidth   = 2;
		pContext.arc(25, 25, 10, 0, 2 * Math.PI);
		pContext.strokeStyle = "red";
		pContext.fillStyle   = "blue";
		pContext.stroke();
		pContext.fill();

Here we get the pattern id and extract the 2d context APIs. Using pContext object, we draw a small circle of radius 10px with red border and filled with blue color.
Related: Draw Arcs/Circle with Canvas: HTML5

JavaScript file: Main Canvas Code
myScript.js

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		context.fillStyle    = context.createPattern(pCanvas, "repeat");
		context.strokeStyle  = "pink";
		context.arc(200, 200, 100, 0, 2 * Math.PI);
		context.stroke();
		context.fill();

We assign previously created pattern to fillStyle of our main canvas context. With this pattern as fillStyle, and a pink border, we draw a circle which has a radius of 100px.
Related: Canvas Image Patterns: HTML5

JavaScript file: Full Code
myScript.js

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window.onload = canvas;
 
function canvas()
{
	var myCanvas = document.getElementById("myCanvas");
 
	if( myCanvas && myCanvas.getContext("2d") ) 
	{
		var context            = myCanvas.getContext("2d");
 
		var pCanvas            = document.getElementById("pattern");	
		var pContext           = pCanvas.getContext("2d");
 
		pContext.lineWidth     = 2;
		pContext.arc(25, 25, 10, 0, 2 * Math.PI);
		pContext.strokeStyle   = "red";
		pContext.fillStyle     = "blue";
		pContext.stroke();
		pContext.fill();
 
		context.shadowColor    = "black";
		//context.shadowOffsetX= - 10;
		//context.shadowOffsetY= - 10;
		context.shadowBlur     = 10;
 
		context.fillStyle      = context.createPattern(pCanvas, "repeat");
		context.strokeStyle    = "pink";
		context.arc(200, 200, 100, 0, 2 * Math.PI);
		context.stroke();
		context.fill();
	}
}

We’re making the main canvas circle stand out by applying shadow effects.
Related: Shadow Effect on Canvas: HTML5

Canvas Element Pattern: HTML5


You need to a flashplayer enabled browser to view this YouTube video

YouTube Link: http://www.youtube.com/watch?v=2LuBWIzs_EY [Watch the Video In Full Screen.]



Patterns can be used creatively in HTML5 games development and to draw images which look like having a 2d or 3d dimensions.

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