testDetectChineseTofu.html
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	• bzimport
	Nov 22 2014, 3:04 AM

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testDetectChineseTofu.html
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	<!DOCTYPE html>
	<html>

	<head>
	<meta charset="utf-8"/>

	<script type="text/javascript">

	/**
	* Convert a Chinese Hanzi character to image data
	*
	* Draw the character on canvas, and return the bitmap in format: rgba rgba ...
	*
	* @param {string} character
	* @return {array}
	*/
	function convertHanziToImageData( character ) {
	var canv = document.createElement("canvas");
	canv.width = 80; // 4+72+4, put the 72px char at center, and leave 4px as padding
	canv.height= 80;

	var ctx=canv.getContext("2d");
	ctx.font="72px 宋体";
	ctx.fillText(character,4,68);

	var imgData=ctx.getImageData( 0, 0, canv.width, canv.height ).data;
	return imgData;
	}

	/**
	* Detect Chinese tofu
	*
	* Create tofu's and the character's images, compare them to see if the
	* character is rendered as a tofu
	*
	* @param {string} text
	* @return {boolean}
	*/
	function detectChineseTofu( character ) {
	// TODO: TOFU_IMAGE_DATA can be created only once
	var TOFU_IMAGE_DATA = convertHanziToImageData("鿿"); // a known tofu: 鿿

	var characterImageData = convertHanziToImageData( character );
	for (var i=0; i<TOFU_IMAGE_DATA.length; i++)
	if( characterImageData[i]!=TOFU_IMAGE_DATA[i] )
	return false;
	return true;
	}
	</script>
	</head>

	<body>

	<img id="canvasImg" src="" />

	<script>
	function testDetectChineseTofu( character ) {
	if( detectChineseTofu(character) )
	alert( character+" is tofu");
	else
	alert( character+" is not tofu");
	}

	testDetectChineseTofu("我");
	testDetectChineseTofu("鿾"); // another known tofu: 鿾

	</script>

	</body>
	</html>