html5 canvas自定义圆角矩形与虚线(roundedrectangle and dash line)

实现向HTML Canvas 2d context绘制对象中添加自定义的函数功能演示，如何绘制虚线

以及控制虚线间隔大小，学会绘制圆角矩形的技巧。

HTML5 Canvas绘制对象中提供的原生功能没有实现绘制圆角矩形与虚线的功能，但是

通过JavaScript语言的Object.prototype可以实现对对象CanvasRenderingContext2D添

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加这两个函数功能。代码的演示效果如下：

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组件fishcomponent.js的代码如下：

CanvasRenderingContext2D.prototype.roundRect =
	function(x, y, width, height, radius, fill, stroke) {
		if (typeof stroke == "undefined") {
			stroke = true;
		}
		if (typeof radius === "undefined") {
			radius = 5;
		}
		this.beginPath();
		this.moveTo(x + radius, y);
		this.lineTo(x + width - radius, y);
		this.quadraticCurveTo(x + width, y, x + width, y + radius);
		this.lineTo(x + width, y + height - radius);
		this.quadraticCurveTo(x + width, y + height, x + width - radius, y+ height);
		this.lineTo(x + radius, y + height);
		this.quadraticCurveTo(x, y + height, x, y + height - radius);
		this.lineTo(x, y + radius);
		this.quadraticCurveTo(x, y, x + radius, y);
		this.closePath();
		if (stroke) {
			this.stroke();
		}
		if (fill) {
			this.fill();
		}
};

CanvasRenderingContext2D.prototype.dashedLineTo = function (fromX, fromY, toX, toY, pattern) {
	// default interval distance -> 5px
	if (typeof pattern === "undefined") {
		pattern = 5;
	}

	// calculate the delta x and delta y
	var dx = (toX - fromX);
	var dy = (toY - fromY);
	var distance = Math.floor(Math.sqrt(dx*dx + dy*dy));
	var dashlineInteveral = (pattern <= 0) ? distance : (distance/pattern);
	var deltay = (dy/distance) * pattern;
	var deltax = (dx/distance) * pattern;
	
	// draw dash line
	this.beginPath();
	for(var dl=0; dl
HTML中调用演示：








	


	
HTML5 Canvas Dash-line Demo - By Gloomy Fish
	
Dash line and Rounded Rectangle