手机刮刮乐HTML5代码, 使用原型prototype扩展了一个clearArc 清除圆内像素的功能， 此功能未完成扇形清除功能， 此外，在清除圆内的像素时，还有点瑕疵，右边和下边还不够圆滑，有明显的齿状。如果你找到修复方法请一定要告诉我哟。不过此清除方法用于刮刮乐已经完全满足需求了
代码语言：javascript复制<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>刮刮乐</title>
<script type="text/javascript">
window.onload = function() {
init();
}
CanvasRenderingContext2D.prototype.clearArc=function(x,y,radius,startAngle, endAngle, counterclockwise){
var distance = function(x0,y0,x1,y1){
var dis = Math.sqrt(Math.pow(x0-x1,2) Math.pow(y0-y1,2));
//return Math.ceil(dis10000)/10000;
return Math.round(dis10000)/10000;
};
//首先获得矩形
var diameter = radius2;
var startX = x-radius;
var cx = radius-(0-startX);
startX = startX<0?0:startX;
cx = cx-startX;
var startY = y-radius;
var cy = radius-(0-startY);
startY = startY<0?0:startY;
cy = cy-startY;
var imgData = this.getImageData(startX,startY,diameter,diameter);//需要处理的矩形
for (var i=0;i<imgData.data.length;i =4){
//矩阵内的坐标
var ii = i/4;
var ix = Math.floor(ii/imgData.width);
var iy = ii%imgData.height;
var dis = distance(ix,iy,cx,cy);
if(dis<=radius){//此点在圆内
imgData.data[i 0]=0;
imgData.data[i 1]=0;
imgData.data[i 2]=0;
imgData.data[i 3]=0;
continue;
}
var dr = dis-radius;
if(dr<Math.SQRT2){
var n = Math.sqrt(Math.pow(dr, 2)/2)256;//新
var o = imgData.data[i 3];
imgData.data[i 3]=n<o?n:o;
continue;
}
}
this.putImageData(imgData,startX,startY);
};
function init() {
var imageWidth = 200;
var imageHeight = 100;
var gglc = document.getElementById("gglc");
var gglc2D = gglc.getContext("2d");
gglc2D.fillStyle = '#cccccc'; //设置覆盖层的颜色
gglc2D.fillRect(1, 1, imageWidth, imageHeight); //设置覆盖的区域
//gglc2D.clearArc(25,25,20);
gglc.addEventListener("touchmove", function(event) {
event.preventDefault();
for(var i in event.targetTouches){
var touch = event.targetTouches[i];
gglc2D.clearArc(touch.pageX,touch.pageY,20);
}
}, false);
gglc.addEventListener("touchstart", function(event) {
event.preventDefault();
for(var i in event.targetTouches){
var touch = event.targetTouches[i];
gglc2D.clearArc(touch.pageX,touch.pageY,20);
}
}, false);
}
</script>
</head>
<body>
<div style="position: relative; width: 100%;height: 100%;">
<div style="position: absolute; width: 200px; height: 100px; text-align: center;line-height: 100px;border: 1px solid #ccc;'">谢谢惠顾</div>
<canvas style="position: absolute;" id="gglc" width="201" height="101"></canvas>
</div>
</body>
</html>
</pre> 
