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[转载]刮刮奖效果的简单实现 – ms_config – 博客园.
无意中看到个刮刮奖的效果,觉得很有意思.就想自己也做一个,怎样用html5及JavaScript实现呢,回忆以前
做报表的时候,用过html5 canvas元素.心里就有思路了.
惯例先用关键字在网上搜索了下,发现一些例子,已经做得很不错了,完全可以拿来主义.嘿…
自己简单改了下,就发布在runjs上去了.
源码如下:
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8" />
<title>eraser effect</title>
</head>
<body>
<div id="canvas"></div>
</body>
</html>
js
(function() {
// Creates a new canvas element and appends it as a child
// to the parent element, and returns the reference to
// the newly created canvas elemen
function createCanvas(parent, width, height) {
var canvas = {};
canvas.node = document.createElement('canvas');
canvas.context = canvas.node.getContext('2d');
canvas.node.width = width || 100;
canvas.node.height = height || 100;
parent.appendChild(canvas.node);
return canvas;
}
function init(container, width, height, fillColor) {
var canvas = createCanvas(container, width, height);
var ctx = canvas.context;
// define a custom fillCircle method
ctx.fillCircle = function(x, y, radius, fillColor) {
this.fillStyle = fillColor;
this.beginPath();
this.moveTo(x, y);
this.arc(x, y, radius, 0, Math.PI * 2, false);
this.fill();
};
ctx.clearTo = function(fillColor) {
ctx.fillStyle = fillColor;
ctx.fillRect(0, 0, width, height);
};
ctx.clearTo(fillColor || "#ddd");
// bind mouse events
canvas.node.onmousemove = function(e) {
if (!canvas.isDrawing) {
return;
}
var x = e.pageX - this.offsetLeft;
var y = e.pageY - this.offsetTop;
var radius = 10; // or whatever
var fillColor = '#ff0000';
ctx.globalCompositeOperation = 'destination-out';
ctx.fillCircle(x, y, radius, fillColor);
};
canvas.node.onmousedown = function(e) {
canvas.isDrawing = true;
};
canvas.node.onmouseup = function(e) {
canvas.isDrawing = false;
};
}
var container = document.getElementById('canvas');
init(container, 531, 438, '#ddd');
})();
#canvas {
background:url(http://www.topscratchcards.com/images/games/888ladies/scratchcard-winning-ticket.jpg);
width: 531px;
height: 438px;
}
