jquery实现擦除效果

来源：互联网发布：数码宝贝网络侦探bgm 编辑：程序博客网时间：2024/05/16 15:33
效果展示：
代码实现：
<!DOCTYPE html><html><head><meta charset="UTF-8"><title>刮刮卡</title><!-- 新 Bootstrap 核心 CSS 文件 --><link rel="stylesheet" href="//cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap.min.css"><!-- 可选的Bootstrap主题文件（一般不用引入） --><link rel="stylesheet" href="//cdn.bootcss.com/bootstrap/3.3.5/css/bootstrap-theme.min.css"></head><body><div class="container"><canvas id="myCanvas_bottom" style="border:1px solid #d3d3d3;position: absolute;">Your browser does not support the HTML5 canvas tag.</canvas><canvas id="myCanvas_top" style="border:1px solid #d3d3d3;position: absolute;">Your browser does not support the HTML5 canvas tag.</canvas></div><script type="text/javascript">var w = 800;var h = 80;var mousedown = false;//设置底部canvas样式等var canvas_bottom = document.getElementById('myCanvas_bottom');canvas_bottom.width = w;canvas_bottom.height = h;canvas_bottom_ctx = canvas_bottom.getContext('2d');canvas_bottom_ctx.font = '30px Verdana';canvas_bottom_ctx.textAlign = 'left';var gradient = canvas_bottom_ctx.createLinearGradient(0, 0, canvas_bottom.width, 0);gradient.addColorStop(0, 'magenta');gradient.addColorStop(0.5, 'blue');gradient.addColorStop(1, 'red');canvas_bottom_ctx.strokeStyle = gradient;canvas_bottom_ctx.strokeText('谢谢惠顾，感谢您这次的选择', 10, 50); //可自由设定//设置顶部canvasvar canvas_top = document.getElementById('myCanvas_top');canvas_top.width = w;canvas_top.height = h;var offsetX = canvas_top.offsetLeft;var offsetY = canvas_top.offsetTop;canvas_top_ctx = canvas_top.getContext('2d');canvas_top_ctx.fillStyle = 'gray';canvas_top_ctx.fillRect(0, 0, w, h);canvas_top_ctx.globalCompositeOperation = 'destination-out';canvas_top.addEventListener('touchstart', eventDown);canvas_top.addEventListener('touchend', eventUp);canvas_top.addEventListener('touchmove', eventMove);canvas_top.addEventListener('mousedown', eventDown);canvas_top.addEventListener('mouseup', eventUp);canvas_top.addEventListener('mousemove', eventMove);function eventDown(e){        e.preventDefault();        mousedown=true;    }    function eventUp(e){        e.preventDefault();        mousedown=false;    }    function eventMove(e){        e.preventDefault();        if(mousedown) {             if(e.changedTouches){                 e=e.changedTouches[e.changedTouches.length-1];             }             var x = (e.clientX + document.body.scrollLeft || e.pageX) - offsetX || 0;             var y = (e.clientY + document.body.scrollTop || e.pageY) - offsetY || 0;             with(canvas_top_ctx) {                 beginPath()                 arc(x, y, 10, 0, Math.PI * 2);                 fill();             }        }    }</script></body></html>
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