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canvas var 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>
