js+canvas實現刮刮獎功能
本文實例為大家分享了js+canvas實現刮刮獎的具體代碼，供大家參考，具體內容如下
1.實現了PC端的刮刮獎效果
2.使用了canvas的文本，像素操作，合成，繪制圖形，隨機數
<!DOCTYPE html><html> <head> <meta charset='UTF-8'> <title>刮刮獎</title> <style type='text/css'> * { margin: 0; padding: 0; } .box { width: 500px; height: 500px; margin: 0 auto; position: relative; background: #00BFFF; } #prize { width: 300px; height: 100px; position: absolute; top: 50%; left: 50%; margin: -50px 0 0 -150px; background: #fff; font-family: '微軟雅黑'; font-size: 40px; text-align: center; line-height: 100px; -webkit-user-select: none; } #myCanvas { position: absolute; top: 50%; left: 50%; margin: -50px 0 0 -150px; } </style> </head> <body> <div class='box'> <div id='prize'></div> <canvas height='100'></canvas> </div> </body> <script type='text/javascript'> //獲取對象 var textArr = ['一等獎', '二等獎', '三等獎', '謝謝惠顧', '再來一次']; var prize = document.getElementById('prize'); var num = Math.random() * 100; if (num <= 60) { prize.innerText = textArr[3]; } else if (num <= 70) { prize.innerText = textArr[4]; } else if (num <= 80) { prize.innerText = textArr[2]; } else if (num <= 90) { prize.innerText = textArr[1]; } else if (num <= 100) { prize.innerText = textArr[0]; } var myCanvas = document.getElementById('myCanvas'); // 搭建環境 var cxt = myCanvas.getContext('2d'); cxt.globalAlpha = 1; cxt.fillStyle = '#ccc'; cxt.fillRect(0, 0, 300, 100); var txt = '刮刮獎'; cxt.fillStyle = '#000'; cxt.font = '30px 微軟雅黑'; cxt.textAlign = 'center'; cxt.textBaseline = 'middle'; cxt.fillText(txt, 150, 50, 300); var mX, mY; var flag = false; myCanvas.onmousedown = function(e) { flag = true; mX = e.offsetX; mY = e.offsetY; drawArc(mX, mY); } document.body.onmousemove = function(e) { if (flag == true) { mX = e.offsetX; mY = e.offsetY; drawArc(mX, mY); } } document.body.onmouseup = function() { flag = false; sayPrize(); } function drawArc(x, y) { cxt.globalCompositeOperation = 'destination-out'; //相交部分不顯示 cxt.beginPath(); cxt.fillStyle = 'white'; cxt.moveTo(x, y); cxt.arc(x, y, 10, 0, 2 * Math.PI); cxt.fill(); } function sayPrize() { var myImg = cxt.getImageData(70, 30, 160, 40); // var myImg = cxt.getImageData(93, 37, 40, 30); // 設置像素點的顏色 var num = 0; var max = myImg.data.length / 4; for (var i = 0; i < myImg.data.length; i += 4) { if (myImg.data[i + 3] <= 200) { num++; } } //2/3*myImg.data.length/4 if (num >= max * 0.6) { alert('恭喜您,獲得：' + prize.innerText); } } </script></html>
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持好吧啦網。
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