canvas刮刮乐和画笔
这周有点迷茫，不知道干嘛了，一天天就过去了！我在博客右侧公告栏加了qq交流，各位有好的主题，或者有趣的技术，欢迎交流！今天突发奇想，就写了2个h5 canvas的demo玩玩！
demo一：刮刮乐
舍不得买2块钱的刮刮乐，就只能写个类似的功能过过彩票瘾了！
布局
<div id="lottery" style="width:300px;height:500px;margin:10px;background-color:lightskyblue;border-radius:5px;float:left;"> <div style="width:300px;height:100px;line-height:100px;text-align:center;font-size:33px;color:blueviolet;">NICK彩票</div> <div id="txt" style="width:300px;height:200px;font-size:40px;color:peachpuff;display:flex;justify-content:center;align-items:center;flex-direction:column;"> <span>祝</span> <span>君</span> <span>中</span> <span>奖</span> </div> <div id="canvasArea" style="width:300px;height:200px;position:relative;"> <div style="width:300px;height:200px;position:absolute;top:0;left:0;z-index:1;text-align:center;line-height:200px;font-weight:bold;font-size:56px;color:indianred;">一等奖</div> <canvas id="canvas" width="300px" height="200px" style="position:absolute;top:0;left:0;z-index:2;"></canvas> </div> </div>
这段html要注意的地方有2个：
- flex布局，将‘祝君中奖’垂直居中，目前还有兼容问题，不过看我们大前端的发展趋势，应该很快就能搞定了；
- canvas和‘一等奖’div的z-index问题，将canvas的z-index设置较高，使其置于一等奖div上面。
设置canvas画布
var canvas = document.getElementById("canvas"); var context = canvas.getContext("2d");
绘制刮奖区域
context.fillStyle='#A9AB9D'; context.fillRect(10,10,280,180); context.fillStyle='#000'; context.font='50px Arial'; context.fillText('刮奖区',75,115);
- 填充颜色；
- 绘制实心矩形；
- 设置字体颜色；
- 设置字体大小类型；
- 绘制实心字体。
以上都是canvas基础api，看w3c就ok了。
为了好看，我将‘祝君中奖’加个字体变色
setInterval(function(){ document.getElementById('txt').style.color = document.getElementById('txt').style.color=='peachpuff' ? 'yellow' : 'peachpuff'; },500);
刮奖功能函数
var brush=function(){//刮奖 context.clearRect(event.offsetX,event.offsetY,20,20); };
为canvas元素onmousedown和onmouseup事件
canvas.onmousedown = function(){ // 鼠标按下时 - 绑定鼠标跟随事件 bindHandler(canvas,'mousemove',brush,false); } canvas.onmouseup = function(){ // 停止刮奖功能 - 解绑鼠标跟随事件 removeHandler(canvas,"mousemove",brush,false); }
这里的事件绑定与解绑我上篇博文有封装，最后完整代码也有！
刮刮乐happy到底结束！最后附上完整代码，再看看效果吧！
demo二：画笔
布局
<div style="width:300px;height:500px;margin:10px;border-radius:10px;overflow:hidden;float:right;"> <canvas id="canvas2" width="300px" height="500px" style="background-color:lightblue;"></canvas> </div>
设置canvas画布
var canvas2 = document.getElementById("canvas2"); var context2 = canvas2.getContext("2d");
画笔功能函数
var draw=function(){ context2.fillRect(event.offsetX,event.offsetY,10,10); };
为canvas元素onmousedown和onmouseup事件
context2.font='20px Arial'; context2.strokeText('NICK画笔',100,30);//写个头 //1. 为canvas元素onmousedown和onmouseup事件 canvas2.onmousedown = function(){ // 启用画笔功能 - 绑定鼠标跟随事件 bindHandler(canvas2,'mousemove',draw,false); } canvas2.onmouseup = function(){ // 停止画笔功能 - 解绑鼠标跟随事件 removeHandler(canvas2,"mousemove",draw,false); }
画图工具的画笔功能到底结束！
多谢各位老司机的鞭策与提醒，说画笔功能有不连续的现象！
现已改良，并兼容了移动端！
//改良后的写法
var isTouch = "ontouchstart" in window ? true : false;
var StartDraw = isTouch ? "touchstart" : "mousedown",
MoveDraw = isTouch ? "touchmove" : "mousemove",
EndDraw = isTouch ? "touchend" : "mouseup";
context2.strokeStyle='blue';//线色
context2.lineCap = "round";//连接处为圆形
context2.lineWidth =10;//线框
canvas2.addEventListener(StartDraw, function(ev){
ev.preventDefault();
var isX = isTouch ? ev.targetTouches[0].pageX : ev.pageX;
var isY = isTouch ? ev.targetTouches[0].pageY : ev.pageY;
var x = isX - canvas2.offsetLeft;
var y = isY - canvas2.offsetTop;
context2.beginPath();
context2.moveTo(x, y);
function StartMove(ev){
var isX1 = isTouch ? ev.targetTouches[0].pageX : ev.pageX;
var isY1 = isTouch ? ev.targetTouches[0].pageY : ev.pageY;
var x1 = isX1 - canvas2.offsetLeft;
var y1 = isY1 - canvas2.offsetTop;
context2.lineTo(x1, y1);
context2.stroke();
context2.beginPath();
context2.moveTo(x1, y1);
};
function EndMove(ev){
var isX1 = isTouch ? ev.changedTouches[0].pageX : ev.pageX;
var isY1 = isTouch ? ev.changedTouches[0].pageY : ev.pageY;
var x1 = isX1 - canvas2.offsetLeft;
var y1 = isY1 - canvas2.offsetTop;
context2.lineTo(x1, y1);
context2.stroke();
canvas2.removeEventListener(MoveDraw, StartMove, false);
canvas2.removeEventListener(EndDraw, EndMove, false);
};
canvas2.addEventListener(MoveDraw, StartMove, false);
canvas2.addEventListener(EndDraw, EndMove, false);
}, false);
附上完整代码：
<!DOCTYPE html> <html> <head> <title>Canvas lottery brush nick</title> <meta charset="utf-8"/> </head> <body> <div style="width:640px;margin:auto;"> <!--刮刮乐--> <div id="lottery" style="width:300px;height:500px;margin:10px;background-color:lightskyblue;border-radius:5px;float:left;"> <div style="width:300px;height:100px;line-height:100px;text-align:center;font-size:33px;color:blueviolet;">NICK彩票</div> <div id="txt" style="width:300px;height:200px;font-size:40px;color:peachpuff;display:flex;justify-content:center;align-items:center;flex-direction:column;"> <span>祝</span> <span>君</span> <span>中</span> <span>奖</span> </div> <div id="canvasArea" style="width:300px;height:200px;position:relative;"> <div style="width:300px;height:200px;position:absolute;top:0;left:0;z-index:1;text-align:center;line-height:200px;font-weight:bold;font-size:56px;color:indianred;">一等奖</div> <canvas id="canvas" width="300px" height="200px" style="position:absolute;top:0;left:0;z-index:2;"></canvas> </div> </div> <!--画图工具画笔功能--> <div style="width:300px;height:500px;margin:10px;border-radius:10px;overflow:hidden;float:right;"> <canvas id="canvas2" width="300px" height="500px" style="background-color:lightblue;"></canvas> </div> </div> <div style="text-align:center;"> <p>刮刮乐：鼠标按住不放，拖动开始刮奖！</p> <p>画笔：鼠标按住不放，拖动画画！</p> </div> <script> //插件方法封装区 ;(function(){ // 事件绑定 window.bindHandler = (function() { if (window.addEventListener) {// 标准浏览器 return function(elem, type, handler) { // elem:节点 type:事件类型 handler:事件处理函数 // 最后一个参数为true:在捕获阶段调用事件处理程序;为false:在冒泡阶段调用事件处理程序。注意：ie没有这个参数 elem.addEventListener(type, handler, false); } } else if (window.attachEvent) {// IE浏览器 return function(elem, type, handler) { elem.attachEvent("on" + type, handler); } } }()); // 事件解除 window.removeHandler = (function() { if (window.removeEventListener) {// 标准浏览器 return function(elem, type, handler) { elem.removeEventListener(type, handler, false); } } else if (window.detachEvent) {// IE浏览器 return function(elem, type, handler) { elem.detachEvent("on" + type, handler); } } }()); }()); //命名区 var canvas = document.getElementById("canvas"); var context = canvas.getContext("2d"); var canvas2 = document.getElementById("canvas2"); var context2 = canvas2.getContext("2d"); var brush=function(){//刮奖 context.clearRect(event.offsetX,event.offsetY,20,20); }; var draw=function(){//写字 context2.fillRect(event.offsetX,event.offsetY,10,10); }; //功能实现区 //刮刮乐 // 1. 绘制刮奖区域 context.fillStyle='#A9AB9D'; context.fillRect(10,10,280,180); context.fillStyle='#000'; context.font='50px Arial'; context.fillText('刮奖区',75,115); //字体变色 setInterval(function(){ document.getElementById('txt').style.color = document.getElementById('txt').style.color=='peachpuff' ? 'yellow' : 'peachpuff'; },500); //2. 为canvas元素onmousedown和onmouseup事件 canvas.onmousedown = function(){ // 鼠标按下时 - 绑定鼠标跟随事件 bindHandler(canvas,'mousemove',brush,false); } canvas.onmouseup = function(){ // 停止刮奖功能 - 解绑鼠标跟随事件 removeHandler(canvas,"mousemove",brush,false); } //画笔 context2.font='20px Arial'; context2.strokeText('NICK画笔',100,30);//写个头 //为canvas元素onmousedown和onmouseup事件 /* //这是原来的写法 canvas2.onmousedown = function(){ // 启用画笔功能 - 绑定鼠标跟随事件 bindHandler(canvas2,'mousemove',draw,false); } canvas2.onmouseup = function(){ // 停止画笔功能 - 解绑鼠标跟随事件 removeHandler(canvas2,"mousemove",draw,false); } */ //改良后的写法 var isTouch = "ontouchstart" in window ? true : false; var StartDraw = isTouch ? "touchstart" : "mousedown", MoveDraw = isTouch ? "touchmove" : "mousemove", EndDraw = isTouch ? "touchend" : "mouseup"; context2.strokeStyle='blue';//线色 context2.lineCap = "round";//连接处为圆形 context2.lineWidth =10;//线框 canvas2.addEventListener(StartDraw, function(ev){ ev.preventDefault(); var isX = isTouch ? ev.targetTouches[0].pageX : ev.pageX; var isY = isTouch ? ev.targetTouches[0].pageY : ev.pageY; var x = isX - canvas2.offsetLeft; var y = isY - canvas2.offsetTop; context2.beginPath(); context2.moveTo(x, y); function StartMove(ev){ var isX1 = isTouch ? ev.targetTouches[0].pageX : ev.pageX; var isY1 = isTouch ? ev.targetTouches[0].pageY : ev.pageY; var x1 = isX1 - canvas2.offsetLeft; var y1 = isY1 - canvas2.offsetTop; context2.lineTo(x1, y1); context2.stroke(); context2.beginPath(); context2.moveTo(x1, y1); }; function EndMove(ev){ var isX1 = isTouch ? ev.changedTouches[0].pageX : ev.pageX; var isY1 = isTouch ? ev.changedTouches[0].pageY : ev.pageY; var x1 = isX1 - canvas2.offsetLeft; var y1 = isY1 - canvas2.offsetTop; context2.lineTo(x1, y1); context2.stroke(); canvas2.removeEventListener(MoveDraw, StartMove, false); canvas2.removeEventListener(EndDraw, EndMove, false); }; canvas2.addEventListener(MoveDraw, StartMove, false); canvas2.addEventListener(EndDraw, EndMove, false); }, false); </script> </body> </html>
代码写完了，我也想说点其他的：
上面js代码中，有不少注释，我将其分为几个区域：插件方法封装区、命名区、功能实现区、刮刮乐区以及画笔区等，我感觉这样写加上一些注释，能使代码能加简洁，便于以后的维护！当然这只是个人观点，欢迎各位点击我博客右边公告栏的qq交流交流！
最后附上：
上篇博文：事件绑定与解绑！（只是一个简单的封装）
来看看效果，玩玩吧！
