js面向对象实现canvas制作彩虹球喷枪效果

前段时间在研究canvas,感觉还挺好玩的,就写了一个小demo,效果如下:

js面向对象实现canvas制作彩虹球喷枪效果

第一次尝试用js面向对象的方式来写,经验不足,还请大家多多包涵。 

下面开始简单介绍代码: 

canvas画布:

代码如下:

<canvas id='canvas' width='1050' height='500' style='background:#333;overflow: hidden;'></canvas>

彩虹球的随机颜色是通过下面两个方法来实现的,在《js常用方法和一些封装(2) -- 随机数生成》中曾经提到过。

/**
 * 获取 0 ~ num的随机数(闭区间)
 */
function randomNum(num){
 return Math.floor(Math.random()*(num+1));
};

/**
 * 获取随机颜色(支持任意浏览器)
 */
function randomColor16(){
 //0-255 
 var r = randomNum(255).toString(16);
 var g = randomNum(255).toString(16);
 var b = randomNum(255).toString(16);
 //255的数字转换成十六进制
 if(r.length<2)r = "0"+r;
 if(g.length<2)g = "0"+g;
 if(b.length<2)b = "0"+b;
 return "#"+r+g+b;
};

       

每当我鼠标点下,其实是在一个矩形区域随机产生不同颜色的彩虹球,彩虹球出现的位置也是随机的,通过范围随机数来实现:

/*
 * 获取范围随机数 (闭区间)
 */
function randomRange(start,end){
 return Math.floor(Math.random()*(end-start+1))+start;
};

接下来是彩虹球的类,用面向对象来做。

//彩虹球的类
var ColorBall = function(){}

ColorBall.prototype.left = 0; //X轴
ColorBall.prototype.top = 0; //y轴
ColorBall.prototype.r = 10; //半径

在本案例中,鼠标相当于是彩虹球喷枪,我们也用面向对象的思想来设计它:

//RainbowBrush 彩虹球喷枪
RainbowBrush = function(){}

//生产小球数组的方法
RainbowBrush.prototype.getBalls = function(num){
 var colorBalls = [];
 for(var i = 0; i < num; i++){
  var ball = new ColorBall();
  colorBalls.push(ball);
 }
 return colorBalls;
}

//喷刷彩虹球
RainbowBrush.prototype.brush = function(context,balls,x,y){
 balls.forEach(function(ballIem){
  ballIem.x = randomRange(x - 6,x + 6);
  ballIem.y = randomRange(y - 6,y + 6);
  ballIem.r = 5;
  
  context.beginPath();
  context.fillStyle=randomColor16();
  context.arc(ballIem.x,ballIem.y,ballIem.r,0,Math.PI*2);
  context.fill();
 })
 
}

它有两个方法,一个是生产彩虹球,另一个是喷刷彩虹球。 

案例的主要逻辑如下:

var rainbowBrush = new RainbowBrush(); //初始化彩虹球喷枪
var balls = rainbowBrush.getBalls(1);

//当鼠标按下
canvasDom.onmousedown = function(){
 var flag = true;
 canvasDom.onmousemove = function(e){
  var x = e.clientX;
  var y = e.clientY;
  if(flag) rainbowBrush.brush(context,balls,x,y);
 }
 
 canvasDom.onmouseup = function(){
  flag = false;
 }
}

案例全部代码:

<!DOCTYPE html>
<html>
 <head>
  <meta charset="UTF-8">
  <title>彩虹球喷枪</title>
 </head>
 <body>
  <canvas id='canvas' width='1050' height='500' style='background:#333;overflow: hidden;'></canvas>
  
 </body>
 
 <script type="text/javascript">
 
  /**
   * 获取 0 ~ num的随机数(闭区间)
   */
  function randomNum(num){
   return Math.floor(Math.random()*(num+1));
  };

  /*
   * 获取范围随机数 (闭区间)
   */
  function randomRange(start,end){
   return Math.floor(Math.random()*(end-start+1))+start;
  };
  
  
  /**
   * 获取随机颜色(支持任意浏览器)
   */
  function randomColor16(){
   //0-255 
   var r = randomNum(255).toString(16);
   var g = randomNum(255).toString(16);
   var b = randomNum(255).toString(16);
   //255的数字转换成十六进制
   if(r.length<2)r = "0"+r;
   if(g.length<2)g = "0"+g;
   if(b.length<2)b = "0"+b;
   return "#"+r+g+b;
  };
  
  var canvasDom = document.getElementById('canvas');
  var context = canvasDom.getContext('2d');
  var maxWidth = 1050;
  var maxHeight = 500;
  

  //彩虹球的类
  var ColorBall = function(){}
  
  ColorBall.prototype.left = 0; //X轴
  ColorBall.prototype.top = 0; //y轴
  ColorBall.prototype.r = 10; //半径
  
  //RainbowBrush 彩虹球喷枪
  RainbowBrush = function(){}
  
  //生产小球数组的方法
  RainbowBrush.prototype.getBalls = function(num){
   var colorBalls = [];
   for(var i = 0; i < num; i++){
    var ball = new ColorBall();
    colorBalls.push(ball);
   }
   return colorBalls;
  }
  
  //喷刷彩虹球
  RainbowBrush.prototype.brush = function(context,balls,x,y){
   balls.forEach(function(ballIem){
    ballIem.x = randomRange(x - 6,x + 6);
    ballIem.y = randomRange(y - 6,y + 6);
    ballIem.r = 5;
    
    context.beginPath();
    context.fillStyle=randomColor16();
    context.arc(ballIem.x,ballIem.y,ballIem.r,0,Math.PI*2);
    context.fill();
   })
   
  }
  
  var rainbowBrush = new RainbowBrush(); //初始化彩虹球喷枪
  var balls = rainbowBrush.getBalls(1);

  //当鼠标按下
  canvasDom.onmousedown = function(){
   var flag = true;
   canvasDom.onmousemove = function(e){
    var x = e.clientX;
    var y = e.clientY;
    if(flag) rainbowBrush.brush(context,balls,x,y);
   }
   
   canvasDom.onmouseup = function(){
    flag = false;
   }
  }

 </script>
</html>