站长资讯网利用Html 5的canvas标签绘制水流和水池动画
在利用HTML 5的canvas进行动画绘制之前，首先先介绍一下基本知识，包括canvas（如果对canvas比较熟悉的可以直接跳过该节）、oCanvas框架、精灵动画。在了解了以上的基本知识后，就可以开始利用canvas做动画了。
canvas标签简介
在这部分，东西比较多，比较杂，各个网站上都可以找到相关的简介，在此我就不造轮子了，菜鸟上的教程就挺不错的，另外推荐一个相当好的博文玩转html 5 canvas画图,这篇文章介绍的非常详细，推荐好好看看。
canvas框架oCanvas简介
canvas标签功能非常强大，既可以处理图片，又可以进行像素级的处理，完全可以取代浏览器端的flash，但是由于canvas发展还未完善，API还不是太全，元素的事件处理功能等还没有提供接口，在实现一些复杂功能时，尚需耗费许多精力，于是出现了许多第三方的基于canvas 的框架，这些框架相比于原生的canvas标签，有了更多简单易用的API，大大提高了我们编码的效率，在这里我选用的是oCanvas框架，相关的使用文档和demo都可以去上面的链接中查看。
精灵动画简介
精灵动画一般由一组自定义的属性值和3个子函数组成（init、advance、draw）。
三个函数的作用分别如下：
init：初始化精灵动画的属性值
advance：再画下一帧之前首先更新下一帧的状态值
draw：将advance函数中更新的状态值绘制到画布中
以上三个函数的执行顺序是：init->advance->draw->advance->draw->…..一直循环下去。下面我以一个随机产生上升气泡的例子说明一下上面的执行过程。
var constructor_bubble = function (settings, core) { return oCanvas.extend({ core: core, shapeType: "rectangular",//下面定义了上面我们提到的三个函数：init(),advance(),draw()//在init中，我们map对象组、一个空的数组和一个代表高度的属性值 init: function () { this.map=[ {r:2,speed:3}, {r:3,speed:3}, {r:4,speed:3}, {r:5,speed:3}, {r:6,speed:3}, {r:7,speed:3}, {r:8,speed:3}, {r:9,speed:3}, {r:10,speed:3} ]; this.points=[]; this.height=this.container.height_now; },//下面是advance函数，在函数中我们利用if逻辑判断是否添加新的气泡以及进行气泡的位置更新，points数组利用队列的先进先出来存储气泡的 advance: function () { this.height=this.container.height_now; if(Math.random()>0.95){ var new_point={ x:this.start.x+this.offset*2*(Math.random()-0.5), y:this.start.y-this.map[0].r, r:this.map[0].r }; this.points.push(new_point); } if(this.points.length>0){ for(var i=0;i<this.points.length;i++){ this.points[i].x+=this.offset*2*(Math.random()-0.5); this.points[i].y-=3; if(this.start.y-this.points[i].y>this.height-this.points[i].r-33){ this.points.shift(); } } } },//draw函数中，利用canvas的圆弧绘制指令，将points数组中存储的气泡依次画出 draw: function () { var canvas = this.core.canvas; canvas.lineJoin = 'round'; canvas.lineWidth = this.GDwidth; canvas.strokeStyle = "#fff"; if(this.points.length>0){ for(var i=0;i<this.points.length;i++){ canvas.beginPath(); canvas.arc(this.points[i].x,this.points[i].y,5,0,2*Math.PI); canvas.stroke(); canvas.closePath(); } } } }, settings); }; oCanvas.registerDisplayObject("bubble", constructor_bubble, "init");//下面是在应用中定义和添加上面定义的精灵动画，其中：start数组代表了气泡的产生点，container代表了气泡的存在区域var pp1=canvas.display.bubble({ start:{x:425,y:566}, container:SC02, width:50, offset:1, speed:5 }).add();
水流和水池动画实现
下面详细介绍一下，项目中如何实现水流动画和水池动画的详细步骤：
水池动画的绘制
var constructor_show = function (settings, core) { return oCanvas.extend({ core: core, shapeType: "rectangular",//上面四行都是oCanvas框架的结构语法/*下面init()、advance（）、draw()分别是上节中说的动画精灵三元素，第一个用来初始化，第二个用来 更新操作，第三个用来绘制图像/动画在管道对象中，定义了一些属性，包括：x、y、height、width、start、 height_now、full、speed、fill、trail_flag、[trail]。其中x、y分别代表水池参考点相对画布左 上角的位置，height、width是水池的宽高属性，start表征了动画是否开始，height_now代表了水池中水 位的高度，full表征了水池是否填满，speed水池上涨的速度，fill水的颜色，trail_flag表征了该水池 是否是一个标准的矩形，如果不是的话，配合trail属性，指定水池的轮廓*/ init: function () { //默认动画关闭，水池full为0，当前高度为0 this.start=0; this.full=0; this.height_now=0; }, advance: function () { //如果水池未满并且是开启状态，水位未满就更新当前高度，否则将full置为1 if(this.start==1&&this.full!=1){ if (this.height_now < this.Height) { this.height_now += this.speed; } else { this.full = 1; } } }, draw: function () { var canvas = this.core.canvas, //先获得水池的位置 origin = this.getOrigin(), x = this.abs_x - origin.x, y = this.abs_y - origin.y; //开始绘制 canvas.beginPath(); canvas.strokeStyle = "#000"; if (this.trail_flag == 1) { //如果是不规则图形，描出轮廓 canvas.moveTo(this.trail[0].x_t, this.trail[0].y_t); for (var i = 1; i < this.trail.length; i++) { canvas.lineTo(this.trail[i].x_t, this.trail[i].y_t); } canvas.lineTo(this.trail[0].x_t, this.trail[0].y_t); canvas.clip(); } if (this.fill !== "") { //设置颜色，绘制矩形水池 canvas.fillStyle = this.fill; canvas.fillRect(x, y + this.Height - this.height_now, this.Width, this.height_now); } canvas.closePath(); } }, settings); };//将上面的动画精灵注册进oCanvas的display图形库中oCanvas.registerDisplayObject("SC_show", constructor_show, "init");
管道水流动画的绘制
在管道水流模型中，定义了以下的属性：
destination: 当前水流最前端的位置
cells: 管道路径数组
deta: 方向斜边长
deta_x: 方向x边长
deta_y: 方向y边长
flag_x: 余弦值
flag_y:正弦值
cellIndex: 当前绘制边的index
Speed: 水流速度
GDwidth:水流宽度
LineHeight:水流长度
x_now: 当前绘制点x坐标
y_now: 当前绘制点y坐标
firstX: 管道第一个点坐标x
firstY: 管道第一个点坐标y
beginHeight: 第一段水流的起点位置
endHeight: 上一段管道遗留未画完的水线
legacyHeight: 最前端点在上一个管道留下的长度
paused: 是否开始
fill:水流颜色
full:是否填满
init函数
//init函数主要完成初始化工作init: function () { this.x_now = this.cells[0].x_cell; this.y_now = this.cells[0].y_cell; this.firstX = this.x_now; this.firstY = this.y_now; this.endHeight = 0; this.beginHeight = 0; this.paused=0; this.full=0; this.cellIndex = 0; this.destination.x_d = this.cells[0].x_cell; this.destination.y_d = this.cells[0].y_cell; this.legacyHeight = -1; this.LineHeight=10; this.Speed=2*this.LineHeight/20; }
advance函数
//advance函数主要实现每次动画的刷新步进操作 advance: function () { if(this.paused==1){ if (this.cellIndex < this.cells.length - 1) { this.deta_x = this.cells[this.cellIndex + 1].x_cell - this.cells[this.cellIndex].x_cell; this.deta_y = this.cells[this.cellIndex + 1].y_cell - this.cells[this.cellIndex].y_cell; this.deta = Math.sqrt(this.deta_x * this.deta_x + this.deta_y * this.deta_y); this.flag_x = this.deta_x / this.deta; this.flag_y = this.deta_y / this.deta; if (this.legacyHeight >= 0) { this.cellIndex++; if (this.cellIndex < this.cells.length - 1) { this.deta_x = this.cells[this.cellIndex + 1].x_cell - this.cells[this.cellIndex].x_cell; this.deta_y = this.cells[this.cellIndex + 1].y_cell - this.cells[this.cellIndex].y_cell; this.deta = Math.sqrt(this.deta_x * this.deta_x + this.deta_y * this.deta_y); this.flag_x = this.deta_x / this.deta; this.flag_y = this.deta_y / this.deta; this.destination.x_d = this.cells[this.cellIndex].x_cell + this.flag_x * this.legacyHeight; this.destination.y_d = this.cells[this.cellIndex].y_cell + this.flag_y * this.legacyHeight; if (Math.abs(this.destination.x_d - this.cells[this.cellIndex + 1].x_cell) > this.Speed * Math.abs(this.flag_x) || Math.abs(this.destination.y_d - this.cells[this.cellIndex + 1].y_cell) > this.Speed * Math.abs(this.flag_y)) { this.legacyHeight = -1; this.destination.x_d += this.flag_x * this.Speed; this.destination.y_d += this.flag_y * this.Speed; } else { if (this.flag_x == 0) { this.legacyHeight = this.Speed - Math.abs(this.destination.y_d - this.cells[this.cellIndex + 1].y_cell) / Math.abs(this.flag_y); } else { this.legacyHeight = this.Speed - Math.abs(this.destination.x_d - this.cells[this.cellIndex + 1].x_cell) / Math.abs(this.flag_x); } } } } else { this.destination.x_d += this.flag_x * this.Speed; this.destination.y_d += this.flag_y * this.Speed; if (Math.abs(this.destination.x_d - this.cells[this.cellIndex + 1].x_cell) >= this.Speed * Math.abs(this.flag_x) && Math.abs(this.destination.y_d - this.cells[this.cellIndex + 1].y_cell) >= this.Speed * Math.abs(this.flag_y)) { this.legacyHeight = -1; } else { if (this.flag_x == 0) { this.legacyHeight = this.Speed - Math.abs(this.destination.y_d - this.cells[this.cellIndex + 1].y_cell) / Math.abs(this.flag_y); } else { this.legacyHeight = this.Speed - Math.abs(this.destination.x_d - this.cells[this.cellIndex + 1].x_cell) / Math.abs(this.flag_x); } } } }else{ this.full=1; } this.deta_x = this.cells[1].x_cell - this.cells[0].x_cell; this.deta_y = this.cells[1].y_cell - this.cells[0].y_cell; this.deta = Math.sqrt(this.deta_x * this.deta_x + this.deta_y * this.deta_y); this.flag_x = this.deta_x / this.deta; this.flag_y = this.deta_y / this.deta; if (this.paused == 1) { if (Math.abs(this.firstX - this.cells[0].x_cell) >= this.LineHeight * Math.abs(this.flag_x) && Math.abs(this.firstY - this.cells[0].y_cell) >= this.LineHeight * Math.abs(this.flag_y)) { this.firstX = this.cells[0].x_cell; this.firstY = this.cells[0].y_cell; this.beginHeight = 0; } else { if (this.beginHeight < this.LineHeight) { if (this.beginHeight + this.Speed >= this.LineHeight) { this.beginHeight = this.LineHeight; } else { this.beginHeight += this.Speed; } this.firstX = this.cells[0].x_cell; this.firstY = this.cells[0].y_cell; } else if (this.beginHeight == this.LineHeight) { this.firstX += this.flag_x * this.Speed; this.firstY += this.flag_y * this.Speed; } } } } }
draw函数
//draw函数在每次advance之后执行，将每次的步进更新重新绘制到画布上 draw: function () { var canvas = this.core.canvas; this.x_now = this.firstX; this.y_now = this.firstY; this.deta_x = this.cells[1].x_cell - this.cells[0].x_cell; this.deta_y = this.cells[1].y_cell - this.cells[0].y_cell; this.deta = Math.sqrt(this.deta_x * this.deta_x + this.deta_y * this.deta_y); var myEnd = false; this.flag_x = this.deta_x / this.deta; this.flag_y = this.deta_y / this.deta; canvas.beginPath(); canvas.lineJoin = 'round'; canvas.lineCap="round"; this.endHeight = 0; canvas.lineWidth = this.GDwidth / 4; canvas.strokeStyle = this.fill; if (this.beginHeight > 0) { canvas.moveTo(this.x_now, this.y_now); canvas.lineTo(this.x_now + this.flag_x * this.beginHeight, this.y_now + this.flag_y * this.beginHeight); } this.x_now += this.flag_x * (this.beginHeight + this.LineHeight); this.y_now += this.flag_y * (this.beginHeight + this.LineHeight); for (var i = 1; i <= this.cellIndex; i++) { myEnd = false; this.deta_x = this.cells[i].x_cell - this.cells[i - 1].x_cell; this.deta_y = this.cells[i].y_cell - this.cells[i - 1].y_cell; this.deta = Math.sqrt(this.deta_x * this.deta_x + this.deta_y * this.deta_y); this.flag_x = this.deta_x / this.deta; this.flag_y = this.deta_y / this.deta; if (this.endHeight > 0) { canvas.moveTo(this.cells[i - 1].x_cell, this.cells[i - 1].y_cell); canvas.lineTo(this.cells[i - 1].x_cell + this.flag_x * (this.endHeight ), this.cells[i - 1].y_cell + this.flag_y * this.endHeight); this.x_now = this.cells[i - 1].x_cell + this.flag_x * (this.LineHeight + this.endHeight); this.y_now = this.cells[i - 1].y_cell + this.flag_y * (this.LineHeight + this.endHeight); } if (this.endHeight < 0) { this.endHeight = Math.abs(this.endHeight); this.x_now = this.cells[i - 1].x_cell + this.flag_x * (this.endHeight); this.y_now = this.cells[i - 1].y_cell + this.flag_y * (this.endHeight); } if (this.endHeight == 0 && i != 1) { this.x_now = this.cells[i - 1].x_cell; this.y_now = this.cells[i - 1].y_cell; } while (Math.abs(this.x_now - this.cells[i].x_cell) >= this.LineHeight * Math.abs(this.flag_x) && Math.abs(this.y_now - this.cells[i].y_cell) >= this.LineHeight * Math.abs(this.flag_y)) { canvas.moveTo(this.x_now, this.y_now); canvas.lineTo(this.x_now + this.flag_x * this.LineHeight, this.y_now + this.flag_y * this.LineHeight); this.x_now += this.flag_x * this.LineHeight; this.y_now += this.flag_y * this.LineHeight; if (Math.abs(this.x_now - this.cells[i].x_cell) <= this.LineHeight * Math.abs(this.flag_x) && Math.abs(this.y_now - this.cells[i].y_cell) <= this.LineHeight * Math.abs(this.flag_y)) { if (this.flag_x == 0) { this.endHeight = Math.abs(this.y_now - this.cells[i].y_cell) / Math.abs(this.flag_y) - this.LineHeight; } else { this.endHeight = Math.abs(this.x_now - this.cells[i].x_cell) / Math.abs(this.flag_x) - this.LineHeight; } //this.endHeight = (Math.abs(this.y_now - this.cells[i].y_cell) + Math.abs(this.x_now - this.cells[i].x_cell) - this.LineHeight * (Math.abs(this.flag_y) + Math.abs(this.flag_x)))/2; myEnd = true; break; } else { this.x_now += this.flag_x * this.LineHeight; this.y_now += this.flag_y * this.LineHeight; } } if (myEnd == false && Math.abs(this.x_now - this.cells[i].x_cell) <= this.LineHeight * Math.abs(this.flag_x) && Math.abs(this.y_now - this.cells[i].y_cell) <= this.LineHeight * Math.abs(this.flag_y)) { canvas.moveTo(this.x_now, this.y_now); canvas.lineTo(this.cells[i].x_cell, this.cells[i].y_cell); //this.endHeight = this.LineHeight - Math.abs(this.x_now - this.cells[i].x_cell)*flag.x_flag - Math.abs(this.y_now - this.cells[i].y_cell)*flag.y_flag; if (this.flag_x == 0) { this.endHeight = this.LineHeight - Math.abs(this.y_now - this.cells[i].y_cell) / Math.abs(this.flag_y); } else { this.endHeight = this.LineHeight - Math.abs(this.x_now - this.cells[i].x_cell) / Math.abs(this.flag_x); } //this.endHeight = ( this.LineHeight * (Math.abs(this.flag_y) + Math.abs(this.flag_x)) - Math.abs(this.y_now - this.cells[i].y_cell) + Math.abs(this.x_now - this.cells[i].x_cell)) / 2; } } if (this.cellIndex < this.cells.length - 1) { myEnd = false; this.deta_x = this.cells[this.cellIndex+1].x_cell-this.destination.x_d; this.deta_y = this.cells[this.cellIndex+1].y_cell-this.destination.y_d; this.deta = Math.sqrt(this.deta_x * this.deta_x + this.deta_y * this.deta_y); if (this.deta > 0) { this.flag_x = this.deta_x / this.deta; this.flag_y = this.deta_y / this.deta; if (this.endHeight > 0) { canvas.moveTo(this.cells[this.cellIndex].x_cell, this.cells[this.cellIndex].y_cell); canvas.lineTo(this.cells[this.cellIndex].x_cell + this.flag_x * (this.endHeight ), this.cells[this.cellIndex].y_cell + this.flag_y * this.endHeight); this.x_now = this.cells[this.cellIndex].x_cell + this.flag_x * ( this.endHeight); this.y_now = this.cells[this.cellIndex].y_cell + this.flag_y * ( this.endHeight); if(Math.abs(this.destination.x_d-this.x_now)>this.LineHeight*Math.abs(this.flag_x)||Math.abs(this.destination.y_d-this.y_now)>this.LineHeight*Math.abs(this.flag_y)){ this.x_now+=this.LineHeight*this.flag_x; this.y_now+=this.LineHeight*this.flag_y; } else{ this.x_now=this.destination.x_d; this.y_now=this.destination.y_d; } if (this.endHeight < 0) { this.endHeight = Math.abs(this.endHeight); this.x_now = this.cells[this.cellIndex].x_cell + this.flag_x * (this.endHeight); this.y_now = this.cells[this.cellIndex].y_cell + this.flag_y * (this.endHeight); } if (this.endHeight == 0 && this.cellIndex > 0) { this.x_now = this.cells[this.cellIndex].x_cell; this.y_now = this.cells[this.cellIndex].y_cell; } if (this.cellIndex == 0) { this.x_now = this.firstX; this.y_now = this.firstY; if (this.beginHeight > 0) { canvas.moveTo(this.x_now, this.y_now); canvas.lineTo(this.x_now + this.flag_x * this.beginHeight, this.y_now + this.flag_y * this.beginHeight); } this.x_now += this.flag_x * (this.beginHeight + this.LineHeight); this.y_now += this.flag_y * (this.beginHeight + this.LineHeight); } while ((Math.abs(this.x_now - this.destination.x_d) >= this.LineHeight * Math.abs(this.flag_x) && Math.abs(this.y_now - this.destination.y_d) >this.LineHeight * Math.abs(this.flag_y))||(Math.abs(this.x_now - this.destination.x_d) > this.LineHeight * Math.abs(this.flag_x) && Math.abs(this.y_now - this.destination.y_d) >=this.LineHeight * Math.abs(this.flag_y))) { canvas.moveTo(this.x_now, this.y_now); canvas.lineTo(this.x_now + this.flag_x * this.LineHeight, this.y_now + this.flag_y * this.LineHeight); this.x_now += this.flag_x * this.LineHeight; this.y_now += this.flag_y * this.LineHeight; if (Math.abs(this.x_now - this.destination.x_d)<= this.LineHeight * Math.abs(this.flag_x)&&Math.abs(this.y_now - this.destination.y_d) <= this.LineHeight * Math.abs(this.flag_y)) { myEnd = true; break; } else { this.x_now += this.flag_x * this.LineHeight; this.y_now += this.flag_y * this.LineHeight; } } if (myEnd == false && Math.abs(this.x_now - this.destination.x_d) < this.LineHeight * Math.abs(this.flag_x) || Math.abs(this.y_now - this.destination.y_d) < this.LineHeight * Math.abs(this.flag_y)) { canvas.moveTo(this.x_now, this.y_now); canvas.lineTo(this.destination.x_d, this.destination.y_d); } } } canvas.stroke(); canvas.closePath(); }
取水泵房的实例
下面代码在定义了一个水池对象，并赋予了相应的属性值，最后将定义的对象添加到ｃａｎｖａｓ画布中。
var SC01 = canvas.display.SC_show({ x: 326, y: 200, Width: 181, Height: 438, height_now: 0, trail_flag: 0, t: 0, fill: color_SC, speed:speed_SC, full:0, start:0 });canvas.addChild(SC01);
下面的代码定义了一个管道对象，并且给管道对象赋予了一些初始值，最后添加到ｃａｎｖａｓ画布中。
var GD01 = canvas.display.GD({ x: 0, y: 0, destination: { x_d: 0, y_d: 0 }, cells: [ {x_cell: 195, y_cell: 587}, {x_cell: 335, y_cell: 587} ], deta: 1, deta_x: 1, deta_y: 0, flag_x: 1, flag_y: 0, cellIndex: 0, Speed: speed_all, GDwidth: width_all, LineHeight: 10, x_now: 0, y_now: 0, firstX: 0, firstY: 0, beginHeight: 0, endHeight: 0, legacyHeight: 0, paused: 1, fill:color_GD, full:0 }); canvas.addChild(GD01);
具体动画的流程控制如下：
canvas.setLoop(function () { ／／下面６个ａｄｖａｎｃｅ函数实现每一帧中的动画对象的更新操作 GD01.advance(); SC01.advance(); SC02.advance(); GD02.advance(); SC03.advance(); GD03.advance(); ／／下面几个ｉｆ语句实现动画的流程控制 if(GD01.full==1){ SC01.start = 1; SC02.start = 1; } if(SC02.full==1){ GD02.paused = 1; } if(GD02.full==1) { SC03.start = 1; arrow_1.start(); arrow_2.start(); } if(SC03.full==1) { GD03.paused = 1; } canvas.redraw(); ／／重绘画布 }).start(); ／／循环开始
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