3D HTML5 Logo标志 超炫酷旋转特效

澳门新葡亰娱乐在线 2

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澳门新葡亰娱乐在线 2

HTML代码:

<div style="width:530px;margin:10px auto">
    <div id="canvasDiv"></div>
</div>

HTML代码非常简单,仅仅是构造了一个canvas容器,我们的画板就在这个地方生成。

这部分代码是整个动画的初始化代码,其中我们利用了k3d的脚本库,所以你需要在项目中引用它,关于k3d,你可以在最后的源代码中找到它。

在今天的HTML教程里,我们要学习一下如何使用HTML5
Canvas实现一个超酷而又简单的网络画板功能。在这个教程中,我们可以选择笔刷的类型、笔刷的大小以及笔刷的颜色,当然作为画板还需要很多功能,这里只是最基本的绘制功能,大家可以自己实现类似矩形、椭圆等复杂元素的绘制。


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下面是一些鼠标事件,你可以拖动鼠标来让其旋转,具体代码如下:

你也可以再这里查看DEMO演示

function onloadHandler()  {     var canvas = document.getElementById('canvas');     canvas.width = window.innerWidth;     canvas.height = window.innerHeight;     var k3dmain = new K3D.Controller(canvas, true);          // generate 3D objects          var obj1 = new K3D.K3DObject();     with (obj1)     {        drawmode = "solid";        shademode = "lightsource";        sortmode = "unsorted";        addphi = -0.5;        abouty = -90;        perslevel = 1000;        init(           [{x:-80,y:180,z:0},{x:0,y:180,z:-80},{x:0,y:0,z:-80},{x:-80,y:20,z:0},{x:-50,y:150,z:-30},{x:0,y:150,z:-80},{x:0,y:130,z:-80},{x:-30,y:130,z:-50},{x:-28,y:110,z:-52},{x:0,y:110,z:-80},{x:0,y:90,z:-80},{x:-45,y:90,z:-35},{x:-44,y:80,z:-36},{x:-25,y:80,z:-55},{x:-22,y:66,z:-58},{x:0,y:60,z:-80},{x:0,y:40,z:-80},{x:-40,y:50,z:-40}],           [],           [{color:[227,76,38],vertices:[0,1,2,3,0]},{color:[235,235,235],vertices:[4,5,6,7,8,9,10,11,4]},{color:[235,235,235],vertices:[12,13,14,15,16,17,12]}]        );     }     k3dmain.addK3DObject(obj1);          var obj2 = new K3D.K3DObject();     with (obj2)     {        drawmode = "solid";        shademode = "lightsource";        sortmode = "unsorted";        addphi = -0.5;        abouty = -90;        perslevel = 1000;        init(           [{x:0,y:180,z:-80},{x:80,y:180,z:0},{x:80,y:20,z:0},{x:0,y:0,z:-80},{x:0,y:165,z:-80},{x:68,y:165,z:-12},{x:55,y:35,z:-25},{x:0,y:20,z:-80},{x:0,y:150,z:-80},{x:50,y:150,z:-30},{x:47,y:130,z:-33},{x:0,y:130,z:-80},{x:0,y:110,z:-80},{x:45,y:110,z:-35},{x:40,y:50,z:-40},{x:0,y:40,z:-80},{x:0,y:60,z:-80},{x:20,y:66,z:-60},{x:23,y:90,z:-57},{x:0,y:90,z:-80}],           [],           [{color:[227,76,38],vertices:[0,1,2,3,0]},{color:[240,101,41],vertices:[4,5,6,7,4]},{color:[235,235,235],vertices:[8,9,10,11,8]},{color:[235,235,235],vertices:[12,13,14,15,16,17,18,19,12]}]        );     }     k3dmain.addK3DObject(obj2);          var obj3 = new K3D.K3DObject();     with (obj3)     {        drawmode = "solid";        shademode = "lightsource";        sortmode = "unsorted";        addphi = -0.5;        abouty = -90;        perslevel = 1000;        init(           [{x:80,y:180,z:0},{x:0,y:180,z:80},{x:0,y:0,z:80},{x:80,y:20,z:0},{x:50,y:150,z:30},{x:0,y:150,z:80},{x:0,y:130,z:80},{x:30,y:130,z:50},{x:28,y:110,z:52},{x:0,y:110,z:80},{x:0,y:90,z:80},{x:45,y:90,z:35},{x:44,y:80,z:36},{x:25,y:80,z:55},{x:22,y:66,z:58},{x:0,y:60,z:80},{x:0,y:40,z:80},{x:40,y:50,z:40}],           [],           [{color:[227,76,38],vertices:[0,1,2,3,0]},{color:[235,235,235],vertices:[4,5,6,7,8,9,10,11,4]},{color:[235,235,235],vertices:[12,13,14,15,16,17,12]}]        );     }     k3dmain.addK3DObject(obj3);          var obj4 = new K3D.K3DObject();     with (obj4)     {        drawmode = "solid";        shademode = "lightsource";        sortmode = "unsorted";        addphi = -0.5;        abouty = -90;        perslevel = 1000;        init(           [{x:0,y:180,z:80},{x:-80,y:180,z:0},{x:-80,y:20,z:0},{x:0,y:0,z:80},{x:0,y:165,z:80},{x:-68,y:165,z:12},{x:-55,y:35,z:25},{x:0,y:20,z:80},{x:0,y:150,z:80},{x:-50,y:150,z:30},{x:-47,y:130,z:33},{x:0,y:130,z:80},{x:0,y:110,z:80},{x:-45,y:110,z:35},{x:-40,y:50,z:40},{x:0,y:40,z:80},{x:0,y:60,z:80},{x:-20,y:66,z:60},{x:-23,y:90,z:57},{x:0,y:90,z:80}],           [],           [{color:[227,76,38],vertices:[0,1,2,3,0]},{color:[240,101,41],vertices:[4,5,6,7,4]},{color:[235,235,235],vertices:[8,9,10,11,8]},{color:[235,235,235],vertices:[12,13,14,15,16,17,18,19,12]}]        );     }     k3dmain.addK3DObject(obj4);          var objBase = new K3D.K3DObject();     with (objBase)     {        drawmode = "solid";        shademode = "lightsource";        sortmode = "unsorted";        addphi = -0.5;        abouty = -90;        perslevel = 1000;        init(           [{x:0,y:0,z:-80},{x:-80,y:20,z:0},{x:0,y:0,z:80},{x:80,y:20,z:0}],           [],           [{color:[227,76,38],vertices:[0,2,1,0]},{color:[227,76,38],vertices:[0,3,2,0]}]        );     }     k3dmain.addK3DObject(objBase);          var objHtml = new K3D.K3DObject();     with (objHtml)     {        drawmode = "solid";        shademode = "lightsource";        //sortmode = "unsorted";        color = [64,64,64];        doublesided = true;        addphi = -0.5;        abouty = 100;        scale = 0.75;        perslevel = 1000;        init(           [{x:-80,y:40,z:0},{x:-70,y:40,z:0},{x:-70,y:30,z:0},{x:-60,y:30,z:0},{x:-60,y:40,z:0},{x:-50,y:40,z:0},{x:-50,y:10,z:0},{x:-60,y:10,z:0},{x:-60,y:20,z:0},{x:-70,y:20,z:0},{x:-70,y:10,z:0},{x:-80,y:10,z:0},{x:-40,y:40,z:0},{x:-10,y:40,z:0},{x:-10,y:30,z:0},{x:-20,y:30,z:0},{x:-20,y:10,z:0},{x:-30,y:10,z:0},{x:-30,y:30,z:0},{x:-40,y:30,z:0},{x:0,y:40,z:0},{x:10,y:40,z:0},{x:20,y:30,z:0},{x:30,y:40,z:0},{x:40,y:40,z:0},{x:40,y:10,z:0},{x:30,y:10,z:0},{x:30,y:30,z:0},{x:20,y:20,z:0},{x:10,y:30,z:0},{x:10,y:10,z:0},{x:0,y:10,z:0},{x:50,y:40,z:0},{x:60,y:40,z:0},{x:60,y:20,z:0},{x:80,y:20,z:0},{x:80,y:10,z:0},{x:50,y:10,z:0}],           [],           [{vertices:[0,1,2,3,4,5,6,7,8,9,10,11,0]},{vertices:[12,13,14,15,16,17,18,19,12]},{vertices:[20,21,22,23,24,25,26,27,28,29,30,31,20]},{vertices:[32,33,34,35,36,37,32]}]        );     }     k3dmain.addK3DObject(objHtml);          // add render loop callback     var ctx = canvas.getContext('2d');     var rotationOffset = 0;     var len = (canvas.height > canvas.width ? canvas.height : canvas.width) * 0.7;     k3dmain.clearBackground = false;     k3dmain.callback = function()     {        // manually clear bg - as we want to render some extra goodies        ctx.clearRect(0, 0, canvas.width, canvas.height);                // draw bg effect before K3D does its 3D rendering        ctx.save();        ctx.translate(canvas.width/2, canvas.height/2);        ctx.rotate(rotationOffset);                // first fill pass - outer rays        var RAYCOUNT = 24;        ctx.fillStyle = "#eee";        ctx.beginPath();        for (var i=0; i<RAYCOUNT; i++)        {           // rotate context           ctx.rotate(TWOPI / RAYCOUNT);           ctx.moveTo(0, 0);           ctx.lineTo(-20, len);           ctx.lineTo(20, len);        }        ctx.closePath();        ctx.fill();        // second fill pass - inner rays        ctx.fillStyle = "#fff";        ctx.beginPath();        for (var i=0; i<RAYCOUNT; i++)        {           // rotate context           ctx.rotate(TWOPI / RAYCOUNT);           ctx.moveTo(0, 0);           ctx.lineTo(-15, len);           ctx.lineTo(15, len);        }        ctx.closePath();        ctx.fill();        ctx.restore();        rotationOffset += 0.005;                // apply user interaction to rotation        for (var i=0, objs=k3dmain.objects; i<objs.length; i++)        {           objs[i].ophi += targetRotationX;        }                if (targetRotationX > -0.5) targetRotationX -= 0.05;        else if (targetRotationX < -0.55) targetRotationX += 0.05;        if (targetRotationX > -0.55 && targetRotationX < -0.5) targetRotationX = -0.5;     };          // start demo loop     k3dmain.paused = true;     setInterval(function(){k3dmain.tick()}, 1000/60);  }

下面我们来简单地分析一下实现这个HTML5网页画板的原理及代码,代码由HTML以及Javascript组成,主要还是Javascript代码。

下面我们来简单分析一下实现这款3D动画的过程及其部分核心代码,主要由HTML代码以及Javascript代码组成。

Javascript代码:

首先我们通过一组变量来定义画板的样式,以及一些数据的初始化:

var canvas;
var context;
var canvasWidth = 490;
var canvasHeight = 220;
var padding = 25;
var lineWidth = 8;
var colorPurple = "#cb3594";
var colorGreen = "#659b41";
var colorYellow = "#ffcf33";
var colorBrown = "#986928";
var outlineImage = new Image();
var crayonImage = new Image();
var markerImage = new Image();
var eraserImage = new Image();
var crayonBackgroundImage = new Image();
var markerBackgroundImage = new Image();
var eraserBackgroundImage = new Image();
var crayonTextureImage = new Image();
var clickX = new Array();
var clickY = new Array();
var clickColor = new Array();
var clickTool = new Array();
var clickSize = new Array();
var clickDrag = new Array();
var paint = false;
var curColor = colorPurple;
var curTool = "crayon";
var curSize = "normal";
var mediumStartX = 18;
var mediumStartY = 19;
var mediumImageWidth = 93;
var mediumImageHeight = 46;
var drawingAreaX = 111;
var drawingAreaY = 11;
var drawingAreaWidth = 267;
var drawingAreaHeight = 200;
var toolHotspotStartY = 23;
var toolHotspotHeight = 38;
var sizeHotspotStartY = 157;
var sizeHotspotHeight = 36;
var sizeHotspotWidthObject = new Object();
sizeHotspotWidthObject.huge = 39;
sizeHotspotWidthObject.large = 25;
sizeHotspotWidthObject.normal = 18;
sizeHotspotWidthObject.small = 16;
var totalLoadResources = 8;
var curLoadResNum = 0;

接下来开始准备画布,也就是初始化Canvas对象:

function prepareCanvas()
{
    // Create the canvas (Neccessary for IE because it doesn't know what a canvas element is)
    var canvasDiv = document.getElementById('canvasDiv');
    canvas = document.createElement('canvas');
    canvas.setAttribute('width', canvasWidth);
    canvas.setAttribute('height', canvasHeight);
    canvas.setAttribute('id', 'canvas');
    canvasDiv.appendChild(canvas);
    if(typeof G_vmlCanvasManager != 'undefined') {
        canvas = G_vmlCanvasManager.initElement(canvas);
    }
    context = canvas.getContext("2d"); // Grab the 2d canvas context
    // Note: The above code is a workaround for IE 8 and lower. Otherwise we could have used:
    //     context = document.getElementById('canvas').getContext("2d");

    // Load images
    // -----------
    crayonImage.onload = function() { resourceLoaded(); 
    };
    crayonImage.src = "images/crayon-outline.png";
    //context.drawImage(crayonImage, 0, 0, 100, 100);

    markerImage.onload = function() { resourceLoaded(); 
    };
    markerImage.src = "images/marker-outline.png";

    eraserImage.onload = function() { resourceLoaded(); 
    };
    eraserImage.src = "images/eraser-outline.png";    

    crayonBackgroundImage.onload = function() { resourceLoaded(); 
    };
    crayonBackgroundImage.src = "images/crayon-background.png";

    markerBackgroundImage.onload = function() { resourceLoaded(); 
    };
    markerBackgroundImage.src = "images/marker-background.png";

    eraserBackgroundImage.onload = function() { resourceLoaded(); 
    };
    eraserBackgroundImage.src = "images/eraser-background.png";

    crayonTextureImage.onload = function() { resourceLoaded(); 
    };
    crayonTextureImage.src = "images/crayon-texture.png";

    outlineImage.onload = function() { resourceLoaded(); 
    };
    outlineImage.src = "images/watermelon-duck-outline.png";

    // Add mouse events
    // ----------------
    $('#canvas').mousedown(function(e)
    {
        // Mouse down location
        var mouseX = e.pageX - this.offsetLeft;
        var mouseY = e.pageY - this.offsetTop;

        if(mouseX < drawingAreaX) // Left of the drawing area
        {
            if(mouseX > mediumStartX)
            {
                if(mouseY > mediumStartY && mouseY < mediumStartY + mediumImageHeight){
                    curColor = colorPurple;
                }else if(mouseY > mediumStartY + mediumImageHeight && mouseY < mediumStartY + mediumImageHeight * 2){
                    curColor = colorGreen;
                }else if(mouseY > mediumStartY + mediumImageHeight * 2 && mouseY < mediumStartY + mediumImageHeight * 3){
                    curColor = colorYellow;
                }else if(mouseY > mediumStartY + mediumImageHeight * 3 && mouseY < mediumStartY + mediumImageHeight * 4){
                    curColor = colorBrown;
                }
            }
        }
        else if(mouseX > drawingAreaX + drawingAreaWidth) // Right of the drawing area
        {
            if(mouseY > toolHotspotStartY)
            {
                if(mouseY > sizeHotspotStartY)
                {
                    var sizeHotspotStartX = drawingAreaX + drawingAreaWidth;
                    if(mouseY < sizeHotspotStartY + sizeHotspotHeight && mouseX > sizeHotspotStartX)
                    {
                        if(mouseX < sizeHotspotStartX + sizeHotspotWidthObject.huge){
                            curSize = "huge";
                        }else if(mouseX < sizeHotspotStartX + sizeHotspotWidthObject.large + sizeHotspotWidthObject.huge){
                            curSize = "large";
                        }else if(mouseX < sizeHotspotStartX + sizeHotspotWidthObject.normal + sizeHotspotWidthObject.large + sizeHotspotWidthObject.huge){
                            curSize = "normal";
                        }else if(mouseX < sizeHotspotStartX + sizeHotspotWidthObject.small + sizeHotspotWidthObject.normal + sizeHotspotWidthObject.large + sizeHotspotWidthObject.huge){
                            curSize = "small";                        
                        }
                    }
                }
                else
                {
                    if(mouseY < toolHotspotStartY + toolHotspotHeight){
                        curTool = "crayon";
                    }else if(mouseY < toolHotspotStartY + toolHotspotHeight * 2){
                        curTool = "marker";
                    }else if(mouseY < toolHotspotStartY + toolHotspotHeight * 3){
                        curTool = "eraser";
                    }
                }
            }
        }
        else if(mouseY > drawingAreaY && mouseY < drawingAreaY + drawingAreaHeight)
        {
            // Mouse click location on drawing area
        }
        paint = true;
        addClick(mouseX, mouseY, false);
        redraw();
    });

    $('#canvas').mousemove(function(e){
        if(paint==true){
            addClick(e.pageX - this.offsetLeft, e.pageY - this.offsetTop, true);
            redraw();
        }
    });

    $('#canvas').mouseup(function(e){
        paint = false;
          redraw();
    });

    $('#canvas').mouseleave(function(e){
        paint = false;
    });
}

看起来很复杂,前面主要是初始化canvas的背景图片,后面主要是初始化画笔事件,像click、mouseup、mouseleave等鼠标事件。

下面是draw的主要方法:

function redraw()
{
    // Make sure required resources are loaded before redrawing
    if(curLoadResNum < totalLoadResources){ return; }

    clearCanvas();

    var locX;
    var locY;
    if(curTool == "crayon")
    {
        // Draw the crayon tool background
        context.drawImage(crayonBackgroundImage, 0, 0, canvasWidth, canvasHeight);

        // Purple
        locX = (curColor == colorPurple) ? 18 : 52;
        locY = 19;

        context.beginPath();
        context.moveTo(locX + 41, locY + 11);
        context.lineTo(locX + 41, locY + 35);
        context.lineTo(locX + 29, locY + 35);
        context.lineTo(locX + 29, locY + 33);
        context.lineTo(locX + 11, locY + 27);
        context.lineTo(locX + 11, locY + 19);
        context.lineTo(locX + 29, locY + 13);
        context.lineTo(locX + 29, locY + 11);
        context.lineTo(locX + 41, locY + 11);
        context.closePath();
        context.fillStyle = colorPurple;
        context.fill();    

        if(curColor == colorPurple){
            context.drawImage(crayonImage, locX, locY, mediumImageWidth, mediumImageHeight);
        }else{
            context.drawImage(crayonImage, 0, 0, 59, mediumImageHeight, locX, locY, 59, mediumImageHeight);
        }

        // Green
        locX = (curColor == colorGreen) ? 18 : 52;
        locY += 46;

        context.beginPath();
        context.moveTo(locX + 41, locY + 11);
        context.lineTo(locX + 41, locY + 35);
        context.lineTo(locX + 29, locY + 35);
        context.lineTo(locX + 29, locY + 33);
        context.lineTo(locX + 11, locY + 27);
        context.lineTo(locX + 11, locY + 19);
        context.lineTo(locX + 29, locY + 13);
        context.lineTo(locX + 29, locY + 11);
        context.lineTo(locX + 41, locY + 11);
        context.closePath();
        context.fillStyle = colorGreen;
        context.fill();    

        if(curColor == colorGreen){
            context.drawImage(crayonImage, locX, locY, mediumImageWidth, mediumImageHeight);
        }else{
            context.drawImage(crayonImage, 0, 0, 59, mediumImageHeight, locX, locY, 59, mediumImageHeight);
        }

        // Yellow
        locX = (curColor == colorYellow) ? 18 : 52;
        locY += 46;

        context.beginPath();
        context.moveTo(locX + 41, locY + 11);
        context.lineTo(locX + 41, locY + 35);
        context.lineTo(locX + 29, locY + 35);
        context.lineTo(locX + 29, locY + 33);
        context.lineTo(locX + 11, locY + 27);
        context.lineTo(locX + 11, locY + 19);
        context.lineTo(locX + 29, locY + 13);
        context.lineTo(locX + 29, locY + 11);
        context.lineTo(locX + 41, locY + 11);
        context.closePath();
        context.fillStyle = colorYellow;
        context.fill();    

        if(curColor == colorYellow){
            context.drawImage(crayonImage, locX, locY, mediumImageWidth, mediumImageHeight);
        }else{
            context.drawImage(crayonImage, 0, 0, 59, mediumImageHeight, locX, locY, 59, mediumImageHeight);
        }

        // Yellow
        locX = (curColor == colorBrown) ? 18 : 52;
        locY += 46;

        context.beginPath();
        context.moveTo(locX + 41, locY + 11);
        context.lineTo(locX + 41, locY + 35);
        context.lineTo(locX + 29, locY + 35);
        context.lineTo(locX + 29, locY + 33);
        context.lineTo(locX + 11, locY + 27);
        context.lineTo(locX + 11, locY + 19);
        context.lineTo(locX + 29, locY + 13);
        context.lineTo(locX + 29, locY + 11);
        context.lineTo(locX + 41, locY + 11);
        context.closePath();
        context.fillStyle = colorBrown;
        context.fill();    

        if(curColor == colorBrown){
            context.drawImage(crayonImage, locX, locY, mediumImageWidth, mediumImageHeight);
        }else{
            context.drawImage(crayonImage, 0, 0, 59, mediumImageHeight, locX, locY, 59, mediumImageHeight);
        }
    }
    else if(curTool == "marker")
    {
        // Draw the marker tool background
        context.drawImage(markerBackgroundImage, 0, 0, canvasWidth, canvasHeight);

        // Purple
        locX = (curColor == colorPurple) ? 18 : 52;
        locY = 19;

        context.beginPath();
        context.moveTo(locX + 10, locY + 24);
        context.lineTo(locX + 10, locY + 24);
        context.lineTo(locX + 22, locY + 16);
        context.lineTo(locX + 22, locY + 31);
        context.closePath();
        context.fillStyle = colorPurple;
        context.fill();    

        if(curColor == colorPurple){
            context.drawImage(markerImage, locX, locY, mediumImageWidth, mediumImageHeight);
        }else{
            context.drawImage(markerImage, 0, 0, 59, mediumImageHeight, locX, locY, 59, mediumImageHeight);
        }

        // Green
        locX = (curColor == colorGreen) ? 18 : 52;
        locY += 46;

        context.beginPath();
        context.moveTo(locX + 10, locY + 24);
        context.lineTo(locX + 10, locY + 24);
        context.lineTo(locX + 22, locY + 16);
        context.lineTo(locX + 22, locY + 31);
        context.closePath();
        context.fillStyle = colorGreen;
        context.fill();    

        if(curColor == colorGreen){
            context.drawImage(markerImage, locX, locY, mediumImageWidth, mediumImageHeight);
        }else{
            context.drawImage(markerImage, 0, 0, 59, mediumImageHeight, locX, locY, 59, mediumImageHeight);
        }

        // Yellow
        locX = (curColor == colorYellow) ? 18 : 52;
        locY += 46;

        context.beginPath();
        context.moveTo(locX + 10, locY + 24);
        context.lineTo(locX + 10, locY + 24);
        context.lineTo(locX + 22, locY + 16);
        context.lineTo(locX + 22, locY + 31);
        context.closePath();
        context.fillStyle = colorYellow;
        context.fill();    

        if(curColor == colorYellow){
            context.drawImage(markerImage, locX, locY, mediumImageWidth, mediumImageHeight);
        }else{
            context.drawImage(markerImage, 0, 0, 59, mediumImageHeight, locX, locY, 59, mediumImageHeight);
        }

        // Yellow
        locX = (curColor == colorBrown) ? 18 : 52;
        locY += 46;

        context.beginPath();
        context.moveTo(locX + 10, locY + 24);
        context.lineTo(locX + 10, locY + 24);
        context.lineTo(locX + 22, locY + 16);
        context.lineTo(locX + 22, locY + 31);
        context.closePath();
        context.fillStyle = colorBrown;
        context.fill();    

        if(curColor == colorBrown){
            context.drawImage(markerImage, locX, locY, mediumImageWidth, mediumImageHeight);
        }else{
            context.drawImage(markerImage, 0, 0, 59, mediumImageHeight, locX, locY, 59, mediumImageHeight);
        }
    }
    else if(curTool == "eraser")
    {
        context.drawImage(eraserBackgroundImage, 0, 0, canvasWidth, canvasHeight);
        context.drawImage(eraserImage, 18, 19, mediumImageWidth, mediumImageHeight);    
    }else{
        alert("Error: Current Tool is undefined");
    }

    if(curSize == "small"){
        locX = 467;
    }else if(curSize == "normal"){
        locX = 450;
    }else if(curSize == "large"){
        locX = 428;
    }else if(curSize == "huge"){
        locX = 399;
    }
    locY = 189;
    context.beginPath();
    context.rect(locX, locY, 2, 12);
    context.closePath();
    context.fillStyle = '#333333';
    context.fill();    

    // Keep the drawing in the drawing area
    context.save();
    context.beginPath();
    context.rect(drawingAreaX, drawingAreaY, drawingAreaWidth, drawingAreaHeight);
    context.clip();

    var radius;
    var i = 0;
    for(; i < clickX.length; i++)
    {        
        if(clickSize[i] == "small"){
            radius = 2;
        }else if(clickSize[i] == "normal"){
            radius = 5;
        }else if(clickSize[i] == "large"){
            radius = 10;
        }else if(clickSize[i] == "huge"){
            radius = 20;
        }else{
            alert("Error: Radius is zero for click " + i);
            radius = 0;    
        }

        context.beginPath();
        if(clickDrag[i] && i){
            context.moveTo(clickX[i-1], clickY[i-1]);
        }else{
            context.moveTo(clickX[i], clickY[i]);
        }
        context.lineTo(clickX[i], clickY[i]);
        context.closePath();

        if(clickTool[i] == "eraser"){
            //context.globalCompositeOperation = "destination-out"; // To erase instead of draw over with white
            context.strokeStyle = 'white';
        }else{
            //context.globalCompositeOperation = "source-over";    // To erase instead of draw over with white
            context.strokeStyle = clickColor[i];
        }
        context.lineJoin = "round";
        context.lineWidth = radius;
        context.stroke();

    }
    //context.globalCompositeOperation = "source-over";// To erase instead of draw over with white
    context.restore();

    // Overlay a crayon texture (if the current tool is crayon)
    if(curTool == "crayon"){
        context.globalAlpha = 0.4; // No IE support
        context.drawImage(crayonTextureImage, 0, 0, canvasWidth, canvasHeight);
    }
    context.globalAlpha = 1; // No IE support

    // Draw the outline image
    context.drawImage(outlineImage, drawingAreaX, drawingAreaY, drawingAreaWidth, drawingAreaHeight);
}

其实HTML5说白了还是需要很多Javascript支持,不过Canvas非常不错,可以让你在上面自由地绘制图形和动画。这款基于HTML5
Canvas的网页画板就是一个很好的例子。源代码下载>>

function onDocumentMouseDown( event ) {        event.preventDefault();            document.addEventListener('mousemove', onDocumentMouseMove, false);      document.addEventListener('mouseup', onDocumentMouseUp, false);      document.addEventListener('mouseout', onDocumentMouseOut, false);            mouseXOnMouseDown = event.clientX - windowHalfX;      targetRotationOnMouseDownX = targetRotationX;      mouseYOnMouseDown = event.clientY - windowHalfY;      targetRotationOnMouseDownY = targetRotationY;  }    function onDocumentMouseMove( event )  {      mouseX = event.clientX - windowHalfX;      targetRotationX = targetRotationOnMouseDownX + (mouseX - mouseXOnMouseDown) * 0.02;      mouseY = event.clientY - windowHalfY;      targetRotationY = targetRotationOnMouseDownY + (mouseY - mouseYOnMouseDown) * 0.02;  }    function onDocumentMouseUp( event )  {      document.removeEventListener('mousemove', onDocumentMouseMove, false);      document.removeEventListener('mouseup', onDocumentMouseUp, false);      document.removeEventListener('mouseout', onDocumentMouseOut, false);  }    function onDocumentMouseOut( event )  {      document.removeEventListener('mousemove', onDocumentMouseMove, false);      document.removeEventListener('mouseup', onDocumentMouseUp, false);      document.removeEventListener('mouseout', onDocumentMouseOut, false);  }    function onDocumentTouchStart( event )  {      if (event.touches.length == 1)      {          event.preventDefault();            mouseXOnMouseDown = event.touches[0].pageX - windowHalfX;          targetRotationOnMouseDownX = targetRotationX;          mouseYOnMouseDown = event.touches[0].pageY - windowHalfY;          targetRotationOnMouseDownY = targetRotationY;      }  }
<canvas id="canvas" style="background-color:#ddd"></canvas>

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