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HTML5 Canvas实现360度全景方法

小云云asal: 2018-01-31 10:52:446329semak imbas

本文主要介绍HTML5 Canvas实现360度全景图的示例代码，小编觉得挺不错的，现在分享给大家，也给大家做个参考。一起跟随小编过来看看吧，希望能帮助到大家。

很多购物网站现在都支持360实物全景图像，可以360度任意选择查看样品，这样对购买者来说是一个很好的消费体验，网上有很多这样的插件都是基于jQuery实现的有收费的也有免费的，其实很好用的一个叫3deye.js的插件。该插件支持桌面与移动终端iOS与Android，它的demo程序：http://www.voidcanvas.com/demo/28823deye/

自己玩了玩这个Demo以后，照着它的思路，用HTML5 Canvas也实现了类似的功能。

所以先说一下它的360度全景图的原理

1. 首先需要对实物拍照，间隔是每张照片旋转15度，所以需要23张照片。
2.照片准备好了以后，尽量选择JPG格式，裁剪到适当大小。
3.JavaScript中预加载所有照片，可以配合进度条显示加载精度
4.创建/获取Canvas对象，加上鼠标监听事件，当鼠标左右移动时候，适度的绘制不同帧。大致的原理就是这样，简单吧！

实现代码：

<!DOCTYPE html>  
<html>  
<head>  
  <meta charset=utf-8">  
  <title>Full 360 degree View</title>  
  <script>  
        var ctx = null; // global variable 2d context  
        var frame = 1; // 23  
        var width = 0;  
        var height = 0;  
        var started = false;  
        var images = new Array();  
        var startedX = -1;  
      window.onload = function() {  
        var canvas = document.getElementById("fullview_canvas");  
        canvas.width = 440;// window.innerWidth;  
        canvas.height = 691;//window.innerHeight;  
        width = canvas.width;  
        height = canvas.height;  
        var bar = document.getElementById(&#39;loadProgressBar&#39;);  
        for(var i=1; i<24; i++)  
        {  
            bar.value = i;  
            if(i<10)  
            {  
                images[i] = new Image();  
                images[i].src = "0" + i + ".jpg";  
            }  
            else   
            {  
                images[i] = new Image();  
                images[i].src = i + ".jpg";  
            }  
        }  
        ctx = canvas.getContext("2d");  
          
        // mouse event  
        canvas.addEventListener("mousedown", doMouseDown, false);  
        canvas.addEventListener(&#39;mousemove&#39;, doMouseMove, false);  
        canvas.addEventListener(&#39;mouseup&#39;,   doMouseUp, false);  
        // loaded();  
          
        // frame = 1  
        frame = 1;  
        images[frame].onload = function() {  
            redraw();  
            bar.style.display = &#39;none&#39;;  
        }  
    }  
    function doMouseDown(event) {  
        var x = event.pageX;  
        var y = event.pageY;  
        var canvas = event.target;  
        var loc = getPointOnCanvas(canvas, x, y);  
        console.log("mouse down at point( x:" + loc.x + ", y:" + loc.y + ")");  
        startedX = loc.x;  
        started = true;  
    }  
      
    function doMouseMove(event) {  
        var x = event.pageX;  
        var y = event.pageY;  
        var canvas = event.target;  
        var loc = getPointOnCanvas(canvas, x, y);  
        if (started) {  
            var count = Math.floor(Math.abs((startedX - loc.x)/30));  
            var frameIndex = Math.floor((startedX - loc.x)/30);  
            while(count > 0)  
            {                 
                console.log("frameIndex = " + frameIndex);  
                count--;      
                if(frameIndex > 0)  
                {  
                    frameIndex--;  
                    frame++;  
                } else if(frameIndex < 0)  
                {  
                    frameIndex++;  
                    frame--;  
                }  
                else if(frameIndex == 0)  
                {  
                    break;  
                }  
                                  
                if(frame >= 24)  
                {  
                    frame = 1;  
                }  
                if(frame <= 0)  
                {  
                    frame = 23;  
                }  
                redraw();  
            }  
        }  
    }  
      
    function doMouseUp(event) {  
        console.log("mouse up now");  
        if (started) {  
            doMouseMove(event);  
            startedX = -1;  
            started = false;  
        }  
    }  
  
    function getPointOnCanvas(canvas, x, y) {  
        var bbox = canvas.getBoundingClientRect();  
        return { x: x - bbox.left * (canvas.width  / bbox.width),  
                y: y - bbox.top  * (canvas.height / bbox.height)  
                };  
    }  
      
    function loaded() {  
        setTimeout( update, 1000/8);  
    }  
    function redraw()  
    {  
        // var imageObj = document.createElement("img");  
        // var imageObj = new Image();  
        var imageObj = images[frame];  
        ctx.clearRect(0, 0, width, height)  
        ctx.drawImage(imageObj, 0, 0, width, height);  
    }  
    function update() {  
        redraw();  
        frame++;  
        if (frame >= 23) frame = 1;  
        setTimeout( update, 1000/8);  
    }  
  </script>  
</head>  
<body>  
<progress id="loadProgressBar" value="0" max="23"></progress>   
<canvas id="fullview_canvas"></canvas>  
<button onclick="loaded()">Auto Play</button>  
</body>  
</html>

Demo演示文件下载地址-> fullview_jb51.rar

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