HTML5 Canvas實(shí)現(xiàn)360度全景圖的示例代碼

發(fā)布時(shí)間：2018-01-29 16:49:29 作者：風(fēng)雨兼程之2017

本篇文章主要介紹了HTML5 Canvas實(shí)現(xiàn)360度全景圖的示例代碼，小編覺得挺不錯(cuò)的，現(xiàn)在分享給大家，也給大家做個(gè)參考。一起跟隨小編過來看看吧

很多購物網(wǎng)站現(xiàn)在都支持360實(shí)物全景圖像，可以360度任意選擇查看樣品，這樣對(duì)購買者來說是一個(gè)很好的消費(fèi)體驗(yàn)，網(wǎng)上有很多這樣的插件都是基于jQuery實(shí)現(xiàn)的有收費(fèi)的也有免費(fèi)的，其實(shí)很好用的一個(gè)叫3deye.js的插件。該插件支持桌面與移動(dòng)終端iOS與Android，它的demo程序：http://www.voidcanvas.com/demo/28823deye/

自己玩了玩這個(gè)Demo以后，照著它的思路，用HTML5 Canvas也實(shí)現(xiàn)了類似的功能。

所以先說一下它的360度全景圖的原理

1. 首先需要對(duì)實(shí)物拍照，間隔是每張照片旋轉(zhuǎn)15度，所以需要23張照片。
2.照片準(zhǔn)備好了以后，盡量選擇JPG格式，裁剪到適當(dāng)大小。
3.JavaScript中預(yù)加載所有照片，可以配合進(jìn)度條顯示加載精度
4.創(chuàng)建/獲取Canvas對(duì)象，加上鼠標(biāo)監(jiān)聽事件，當(dāng)鼠標(biāo)左右移動(dòng)時(shí)候，適度的繪制不同幀。大致的原理就是這樣，簡單吧！

實(shí)現(xiàn)代碼：

<!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('loadProgressBar');  
        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('mousemove', doMouseMove, false);  
        canvas.addEventListener('mouseup',   doMouseUp, false);  
        // loaded();  
          
        // frame = 1  
        frame = 1;  
        images[frame].onload = function() {  
            redraw();  
            bar.style.display = 'none';  
        }  
    }  
    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演示文件下載地址-> fullview_jb51.rar

以上就是本文的全部內(nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。