HTML5+canvas進行移動端手機照片上傳時，發現iOS手機上傳豎拍照片會逆時針旋轉90度，橫拍照片無此問題；Android手機沒這個問題。
因此解決這個問題的思路是：擷取到照片拍攝的方向角，對非橫拍的ios照片進行角度旋轉修正。
利用exif.js讀取照片的拍攝資訊，這裡主要用到Orientation屬性。
Orientation屬性說明如下：
下面就直接上代碼了。
主要有html5頁面和一個js，樣本功能包含了圖片壓縮和旋轉。
自己寫的是uploadImage.js。
html5測試頁面如下：
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <meta name="viewport" content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no" /> <title>圖片上傳</title> <script type="text/javascript" src="js/jquery-1.8.3.js"></script> <script type="text/javascript" src="js/uploadPicture/uploadImage.js" ></script> <script type="text/javascript" src="js/exif.js" ></script> <script> </script> </head> <body> <div style="height: 50px; line-height: 50px;text-align: center;border-bottom: 1px solid #171E28;"> 上傳圖片: <input type="file" accept="image/*" id="uploadImage" capture="camera" onchange="selectFileImage(this);" /> </div> <div style="margin-top: 10px;"> <img alt="preview" src="" id="myImage"/> </div> </body> </html>
uploadImage.js如下：
function selectFileImage(fileObj) { var file = fileObj.files['0']; //圖片方向角 added by lzk var Orientation = null; if (file) { console.log("正在上傳,請稍後..."); var rFilter = /^(image\/jpeg|image\/png)$/i; // 檢查圖片格式 if (!rFilter.test(file.type)) { //showMyTips("請選擇jpeg、png格式的圖片", false); return; } // var URL = URL || webkitURL; //擷取照片方向角屬性，使用者旋轉控制 EXIF.getData(file, function() { // alert(EXIF.pretty(this)); EXIF.getAllTags(this); //alert(EXIF.getTag(this, 'Orientation')); Orientation = EXIF.getTag(this, 'Orientation'); //return; }); var oReader = new FileReader(); oReader.onload = function(e) { //var blob = URL.createObjectURL(file); //_compress(blob, file, basePath); var image = new Image(); image.src = e.target.result; image.onload = function() { var expectWidth = this.naturalWidth; var expectHeight = this.naturalHeight; if (this.naturalWidth > this.naturalHeight && this.naturalWidth > 800) { expectWidth = 800; expectHeight = expectWidth * this.naturalHeight / this.naturalWidth; } else if (this.naturalHeight > this.naturalWidth && this.naturalHeight > 1200) { expectHeight = 1200; expectWidth = expectHeight * this.naturalWidth / this.naturalHeight; } var canvas = document.createElement("canvas"); var ctx = canvas.getContext("2d"); canvas.width = expectWidth; canvas.height = expectHeight; ctx.drawImage(this, 0, 0, expectWidth, expectHeight); var base64 = null; //修複ios if (navigator.userAgent.match(/iphone/i)) { console.log('iphone'); //alert(expectWidth + ',' + expectHeight); //如果方向角不為1，都需要進行旋轉 added by lzk if(Orientation != "" && Orientation != 1){ alert('旋轉處理'); switch(Orientation){ case 6://需要順時針（向左）90度旋轉 alert('需要順時針（向左）90度旋轉'); rotateImg(this,'left',canvas); break; case 8://需要逆時針（向右）90度旋轉 alert('需要順時針（向右）90度旋轉'); rotateImg(this,'right',canvas); break; case 3://需要180度旋轉 alert('需要180度旋轉'); rotateImg(this,'right',canvas);//轉兩次 rotateImg(this,'right',canvas); break; } } /*var mpImg = new MegaPixImage(image); mpImg.render(canvas, { maxWidth: 800, maxHeight: 1200, quality: 0.8, orientation: 8 });*/ base64 = canvas.toDataURL("image/jpeg", 0.8); }else if (navigator.userAgent.match(/Android/i)) {// 修複android var encoder = new JPEGEncoder(); base64 = encoder.encode(ctx.getImageData(0, 0, expectWidth, expectHeight), 80); }else{ //alert(Orientation); if(Orientation != "" && Orientation != 1){ //alert('旋轉處理'); switch(Orientation){ case 6://需要順時針（向左）90度旋轉 alert('需要順時針（向左）90度旋轉'); rotateImg(this,'left',canvas); break; case 8://需要逆時針（向右）90度旋轉 alert('需要順時針（向右）90度旋轉'); rotateImg(this,'right',canvas); break; case 3://需要180度旋轉 alert('需要180度旋轉'); rotateImg(this,'right',canvas);//轉兩次 rotateImg(this,'right',canvas); break; } } base64 = canvas.toDataURL("image/jpeg", 0.8); } //uploadImage(base64); $("#myImage").attr("src", base64); }; }; oReader.readAsDataURL(file); } } //對圖片旋轉處理 added by lzk function rotateImg(img, direction,canvas) { //alert(img); //最小與最大旋轉方向，圖片旋轉4次後回到原方向 var min_step = 0; var max_step = 3; //var img = document.getElementById(pid); if (img == null)return; //img的高度和寬度不能在img元素隱藏後擷取，否則會出錯 var height = img.height; var width = img.width; //var step = img.getAttribute('step'); var step = 2; if (step == null) { step = min_step; } if (direction == 'right') { step++; //旋轉到原位置，即超過最大值 step > max_step && (step = min_step); } else { step--; step < min_step && (step = max_step); } //img.setAttribute('step', step); /*var canvas = document.getElementById('pic_' + pid); if (canvas == null) { img.style.display = 'none'; canvas = document.createElement('canvas'); canvas.setAttribute('id', 'pic_' + pid); img.parentNode.appendChild(canvas); } */ //旋轉角度以弧度值為參數 var degree = step * 90 * Math.PI / 180; var ctx = canvas.getContext('2d'); switch (step) { case 0: canvas.width = width; canvas.height = height; ctx.drawImage(img, 0, 0); break; case 1: canvas.width = height; canvas.height = width; ctx.rotate(degree); ctx.drawImage(img, 0, -height); break; case 2: canvas.width = width; canvas.height = height; ctx.rotate(degree); ctx.drawImage(img, -width, -height); break; case 3: canvas.width = height; canvas.height = width; ctx.rotate(degree); ctx.drawImage(img, -width, 0); break; } }
以上就是本文的全部內容，希望對大家的學習有所協助，也希望大家多多支援雲棲社區。
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