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：獲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讀取照片的拍攝信息，詳見 http://code.ciaoca.com/javascript/exif-js/
這里主要用到Orientation屬性。
Orientation屬性說明如下：
| 旋轉角度 | 參數 |
| 0° | 1 |
| 順時針90° | 6 |
| 逆時針90° | 8 |
| 180° | 3 |
<!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/mobileBUGFix.mini.js" ></script> <script type="text/javascript" src="js/uploadPicture/uploadImage.js" ></script> <script type="text/javascript" src="js/exif.js" ></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>
自己寫的js：
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,請稍后...");
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;
//獲取照片方向角屬性，用戶旋轉控制
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;
}
alert(expectWidth+','+expectHeight);
var canvas = document.createElement("canvas");
var ctx = canvas.getContext("2d");
canvas.width = expectWidth;
canvas.height = expectHeight;
ctx.drawImage(this, 0, 0, expectWidth, expectHeight);
alert(canvas.width+','+canvas.height);
var base64 = null;
var mpImg = new MegaPixImage(image);
mpImg.render(canvas, {
maxWidth: 800,
maxHeight: 1200,
quality: 0.8,
orientation: Orientation
});
base64 = canvas.toDataURL("image/jpeg", 0.8);
//uploadImage(base64);
$("#myImage").attr("src", base64);
};
};
oReader.readAsDataURL(file);
}
}用到的第三方js文件：mobileBUGFix.mini.js
