利用exif.js解决ios手机上传竖拍照片旋转90度问题
在进行移动端手机照片上传时，iOS手机上传竖拍照片逆时针旋转90度，横排则无此问题；安卓手机则没这个问题。
因此解决这个问题的思路是：获取到照片拍摄的方向角，对非横拍的iOS照片进行角度旋转修正。
利用exif.js读取照片的拍摄信息，详见：http://code.ciaoca.com/javascript/exif-js/
主要代码如下：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="initial-scale=1.0, maximum-scale=1.0, user-scalable=no" />
<title>图片上传</title>
<script type="text/javascript" src="js/jquery-1.8.3.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;">
上传图片:
<input type="file" accept="image/*" id="uploadImage" capture="camera" onchange="selectFileImage(this);" /> //调取手机摄像头的属性
</div>
<div style="margin-top: 10px;">
<img alt="preview" src="" id="myImage" width="180" />
</div>
</body>
</html>
<script>
$('#uploadImage').on('change',function(){
selectFileImage(this);
});
function selectFileImage(fileObj) {
var file = fileObj.files['0'];
//图片方向角 added by lzk
var Orientation = null;
if (file) {
console.log("正在上传,请稍后...");
var rFilter = /^(image\/jpeg|image\/png)$/i; // 检查图片格式
if (!rFilter.test(file.type)) {
console.log("请选择jpeg、png格式的图片");
return;
}
//获取照片方向角属性，用户旋转控制
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 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;
//如果方向角不为1
if(Orientation != "" && Orientation != 1){
console.log('旋转处理');
switch(Orientation){
case 6://需要顺时针（向左）90度旋转
console.log('需要顺时针（向左）90度旋转');
rotateImg(this,'left',canvas);
break;
case 8://需要逆时针（向右）90度旋转
console.log('需要顺时针（向右）90度旋转');
rotateImg(this,'right',canvas);
break;
case 3://需要180度旋转
console.log('需要180度旋转');
rotateImg(this,'right',canvas);
rotateImg(this,'right',canvas);
break;
}
}
base64 = canvas.toDataURL("image/jpeg", 0.8);
$("#myImage").attr("src", base64);
console.log("上传完成,请稍后...");
};
};
oReader.readAsDataURL(file);
}
}
//对图片旋转处理
function rotateImg(img, direction,canvas) {
//最小与最大旋转方向，图片旋转4次后回到原方向
var min_step = 0;
var max_step = 3;
if (img == null)return;
var height = img.height;
var width = img.width;
var step = 2;
if (step == null) {
step = min_step;
}
if (direction == 'right') {
step++;
//旋转到原位置，即超过最大值
step > max_step && (step = min_step);
} else {
step--;
step < min_step && (step = max_step);
}
//旋转角度以弧度值为参数
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;
}
}
</script>
