html5+exif.js+canvas实现手机端照片上传预览、压缩、旋转功能

2021-12-17 前端-Html5

html5+canvas进行移动端手机照片上传时，发现ios手机上传竖拍照片会逆时针旋转90度，横拍照片无此问题；Android手机没这个问题。
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/
这里主要用到Orientation属性。
Orientation属性说明如下：

旋转角度	参数
0°	1
顺时针90°	6
逆时针90°	8
180°	3

html5页面：

[html]view plain copy print ?

图片上传 - 锐客网
上传图片:

文章图片

自己写的js：

[javascript]view plain copy print ?

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)) {
//showMyTips("请选择jpeg、png格式的图片", false);
return;
}
// var URL = URL || webkitURL;
//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 blob = URL.createObjectURL(file);
//_compress(blob, file, basePath);
var image = new Image();
image.src = https://www.it610.com/article/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);
}
}