曾写过在前端把图片按比例压缩不失真上传服务器的前端和后台,可惜没有及时做总结保留代码,只记得js利用了base64位压缩和Exif.js进行图片处理,还有其中让我头疼的ios拍照上传后会倒置等诸多问题,当时也是在看了网上的各种代码后才有思路进行编写,希望留下一些大佬的代码在以后小弟我方便学习
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<div>
<img src="imgzip.jpg" alt="" width="350">
<img alt="" id="transform">
</div>
<script>
/**
* 图片压缩,默认同比例压缩
* @param {Object} path
* pc端传入的路径可以为相对路径,但是在移动端上必须传入的路径是照相图片储存的绝对路径
* @param {Object} obj
* obj 对象 有 width, height, quality(0-1)
* @param {Object} callback
* 回调函数有一个参数,base64的字符串数据
quality 图片缩放比例0-1 越大越清晰
*/
// 调用函数处理图片
dealImage("imgzip.jpeg", {
// 注意:在pc端可以用绝对路径或相对路径,移动端最好用绝对路径
// width: 1000,
quality: 0.5
}, function (base) {
document.getElementById("transform").src = base;
var mb = showSize(base);
})
function showSize(base64url) {
//获取base64图片大小,返回字节
var str = base64url.replace('data:image/png;base64,', '');
var equalIndex = str.indexOf('=');
if (str.indexOf('=') > 0) {
str = str.substring(0, equalIndex);
}
var strLength = str.length;
var fileLength = parseInt(strLength - (strLength / 8) * 2);
console.log("压缩后的图片size", fileLength + "B")
return fileLength;
}
function dealImage(path, obj, callback) {
var img = new Image();
img.src = path;
img.onload = function () {
var that = this;
var ext = path.substring(path.lastIndexOf(".") + 1).toLowerCase();
// 默认按比例压缩
var w = that.width,
h = that.height,
scale = w / h;
w = obj.width || w;
h = obj.height || (w / scale);
var quality = obj.quality; // 默认图片质量为0.7,可以为image/jpeg或image/webp类型的图片设置图片质量,取值0-1,超出则以默认值0.92替代
//生成canvas
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
// 创建属性节点
var anw = document.createAttribute("width");
anw.nodeValue = w;
var anh = document.createAttribute("height");
anh.nodeValue = h;
canvas.setAttributeNode(anw);
canvas.setAttributeNode(anh);
ctx.drawImage(that, 0, 0, w, h);
// 图像质量
if (obj.quality && obj.quality <= 1 && obj.quality > 0) {
quality = obj.quality;
}
// quality值越小,所绘制出的图像越模糊
console.log("tup", ext)
var base64 = canvas.toDataURL('image/jpeg', quality);
// 回调函数返回base64的值
callback(base64);
}
}
</script>
</body>
</html>
上传前不失真,有需要的去做按比例压缩(算法自己想)
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0° 参数1
顺时针90° 6
逆时针90° 8
180° 3
接下来的代码是大佬写的,我用于学习借鉴:
下面代码原链接:https://blog.csdn.net/linlzk/article/details/48654835
<!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/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;">
上传图片:
<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>
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 = 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
测试demo下载地址:
http://download.csdn.net/detail/linlzk/9127441
附上Exif.js说明
http://code.ciaoca.com/javascript/exif-js/