在html中，input标签type=file选择文件，转成base64编码，附上demo：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<meta name="viewport" content="width=device-width,initial-scale=1,maximum-scale=1,user-scalable=no">
<title></title>
</head>
<body>
<input type="file" class="uploading" name="file" id="uploadimg" accept="image/jpg,image/jpeg,image/gif,image/png">
<div style="width: 300px;height: 200px;text-align: center;">
<img id="img" style="max-width: 300px;max-height: 200px;"/>
</div>
</body>
<script src="js/jquery-3.1.1.min.js"></script>
<script>
function _addImgFileListener(obj, fun) {
$(obj).change(function() {
try {
var file = this.files[0];
var reader = new FileReader();
reader.onload = function() {
var img = new Image();
img.src = reader.result;
img.onload = function() {
var w = img.width,
h = img.height;
var canvas = document.createElement('canvas');
var ctx = canvas.getContext('2d');
$(canvas).attr({
width: w,
height: h
});
ctx.drawImage(img, 0, 0, w, h);
var base64 = canvas.toDataURL('image/jpeg', 0.5);
var result = {
url: window.URL.createObjectURL(file),
base64: base64,
clearBase64: base64.substr(base64.indexOf(',') + 1),
suffix: base64.substring(base64.indexOf('/') + 1, base64.indexOf(';')),
};
fun(result);
}
}
reader.readAsDataURL(this.files[0]);
} catch(e) {
_showMsg(e);
}
});
}
$(document).ready(function() {
_addImgFileListener("#uploadimg", function(data) {
//你的业务
console.log(data.base64)
$("#img").attr("src",data.base64);
});
})
</script>
</html>