原生js上传 加预览 兼容ie

Posted 2020-08-07

前提条件： ie浏览器模式下，用户要允许ie默认的加载项；以下兼容ie的方法才会生效

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/*图片上传预览 IE是用了滤镜*/
function previewImage(file) {
var MAXWIDTH = 60;
var MAXHEIGHT = 60;
var div = document.getElementById(‘preview‘);
if (file.files && file.files[0]) {
div.innerhtml = ‘<img id=imghead>‘;
var img = document.getElementById(‘imghead‘);
img.onload = function () {
var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight);
img.width = rect.width;
img.height = rect.height;
};
var reader = new FileReader();
reader.onload = function (evt) {
img.src = evt.target.result;
};
reader.readAsDataURL(file.files[0]);
div.style.display = "inline-block";
} else {
var sFilter = ‘filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale,src="‘;
file.select();
var src = document.selection.createRange().text;
div.innerHTML = ‘<img id=imghead>‘;
var img = document.getElementById(‘imghead‘);
img.filters.item(‘DXImageTransform.Microsoft.AlphaImageLoader‘).src = src;
var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight);
status = (rect.left + ‘,‘ + rect.width + ‘,‘ + rect.height);
div.innerHTML = "<div id=divhead style=‘width:" + rect.width + "px;height:" + rect.height + "px;" + sFilter + src + "\"‘></div>";
div.style.display = "inline-block";
}
}

function clacImgZoomParam(maxWidth, maxHeight, width, height) {
var param = {top: 0, left: 0, width: width, height: height};
if (width > maxWidth || height > maxHeight) {
rateWidth = width / maxWidth;
rateHeight = height / maxHeight;

if (rateWidth > rateHeight) {
param.width = maxWidth;
param.height = Math.round(height / rateWidth);
} else {
param.width = Math.round(width / rateHeight);
param.height = maxHeight;
}
}

param.left = Math.round((maxWidth - param.width) / 2);
param.top = Math.round((maxHeight - param.height) / 2);
return param;
}