演示地址：https://xibushijie.github.io/static/uploadImg.html
<!DOCTYPE> <html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><title>图片上传本地预览</title><style type="text/css">#preview {width: 260px;height: 190px;border: 1px solid #000;overflow: hidden;}#imghead {filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);}</style><script type="text/javascript">//图片上传预览 IE是用了滤镜。function previewImage(file) {var MAXWIDTH = 260;var MAXHEIGHT = 180;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;// img.style.marginLeft = rect.left+'px'; img.style.marginTop = rect.top + 'px';}var reader = new FileReader();reader.onload = function (evt) { img.src = evt.target.result; }reader.readAsDataURL(file.files[0]);}else //兼容IE {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:' + rect.top + ',' + rect.left + ',' + rect.width + ',' + rect.height);div.innerHTML = "<div id=divhead style='width:" + rect.width + "px;height:" + rect.height + "px;margin-top:" + rect.top + "px;" + sFilter + src + "\"'></div>";}}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;}</script> </head><body><div id="preview"><img id="imghead" width=100% height=auto border=0 src='a1.png'></div><input type="file" onchange="previewImage(this)" /> </body></html>
