javascript 上传图片前预览图片

   html

 

<div id="localImag"><img  id="preview" width="-1" height="-1" style="display:none" /></div>
<input type="file" id="file_head" onchange="javascript:setImagePreview();" />

   js

 

<script type="text/javascript">
	function setImagePreview() {
		var docObj = document.getElementById("file_head");
		var fileName = docObj.value;
		if (!fileName.match(/.jpg|.gif|.png|.bmp/i)) {
			alert('您上传的图片格式不正确，请重新选择！');
			return false;
		}

		var imgObjPreview = document.getElementById("preview");
		if (docObj.files && docObj.files[0]) {
			//火狐下，直接设img属性
			imgObjPreview.style.display = 'block';
			imgObjPreview.style.width = '63px';
			imgObjPreview.style.height = '63px';
			//imgObjPreview.src = docObj.files[0].getAsDataURL();
			if (window.navigator.userAgent.indexOf("Chrome") >= 1
					|| window.navigator.userAgent.indexOf("Safari") >= 1) {
				imgObjPreview.src = window.webkitURL
						.createObjectURL(docObj.files[0]);
			} else {
				imgObjPreview.src = window.URL.createObjectURL(docObj.files[0]);
			}
		} else {
			//IE下，使用滤镜
			docObj.select();
			docObj.blur();
			var imgSrc = document.selection.createRange().text;
			var localImagId = document.getElementById("localImag");
			//必须设置初始大小
			localImagId.style.width = "63px";
			localImagId.style.height = "63px";
			//图片异常的捕捉，防止用户修改后缀来伪造图片
			try {
				localImagId.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
				localImagId.filters
						.item("DXImageTransform.Microsoft.AlphaImageLoader").src = imgSrc;
			} catch (e) {
				alert("您上传的图片格式不正确，请重新选择！");
				return false;
			}
			imgObjPreview.style.display = 'none';
			document.selection.empty();
		}
		return true;
	}
</script>

 

   此js解决360浏览器显示图片问题。因为360浏览器6.2用的是Chrome的内核，而

 

window.URL.createObjectURL(docObj.files[0]);

 

   只有在火狐下才认得到，chrome中不认识window.URL.createObjectURL，所有用Safari的window.webkitURL.createObjectURL