图片预览

<div class="return_right">
<div class="img_box">
<input type="button" value="上传" class="img_pointer"/>
<input type="file" name="upload1" id="upload1" class="up_btn" onchange="javascript:setImagePreview1(this);"/>
</div><img id="preview1" class="up_img"/>
<div class="img_box">
<input type="button" value="上传" class="img_pointer"/>
<input type="file" name="upload2" id="upload2" class="up_btn" onchange="javascript:setImagePreview2(this);"/>
</div><img id="preview2" class="up_img"/>
<div class="img_box">
<input type="button" value="上传" class="img_pointer"/>
<input type="file" name="upload3" id="upload3" class="up_btn" onchange="javascript:setImagePreview3(this);"/>
</div><img id="preview3" class="up_img"/>
</div>

function checkType(upload){
var image = document.getElementById(upload).value;
var extStart = image.lastIndexOf(".");
var ext = image.substring(extStart, image.length).toUpperCase();
if ( ext != ".PNG" && ext != ".GIF" && ext != ".JPG" && ext != ".JPEG") {
alert("图片限于png，gif，jpeg，jpg格式！");
return false;
}
return true;
}
function setImagePreview1(docObj) {
var imgObjPreview=document.getElementById("preview1");

if(docObj.files && docObj.files[0]){
try{
imgObjPreview.src = docObj.files[0].getAsDataURL();
}catch(e){
//火狐7以上版本不能用上面的getAsDataURL()方式获取，需要一下方式
imgObjPreview.src = window.URL.createObjectURL(docObj.files[0]);
}
}else{
//IE下，使用滤镜
docObj.select();
var imgSrc = document.selection.createRange().text;
//图片异常的捕捉，防止用户修改后缀来伪造图片
try{
imgObjPreview.style.filter="progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale)";
imgObjPreview.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;
}

document.selection.empty();
}

}

图片预览

原文：http://www.cnblogs.com/lanliying/p/5082298.html