js前端实现多图图片上传预览的两个方法
程序员文章站
2022-05-17 14:30:58
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一、将图片转成icon码的实现方式
html代码：
<div class="yanzRight">
<input style="margin-top:5px;float: left;" id="st18" name="evidence" onchange="previewImage(this,5)" type="file"/>
<span class="dui" id="imgOrder_dui" style="display: none;"></span>
</div>
<div id="preview5" style="margin-left:150px;clear:both; padding-top:15px;">
<img src="" alt="" id="imghead5" height="200" width="200" style="display:none;"/>
</div>
js代码
//图片预览功能
function previewImage(file,imgNum)
{
var MAXWIDTH = 200;
var MAXHEIGHT = 200;
var div = document.getElementById('preview'+imgNum);
if (file.files && file.files[0])
{
div.innerHTML ='<img id=imghead'+imgNum+'>';
var img = document.getElementById('imghead'+imgNum+'');
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 //
{
var sFilter='filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale,src="';
file.select();
var src = document.selection.createRange().text;
div.innerHTML = '<img id=imghead'+imgNum+'>';
var img = document.getElementById('imghead2');
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"+imgNum+" 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;
}
二、使用js的另一种方法一次选中多个图片预览展示
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>测试页面</title>
<script type="text/javascript">
//下面用于多图片上传预览功能
function setImagePreviews(avalue) {
var docObj = document.getElementById("doc");
var dd = document.getElementById("dd");
dd.innerHTML = "";
var fileList = docObj.files;
for (var i = 0; i < fileList.length; i++) {
dd.innerHTML += "<div style='float:left' > <img id='img" + i + "' /> </div>";
var imgObjPreview = document.getElementById("img"+i);
if (docObj.files && docObj.files[i]) {
//火狐下，直接设img属性
imgObjPreview.style.display = 'block';
imgObjPreview.style.width = '150px';
imgObjPreview.style.height = '180px';
//imgObjPreview.src = docObj.files[0].getAsDataURL();
//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[i]);
}
else {
//IE下，使用滤镜
docObj.select();
var imgSrc = document.selection.createRange().text;
alert(imgSrc)
var localImagId = document.getElementById("img" + i);
//必须设置初始大小
localImagId.style.width = "150px";
localImagId.style.height = "180px";
//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>
</head>
<body>
<div style="margin :0px auto; width:990px;">
<input type="file" name="file" id="doc" multiple="multiple" style="width:150px;" onchange="javascript:setImagePreviews();" accept="image/*" />
<div id="dd" style=" width:990px;"></div>
</div>
</body>
</html>