Preview the image before uploading the image function, can improve the user experience of your website, let the user clear to upload the picture is not selected. This code without JS plug-in, pure JavaScript combined with HTML to achieve, is a very good example, more complete:
Example 1
| The code is as follows |
Copy Code |
| <! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 transitional//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">
<title> Local picture Preview </title>
<style type= "Text/css" >
#preview {width:100px;height:100px;border:1px solid #000; overflow:hidden;}
#imghead {filter:progid:DXImageTransform.Microsoft.AlphaImageLoader (sizingmethod=image);}
</style>
<script type= "Text/javascript" >
function Previewimage (file)
{
var maxwidth = 100;
var maxheight = 100;
var div = document.getElementById (' preview ');
if (File.files && file.files[0])
{
div.innerhtml = ' ';
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
{
var sfilter= ' Filter:progid:DXImageTransform.Microsoft.AlphaImageLoader (sizingmethod=scale,src= ";
File.select ();
var src = document.selection.createRange (). text;
div.innerhtml = ' ';
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;margin-left: "+rect.left+" 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>
<body>
<div id= "Preview" >
<!--no preview of the default image, get yourself a-->
</div>
<br/>
<input type= "File" onchange= "Previewimage (This)"/>
</body>
|
Example 2
| The code is as follows |
Copy Code |
| <! DOCTYPE HTML PUBLIC "-//W3C//DTD XHTML 1.0 transitional//en" "Http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd ">
<meta http-equiv= "Content-type" content= "text/html; Charset=utf-8 "/>
<title> Local picture Preview </title>
<style type= "Text/css" >
#preview {width:100px;height:100px;border:1px solid #000; overflow:hidden;}
#imghead {filter:progid:DXImageTransform.Microsoft.AlphaImageLoader (sizingmethod=image);}
</style>
<script type= "Text/javascript" >
function Previewimage (file)
{
var maxwidth = 100;
var maxheight = 100;
var div = document.getElementById (' preview ');
if (File.files && file.files[0])
{
div.innerhtml = ' ';
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
{
var sfilter= ' Filter:progid:DXImageTransform.Microsoft.AlphaImageLoader (sizingmethod=scale,src= ";
File.select ();
var src = document.selection.createRange (). text;
div.innerhtml = ' ';
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;margin-left: "+rect.left+" 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>
<body>
<div id= "Preview" >
</div>
<br/>
<input type= ' file ' onchange= ' Previewimage (This) "/>
</body>
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