这里有新鲜出炉的 Javascript 教程,程序狗速度看过来!
Javascript 是一种由 Netscape 的 LiveScript 发展而来的原型化继承的基于对象的动态类型的区分大小写的客户端脚本语言,主要目的是为了解决服务器端语言,比如 Perl,遗留的速度问题,为客户提供更流畅的浏览效果。
上传前预览使用 js 实现还是比较 cool 的,同时还可以兼容 IE 和 FF 的能做到这一点已经相当不容易了,下面与大家一起分享下具体的实现,感兴趣的你可不要错过了哈
效果图如下:
代码如下:
- <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
- <html xmlns="http://www.w3.org/1999/xhtml">
- <head>
- <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
- <title>
- 本地图片预览
- </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 = '<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 {
- 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;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>
- </head>
- <body>
- <div id="preview">
- <img id="imghead" width=100 height=100 border=0 src='../images/head01_big.jpg'>
- </div>
- <br/>
- <input type="file" onchange="previewImage(this)" />
- </body>
- </html>
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来源: http://www.phperz.com/article/17/0629/280119.html