由于上传图片功能，现在大多数都需要在本地实现预览，为了能够更好的让用户体验到效果，实现成品的证明，需要兼容好几种浏览器，所有通过各个例子整合了这个例子插件，兼容火狐、谷歌、ie8，其他的没有进行测试过
代码如下:
(function($){
jQuery.fn.extend({
uploadPreview: function(opts){
opts = jQuery.extend({
width: 0,
height: 0,
imgPreview: null,
imgType: ["gif", "jpeg", "jpg", "bmp", "png"],
callback: function(){ return false; }
}, opts || {});

var _self = this;
var _this = $(this);
var imgPreview = $(opts.imgPreview);
//设置样式
autoScaling = function(){
imgPreview.css({"margin-left": 0,"margin-top": 0,"width":opts.width,"height":opts.height});
imgPreview.show();
}
//file按钮出发事件
_this.change(function(){
if (this.value) {
if (!RegExp("\.(" + opts.imgType.join("|") + ")$", "i").test(this.value.toLowerCase())) {
alert("图片类型必须是" + opts.imgType.join("，") + "中的一种");
this.value = "";
return false;
}
if ($.browser.msie) {//判断ie
var path = $(this).val();
if (/"\w\W"/.test(path)) {
path = path.slice(1,-1);
}
imgPreview.attr("src",path);
imgPreview.css({"margin-left": 0,"margin-top": 0,"width":opts.width,"height":opts.height});
setTimeout("autoScaling()", 100);
}
else {
if ($.browser.version < 7) {
imgPreview.attr('src', this.files.item(0).getAsDataURL());
}
else {
oFReader = new FileReader(), rFilter = /^(?:image\/bmp|image\/cis\-cod|image\/gif|image\/ief|image\/jpeg|image\/jpeg|image\/jpeg|image\/pipeg|image\/png|image\/svg\+xml|image\/tiff|image\/x\-cmu\-raster|image\/x\-cmx|image\/x\-icon|image\/x\-portable\-anymap|image\/x\-portable\-bitmap|image\/x\-portable\-graymap|image\/x\-portable\-pixmap|image\/x\-rgb|image\/x\-xbitmap|image\/x\-xpixmap|image\/x\-xwindowdump)$/i;
oFReader.onload = function(oFREvent){
imgPreview.attr('src', oFREvent.target.result);
};
var oFile = this.files[0];
oFReader.readAsDataURL(oFile);
}
imgPreview.css({"margin-left": 0,"margin-top": 0,"width":opts.width,"height":opts.height});
setTimeout("autoScaling()", 100);
}
}
opts.callback();
});
}
});
})(jQuery);

二、调用方法
代码如下:
jQuery(function(){
jQuery("#idFile1").uploadPreview({
width: 100,
height: 100,
imgPreview: "#idImg1",
imgType: ["bmp", "gif", "png", "jpg"],
callback: function() {
ip1();
return false;
}
});
);