我做了一个可以上传前预览图片缩略图的的自定义控件，跪求可用分。

本帖最后由 net_lover 于 2011-04-12 13:07:45 编辑

可以的方法就是读取图片的字节流。生成个新图片。。上代码
这是个自定义控件
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Web;
using System.Web.UI;
using System.Web.UI.WebControls;
using Segdzw.Business;namespace Segdzw.Business
{
    [DefaultProperty("Text")]
    [ToolboxData("<{0}:ImagePreview runat=server></{0}:ImagePreview>")]
       public class ImagePreview : Control, INamingContainer
    {
        protected override void Render(HtmlTextWriter writer)
        {
            StringBuilder sb = new StringBuilder();
            sb.Append("<div id=\""+this.ClientID+"_div\" style=\"display:none\">加载中</div> \r");
            sb.Append("<input type=\"file\" id=\"" + this.ClientID + "_file\" name=\"" + this.ClientID + "_file\" onchange=\"GetPreview('"+this.ClientID+"');\"/>");
            string strJs = PageUtils.GetScriptsLink(new string[] { "jquery-1.4.2.min.js", "ajaxfileupload.js", "ImagePreview.js" });
            if (!Page.ClientScript.IsStartupScriptRegistered(this.GetType(), "ImagePreview"))
                Page.ClientScript.RegisterStartupScript(this.GetType(), "ImagePreview", strJs);
            writer.Write(sb.ToString());
            base.Render(writer);
        }
    }
}

<%@ Page Language="C#" AutoEventWireup="true" CodeFile="ImagePreview.aspx.cs" Inherits="ImagePreview" %>
<%@ Register Assembly="Segdzw.Business" Namespace="Segdzw.Business" TagPrefix="cc1" %>
<html xmlns="http://www.w3.org/1999/xhtml">
<head id="Head1" runat="server">
    <title>上传图片</title>
</head>
<body>
    <form id="form1" runat="server">
    <cc1:ImagePreview ID="ImagePreview1" runat="server">
    </cc1:ImagePreview>
    <cc1:ImagePreview ID="ImagePreview2" runat="server">
    </cc1:ImagePreview>
    <cc1:ImagePreview ID="ImagePreview3" runat="server">
    </cc1:ImagePreview>
    </form>
</body>
</html>

ImagePreview.jsvar bwType = "";
$(function() // 获取浏览器的类型
{
    if ($.browser.msie && ($.browser.version == "6.0") && !$.support.style)//或者用 if(document.all)
    {
        bwType = "ie6";
    }
    else if ($.browser.msie && ($.browser.version == "7.0"))
    {
        bwType = "ie7";
    }
    else if ($.browser.msie && ($.browser.version == "8.0"))
    {
        bwType = "ie8";
    }
    else if ($.browser.msie && ($.browser.version == "9.0"))
    {
        bwType = "ie9";
    }
    else
    {
        bwType = "not_ie";
    }});
function GetPreview(clientid)
{
    if (bwType == "ie6")
    {
        $("#"+clientid+"_div").html("<img src='" + $("#"+clientid+"_file").val() + "'>");
    }
    else
    {
        AjaxFileUpload(clientid);
    }
}
function AjaxFileUpload(cid)
{
    $("#" + cid + "_div").ajaxStart(function()
    {
        $(this).show();
    })
    $.ajaxFileUpload({
        url: "ImagePreview.ashx",
        secureuri: false,
        fileElementId: cid+"_file", //Input file id
        dataType: "json",
        success: function(data, status)
        {
            if (data.status == "success")
            {
                $("#" + cid + "_div").html("<img src='data:image/gif;base64," + data.msg + "'>");
            }
        },
        error: function(data, status, e)
        {
            alert(data + status + e);
        }    });
}

就是要预览。 boss的需求
ImagePreview.ashx：
<%@ WebHandler Language="c#" Class="File_WebHandler" Debug="true" %>using System;
using System.Web;
using System.IO;
using System.Drawing;
using System.Drawing.Imaging;public class File_WebHandler : IHttpHandler
{
    public void ProcessRequest(HttpContext context)
    {
        if (context.Request.Files.Count > 0)
        {
            HttpPostedFile file = context.Request.Files[0];
            string path="";
            if (file.ContentLength > 0 && file.ContentType.IndexOf("image/") >= 0)
            {
                int width = 200;
                int height = 200;
                try
                {
                    path = @"{status: 'success',msg: '" + Convert.ToBase64String(ResizeImg(file.InputStream, width, height).GetBuffer()) + @"'}";
                }
                catch (Exception)
                {                    path = @"{status: 'error',msg: '发生错误'}";
                }
                context.Response.Write(path);
            }
        }
    }    public MemoryStream ResizeImg(Stream ImgFile, int maxWidth, int maxHeight)
    {
        Image imgPhoto = Image.FromStream(ImgFile);

        decimal desiredRatio = Math.Min((decimal)maxWidth / imgPhoto.Width, (decimal)maxHeight / imgPhoto.Height);
        int iWidth = (int)(imgPhoto.Width * desiredRatio);
        int iHeight = (int)(imgPhoto.Height * desiredRatio);

        Bitmap bmPhoto = new Bitmap(iWidth, iHeight);        Graphics gbmPhoto = Graphics.FromImage(bmPhoto);
        gbmPhoto.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;
        gbmPhoto.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
        gbmPhoto.DrawImage(imgPhoto, new Rectangle(0, 0, iWidth, iHeight), new Rectangle(0, 0, imgPhoto.Width, imgPhoto.Height), GraphicsUnit.Pixel);        MemoryStream ms = new MemoryStream();
        bmPhoto.Save(ms, ImageFormat.Jpeg);        imgPhoto.Dispose();
        gbmPhoto.Dispose();
        bmPhoto.Dispose();        return ms;
    }    public bool IsReusable
    {
        get
        {
            return false;
        }
    }

}

ajaxfileupload.jsjQuery.extend({
    createUploadIframe: function(id, uri)
{
//create frame
            var frameId = 'jUploadFrame' + id;

            if(window.ActiveXObject) {
                var io = document.createElement('<iframe id="' + frameId + '" name="' + frameId + '" />');
                if(typeof uri== 'boolean'){
                    io.src = 'javascript:false';
                }
                else if(typeof uri== 'string'){
                    io.src = uri;
                }
            }
            else {
                var io = document.createElement('iframe');
                io.id = frameId;
                io.name = frameId;
            }
            io.style.position = 'absolute';
            io.style.top = '-1000px';
            io.style.left = '-1000px';            document.body.appendChild(io);            return io
    },
    createUploadForm: function(id, fileElementId)
{
//create form
var formId = 'jUploadForm' + id;
var fileId = 'jUploadFile' + id;
var form = $('<form  action="" method="POST" name="' + formId + '" id="' + formId + '" enctype="multipart/form-data"></form>');
var oldElement = $('#' + fileElementId);
var newElement = $(oldElement).clone();
$(oldElement).attr('id', fileId);
$(oldElement).before(newElement);
$(oldElement).appendTo(form);
//set attributes
$(form).css('position', 'absolute');
$(form).css('top', '-1200px');
$(form).css('left', '-1200px');
$(form).appendTo('body');
return form;
    },    ajaxFileUpload: function(s) {
        // TODO introduce global settings, allowing the client to modify them for all requests, not only timeout
        s = jQuery.extend({}, jQuery.ajaxSettings, s);
        var id = new Date().getTime()
var form = jQuery.createUploadForm(id, s.fileElementId);
var io = jQuery.createUploadIframe(id, s.secureuri);
var frameId = 'jUploadFrame' + id;
var formId = 'jUploadForm' + id;
        // Watch for a new set of requests
        if ( s.global && ! jQuery.active++ )
{
jQuery.event.trigger( "ajaxStart" );
}
        var requestDone = false;
        // Create the request object
        var xml = {}
        if ( s.global )
            jQuery.event.trigger("ajaxSend", [xml, s]);
        // Wait for a response to come back
        var uploadCallback = function(isTimeout)
{
var io = document.getElementById(frameId);
            try
{
if(io.contentWindow)
{
xml.responseText = io.contentWindow.document.body?io.contentWindow.document.body.innerHTML:null;
                 xml.responseXML = io.contentWindow.document.XMLDocument?io.contentWindow.document.XMLDocument:io.contentWindow.document;

}else if(io.contentDocument)
{
xml.responseText = io.contentDocument.document.body?io.contentDocument.document.body.innerHTML:null;
                 xml.responseXML = io.contentDocument.document.XMLDocument?io.contentDocument.document.XMLDocument:io.contentDocument.document;
}
            }catch(e)
{
jQuery.handleError(s, xml, null, e);
}
            if ( xml || isTimeout == "timeout")
{
                requestDone = true;
                var status;
                try {
                    status = isTimeout != "timeout" ? "success" : "error";
                    // Make sure that the request was successful or notmodified
                    if ( status != "error" )
{
                        // process the data (runs the xml through httpData regardless of callback)
                        var data = jQuery.uploadHttpData( xml, s.dataType );
                        // If a local callback was specified, fire it and pass it the data
                        if ( s.success )
                            s.success( data, status );

                        // Fire the global callback
                        if( s.global )
                            jQuery.event.trigger( "ajaxSuccess", [xml, s] );
                    } else
                        jQuery.handleError(s, xml, status);
                } catch(e)
{
                    status = "error";
                    jQuery.handleError(s, xml, status, e);
                }                // The request was completed
                if( s.global )
                    jQuery.event.trigger( "ajaxComplete", [xml, s] );                // Handle the global AJAX counter
                if ( s.global && ! --jQuery.active )
                    jQuery.event.trigger( "ajaxStop" );                // Process result
                if ( s.complete )
                    s.complete(xml, status);                jQuery(io).unbind()                setTimeout(function()
{ try
{
$(io).remove();
$(form).remove();

} catch(e)
{
jQuery.handleError(s, xml, null, e);
} }, 100)                xml = null            }
        }
        // Timeout checker
        if ( s.timeout > 0 )
{
            setTimeout(function(){
                // Check to see if the request is still happening
                if( !requestDone ) uploadCallback( "timeout" );
            }, s.timeout);
        }
        try
{
           // var io = $('#' + frameId);
var form = $('#' + formId);
$(form).attr('action', s.url);
$(form).attr('method', 'POST');
$(form).attr('target', frameId);
            if(form.encoding)
{
                form.encoding = 'multipart/form-data';
            }
            else
{
                form.enctype = 'multipart/form-data';
            }
            $(form).submit();        } catch(e)
{
            jQuery.handleError(s, xml, null, e);
        }
        if(window.attachEvent){
            document.getElementById(frameId).attachEvent('onload', uploadCallback);
        }
        else{
            document.getElementById(frameId).addEventListener('load', uploadCallback, false);
        }
        return {abort: function () {}};     },    uploadHttpData: function( r, type ) {
        var data = !type;
        data = type == "xml" || data ? r.responseXML : r.responseText;
        // If the type is "script", eval it in global context
        if ( type == "script" )
            jQuery.globalEval( data );
        // Get the JavaScript object, if JSON is used.
        if ( type == "json" )
            eval( "data = " + data );
        // evaluate scripts within html
        if ( type == "html" )
            jQuery("<div>").html(data).evalScripts();
//alert($('param', data).each(function(){alert($(this).attr('value'));}));
        return data;
    }
})

调试易

我做了一个可以上传前预览图片缩略图的的自定义控件，跪求可用分。

解决方案 »