用C#輕松在DOTNET中實(shí)現(xiàn)縮略圖

2010-08-28 10:44:50來源：西部e網(wǎng)作者：

以前，在頁(yè)面上實(shí)現(xiàn)縮略圖必須借助第三方組件。現(xiàn)在，有了.NET，就可以很輕松地實(shí)現(xiàn)縮略圖。下面就是實(shí)現(xiàn)縮略圖的例子。

ToThumbnailImage.aspx

<%@ Page language="c#" Codebehind="ToThumbnailImage.aspx.cs" Src="ToThumbnailImage.aspx.cs" AutoEventWireup="false" Inherits="Exam_C.ToThumbnailImage" %> <html> <head> <title>Lion互動(dòng)網(wǎng)絡(luò) =>生成縮略圖</title> </head> <body> <form id="Form1" method="post" runat="server"> </form> </body> </html>

ToThumbnailImage.aspx.cs

using System; using System.Collections; using System.ComponentModel; using System.Data; using System.Drawing; using System.Web; using System.Web.SessionState; using System.Web.UI; using System.Web.UI.WebControls; using System.Web.UI.HtmlControls; using System.Drawing.Imaging; namespace Exam_C { /// <summary> /// ToThumbnailImage 的摘要說明。 /// </summary> public class ToThumbnailImage : System.Web.UI.Page { /* Create By lion 2003-05-20 19:00 Copyright (C) 2004 www.LionSky.Net. All rights reserved. Web: http://www.Lionsky.net ; Email: lion-a@sohu.com */ static Hashtable htmimes=new Hashtable(); internal readonly string AllowExt = ".jpe|.jpeg|.jpg|.png|.tif|.tiff|.bmp"; #region Web 窗體設(shè)計(jì)器生成的代碼 override protected void OnInit(EventArgs e) { #region htmimes[".jpe"]="image/jpeg"; htmimes[".jpeg"]="image/jpeg"; htmimes[".jpg"]="image/jpeg"; htmimes[".png"]="image/png"; htmimes[".tif"]="image/tiff"; htmimes[".tiff"]="image/tiff"; htmimes[".bmp"]="image/bmp"; #endregion //調(diào)用生成縮略圖方法 ToThumbnailImages("lionsky.jpg","b.gif",300); } #endregion #region Helper /// <summary> /// 獲取圖像編碼解碼器的所有相關(guān)信息 /// </summary> /// <param name="mimeType">包含編碼解碼器的多用途網(wǎng)際郵件擴(kuò)充協(xié)議 (MIME) 類型的字符串</param> /// <returns>返回圖像編碼解碼器的所有相關(guān)信息</returns> static ImageCodecInfo GetCodecInfo(string mimeType) { ImageCodecInfo[] CodecInfo = ImageCodecInfo.GetImageEncoders(); foreach(ImageCodecInfo ici in CodecInfo) { if(ici.MimeType == mimeType)return ici; } return null; } /// <summary> /// 檢測(cè)擴(kuò)展名的有效性 /// </summary> /// <param name="sExt">文件名擴(kuò)展名</param> /// <returns>如果擴(kuò)展名有效,返回true,否則返回false.</returns> bool CheckValidExt(string sExt) { bool flag=false; string[] aExt = AllowExt.Split('|'); foreach(string filetype in aExt) { if(filetype.ToLower()==sExt) { flag = true; break; } } return flag; } /// <summary> /// 保存圖片 /// </summary> /// <param name="image">Image 對(duì)象</param> /// <param name="savePath">保存路徑</param> /// <param name="ici">指定格式的編解碼參數(shù)</param> void SaveImage(System.Drawing.Image image,string savePath,ImageCodecInfo ici) { //設(shè)置原圖片對(duì)象的 EncoderParameters 對(duì)象 EncoderParameters parameters = new EncoderParameters(1); parameters.Param[0] = new EncoderParameter(Encoder.Quality, ((long) 90)); image.Save(savePath, ici, parameters); parameters.Dispose(); } #endregion #region Methods /// <summary> /// 生成縮略圖 /// </summary> /// <param name="sourceImagePath">原圖片路徑(相對(duì)路徑)</param> /// <param name="thumbnailImagePath">生成的縮略圖路徑,如果為空則保存為原圖片路徑(相對(duì)路徑)</param> /// <param name="thumbnailImageWidth">縮略圖的寬度（高度與按源圖片比例自動(dòng)生成）</param> public void ToThumbnailImages(string sourceImagePath,string thumbnailImagePath,int thumbnailImageWidth) { string SourceImagePath = sourceImagePath; string ThumbnailImagePath = thumbnailImagePath; int ThumbnailImageWidth = thumbnailImageWidth; string sExt = SourceImagePath.Substring(SourceImagePath.LastIndexOf(".")).ToLower(); if(SourceImagePath.ToString()==System.String.Empty) throw new NullReferenceException("SourceImagePath is null!"); if(!CheckValidExt(sExt)) { throw new ArgumentException("原圖片文件格式不正確,支持的格式有[ "+ AllowExt +" ]","SourceImagePath"); } //從原圖片創(chuàng)建 Image 對(duì)象 System.Drawing.Image image = System.Drawing.Image.FromFile(HttpContext.Current.Server.MapPath (SourceImagePath)); int num = ((ThumbnailImageWidth / 4) * 3); int width = image.Width; int height = image.Height; //計(jì)算圖片的比例 if ((((double) width) / ((double) height)) >= 1.3333333333333333f) { num = ((height * ThumbnailImageWidth) / width); } else { ThumbnailImageWidth = ((width * num) / height); } if ((ThumbnailImageWidth < 1) || (num < 1)) { return; } //用指定的大小和格式初始化 Bitmap 類的新實(shí)例 Bitmap bitmap = new Bitmap(ThumbnailImageWidth, num, PixelFormat.Format32bppArgb); //從指定的 Image 對(duì)象創(chuàng)建新 Graphics 對(duì)象 Graphics graphics = Graphics.FromImage(bitmap); //清除整個(gè)繪圖面并以透明背景色填充 graphics.Clear(Color.Transparent); //在指定位置并且按指定大小繪制原圖片對(duì)象 graphics.DrawImage(image, new Rectangle(0, 0, ThumbnailImageWidth, num)); image.Dispose(); try { //將此原圖片以指定格式并用指定的編解碼參數(shù)保存到指定文件 string savepath = (ThumbnailImagePath==null?SourceImagePath:ThumbnailImagePath); SaveImage(bitmap,HttpContext.Current.Server.MapPath(savepath),GetCodecInfo((string)htmimes [sExt])); } catch(System.Exception e) { throw e; } finally { bitmap.Dispose(); graphics.Dispose(); } } #endregion } }

關(guān)鍵詞：C#

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用C#輕松在DOTNET中實(shí)現(xiàn)縮略圖

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