以前
在页面上实现缩略图必须借助第三方组件
现在
有了
NET
就可以很轻松地实现缩略图
下面就是实现缩略图的例子
关键字:C# ASPNET缩略图
实例下载:
ToThumbnailImageaspx
<%@ Page language=c# Codebehind=ToThumbnailImageaspxcs Src=ToThumbnailImageaspxcs AutoEventWireup=false Inherits=Exam_CToThumbnailImage %>
<html>
<head>
<title>Lion互动网络 =>生成缩略图</title>
</head>
<body>
<form id=Form method=post runat=server>
</form>
</body>
</html>
ToThumbnailImageaspxcs
using System;
using SystemCollections;
using SystemComponentModel;
using SystemData;
using SystemDrawing;
using SystemWeb;
using SystemWebSessionState;
using SystemWebUI;
using SystemWebUIWebControls;
using SystemWebUIHtmlControls;
using SystemDrawingImaging;
namespace Exam_C
{
/// <summary>
/// ToThumbnailImage 的摘要说明
/// </summary>
public class ToThumbnailImage : SystemWebUIPage
{
/*
Create By lion
:
Copyright (C) wwwLionSkyNet All rights reserved
Web: ;
Email:
*/
static Hashtable htmimes=new Hashtable();
internal readonly string AllowExt = jpe|jpeg|jpg|png|tif|tiff|bmp;
#region Web 窗体设计器生成的代码
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
//调用生成缩略图方法
ToThumbnailImages(lionskyjpgbgif);
}
#endregion
#region Helper
/// <summary>
/// 获取图像编码解码器的所有相关信息
/// </summary>
/// <param name=mimeType>包含编码解码器的多用途网际邮件扩充协议 (MIME) 类型的字符串</param>
/// <returns>返回图像编码解码器的所有相关信息</returns>
static ImageCodecInfo GetCodecInfo(string mimeType)
{
ImageCodecInfo[] CodecInfo = ImageCodecInfoGetImageEncoders();
foreach(ImageCodecInfo ici in CodecInfo)
{
if(iciMimeType == mimeType)return ici;
}
return null;
}
/// <summary>
/// 检测扩展名的有效性
/// </summary>
/// <param name=sExt>文件名扩展名</param>
/// <returns>如果扩展名有效返回true否则返回false</returns>
bool CheckValidExt(string sExt)
{
bool flag=false;
string[] aExt = AllowExtSplit(|);
foreach(string filetype in aExt)
{
if(filetypeToLower()==sExt)
{
flag = true;
break;
}
}
return flag;
}
/// <summary>
/// 保存图片
/// </summary>
/// <param name=image>Image 对象</param>
/// <param name=savePath>保存路径</param>
/// <param name=ici>指定格式的编解码参数</param>
void SaveImage(SystemDrawingImage imagestring savePathImageCodecInfo ici)
{
//设置 原图片 对象的 EncoderParameters 对象
EncoderParameters parameters = new EncoderParameters();
parametersParam[] = new EncoderParameter(EncoderQuality ((long) ));
imageSave(savePath ici parameters);
parametersDispose();
}
#endregion
#region Methods
/// <summary>
/// 生成缩略图
/// </summary>
/// <param name=sourceImagePath>原图片路径(相对路径)</param>
/// <param name=thumbnailImagePath>生成的缩略图路径如果为空则保存为原图片路径(相对路径)</param>
/// <param name=thumbnailImageWidth>缩略图的宽度（高度与按源图片比例自动生成）</param>
public void ToThumbnailImages(string sourceImagePathstring thumbnailImagePathint thumbnailImageWidth)
{
string SourceImagePath = sourceImagePath;
string ThumbnailImagePath = thumbnailImagePath;
int ThumbnailImageWidth = thumbnailImageWidth;
string sExt = SourceImagePathSubstring(SourceImagePathLastIndexOf())ToLower();
if(SourceImagePathToString()==SystemStringEmpty) throw new NullReferenceException(SourceImagePath is null!);
if(!CheckValidExt(sExt))
{
throw new ArgumentException(原图片文件格式不正确支持的格式有[ + AllowExt + ]SourceImagePath);
}
//从 原图片 创建 Image 对象
SystemDrawingImage image = SystemDrawingImageFromFile(HttpContextCurrentServerMapPath(SourceImagePath));
int num = ((ThumbnailImageWidth / ) * );
int width = imageWidth;
int height = imageHeight;
//计算图片的比例
if ((((double) width) / ((double) height)) >= f)
{
num = ((height * ThumbnailImageWidth) / width);
}
else
{
ThumbnailImageWidth = ((width * num) / height);
}
if ((ThumbnailImageWidth < ) || (num < ))
{
return;
}
//用指定的大小和格式初始化 Bitmap 类的新实例
Bitmap bitmap = new Bitmap(ThumbnailImageWidth num PixelFormatFormatbppArgb);
//从指定的 Image 对象创建新 Graphics 对象
Graphics graphics = GraphicsFromImage(bitmap);
//清除整个绘图面并以透明背景色填充
graphicsClear(ColorTransparent);
//在指定位置并且按指定大小绘制 原图片 对象
graphicsDrawImage(image new Rectangle( ThumbnailImageWidth num));
imageDispose();
try
{
//将此 原图片 以指定格式并用指定的编解码参数保存到指定文件
string savepath = (ThumbnailImagePath==null?SourceImagePath:ThumbnailImagePath);
SaveImage(bitmapHttpContextCurrentServerMapPath(savepath)GetCodecInfo((string)htmimes[sExt]));
}
catch(SystemException e)
{
throw e;
}
finally
{
bitmapDispose();
graphicsDispose();
}
}
#endregion
}
}
