DrawHelper.cs

using System;
using System.Data;
using System.Configuration;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Drawing;
using System.Drawing.Imaging;
using System.IO;

///

///DrawHelper 的摘要说明
///

public class DrawHelper
{
public DrawHelper()
{

}
//生成缩略图
public void CreateThumbnailImage(string sFileSrcPath, string sFileDstPath, int iSizeLimit)
{
//检测源图片是否存在
if (File.Exists(sFileSrcPath))
{
//获取源图片图像
System.Drawing.Image image = System.Drawing.Image.FromFile(sFileSrcPath);
//定义一个大小结构
SizeF size = new SizeF(image.Width, image.Height);
//计算出符合要求的大小
while (size.Width > iSizeLimit || size.Height > iSizeLimit)//51+aspx
{
size.Width /= 1.1F;
size.Height /= 1.1F;
}
//创建缩略图图像
Bitmap bitmap = new Bitmap(Convert.ToInt16(size.Width), Convert.ToInt16(size.Height));
//创建缩略图绘画面
Graphics g = Graphics.FromImage(bitmap);
//清除整个绘画面并以透明色填充
g.Clear(Color.Transparent);
//定义源图像矩形区域
Rectangle Srcrect = new Rectangle(0, 0, image.Width, image.Height);
//定义缩略图矩形区域
Rectangle Dstrect = new Rectangle(0, 0, bitmap.Width, bitmap.Height);
//绘制缩略图
g.DrawImage(bitmap, Dstrect, Srcrect, GraphicsUnit.Pixel);
//保存为Jpeg图片
bitmap.Save(sFileDstPath, ImageFormat.Jpeg);
//释放对象
g.Dispose();
image.Dispose();
bitmap.Dispose();

}
}
}