.net上传图片按比例自动缩小或放大

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace Common.Utility
{
/// <summary>
/// 上传图片按比例自动缩小或放大
/// </summary>
public class ImageBigOrSmall
{
//// <summary>

/// 按比例缩小图片，自动计算宽度

/// </summary>

/// <param name="strOldPic">源图文件名(包括路径)</param>

/// <param name="strNewPic">缩小后保存为文件名(包括路径)</param>

/// <param name="intHeight">缩小至高度</param>

public static void SmallPicWidth(string strOldPic, string strNewPic, int intHeight)
{

System.Drawing.Bitmap objPic, objNewPic;

try
{

objPic = new System.Drawing.Bitmap(strOldPic);

int intWidth = (intHeight / objPic.Height) * objPic.Width;

objNewPic = new System.Drawing.Bitmap(objPic, intWidth, intHeight);

objNewPic.Save(strNewPic);

}

catch (Exception exp) { throw exp; }

finally
{

objPic = null;

objNewPic = null;

}

}

/// <summary>

/// 按比例缩小图片，自动计算高度

/// </summary>

/// <param name="strOldPic">源图文件名(包括路径)</param>

/// <param name="strNewPic">缩小后保存为文件名(包括路径)</param>

/// <param name="intWidth">缩小至宽度</param>

public static void SmallPic(string strOldPic, string strNewPic, int intWidth)
{

System.Drawing.Bitmap objPic, objNewPic;

try
{

objPic = new System.Drawing.Bitmap(strOldPic);

int intHeight = (intWidth / objPic.Width) * objPic.Height;

objNewPic = new System.Drawing.Bitmap(objPic, intWidth, intHeight);

objNewPic.Save(strNewPic);

}

catch (Exception exp) { throw exp; }

finally
{

objPic = null;

objNewPic = null;

}

}

/**/
/// <summary>

/// 缩小图片

/// </summary>

/// <param name="strOldPic">源图文件名(包括路径)</param>

/// <param name="strNewPic">缩小后保存为文件名(包括路径)</param>

/// <param name="intWidth">缩小至宽度</param>

/// <param name="intHeight">缩小至高度</param>

public static void SmallPic(string strOldPic, string strNewPic, int intWidth, int intHeight)
{

System.Drawing.Bitmap objPic, objNewPic;

try
{

objPic = new System.Drawing.Bitmap(strOldPic);

objNewPic = new System.Drawing.Bitmap(objPic, intWidth, intHeight);

objNewPic.Save(strNewPic);

}

catch (Exception exp)

{ throw exp; }

finally
{

objPic = null;

objNewPic = null;

}

}

/*
以上两个方法注意：

1：当小于1大于0值转化为int型时值会为零，以至上方法中intWidth 为零，即出现Bitmap方法中参数无效现象，故以上方法仅供参考，还需自己数据类型转化；

2：当strOldPic与strNewPic值一致时，即用新大小图片替换旧图片时，原图片对象objPic 需释放，即：objPic.Dispose();

*/
}
}