C#生成縮略圖

using System;

using System.Collections.Generic;

using System.Text;

using System.Drawing;

namespace Common

{

public class ImageMes

/// <summary>

/// 生成縮略圖

/// </summary>

/// <param name="originalImagePath">源圖路徑</param>

/// <param name="thumbnailPath">縮略圖路徑</param>

/// <param name="width">縮略圖寬度</param>

/// <param name="height">縮略圖高度</param>

/// <param name="mode">生成縮略圖的方式:HW指定高寬縮放(可能變形);W指定寬，高按比例 H指定高，寬按比例 Cut指定高寬裁減(不變形)</param>　　

/// <param name="mode">要縮略圖儲存的格式(gif,jpg,bmp,png) 為空或未知類型都視為jpg</param>　　

public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode, string imageType)

Image originalImage = Image.FromFile(originalImagePath);

int towidth = width;

int toheight = height;

int x = 0;

int y = 0;

int ow = originalImage.Width;

int oh = originalImage.Height;

switch (mode)

case "HW"://指定高寬縮放（可能變形）　　　　　　　　

break;

case "W"://指定寬，高按比例　　　　　　　　　　

toheight = originalImage.Height * width / originalImage.Width;

case "H"://指定高，寬按比例

towidth = originalImage.Width * height / originalImage.Height;

case "Cut"://指定高寬裁減（不變形）　　　　　　　　

if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)

oh = originalImage.Height;

ow = originalImage.Height * towidth / toheight;

y = 0;

x = (originalImage.Width - ow) / 2;

}

else

ow = originalImage.Width;

oh = originalImage.Width * height / towidth;

x = 0;

y = (originalImage.Height - oh) / 2;

default:

//建立一個bmp圖檔

Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

//建立一個畫闆

Graphics g = System.Drawing.Graphics.FromImage(bitmap);

//設定高品質插值法

g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

//設定高品質,低速度呈現平滑程度

g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

//清空畫布并以透明背景色填充

g.Clear(Color.Transparent);

//在指定位置并且按指定大小繪制原圖檔的指定部分

g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),

new Rectangle(x, y, ow, oh),

GraphicsUnit.Pixel);

try

//以jpg格式儲存縮略圖

switch (imageType.ToLower())

case "gif":

bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif);

case "jpg":

bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);

case "bmp":

bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp);

case "png":

bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png);

catch (System.Exception e)

throw e;

finally

originalImage.Dispose();

bitmap.Dispose();

g.Dispose();

本文轉自linzheng 51CTO部落格，原文連結:http://blog.51cto.com/linzheng/1081742