C#5種方式產生縮圖

using System;using System.Collections.Generic;using System.Linq;using System.Text;using System.Drawing;using System.IO;namespace MyTest{    class imgThumbnail    {        public enum mode        {            W,            H,            HW,            Cut,            MaxHW        }        public imgThumbnail()        {        }        /// <summary>        /// 產生縮圖        /// </summary>        /// <param name="originalImagePath">源圖路徑（實體路徑）</param>        /// <param name="thumbnailPath">縮圖路徑（實體路徑）</param>        /// <param name="width">縮圖寬度</param>        /// <param name="height">縮圖高度</param>        /// <param name="mode">產生縮圖的方式</param>            public static Image MakeThumbnail(string originalImagePath, int width, int height, mode m)        {            if (!File.Exists(originalImagePath))            {                return null;            }            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 (m)            {                case mode.MaxHW:                    if ((ow / width) > (ow / height))                    {                        towidth = width;                        toheight = (Int32)Math.Ceiling(Convert.ToDecimal((oh * towidth) / ow));                        if (toheight > height)                        {                            towidth = Convert.ToInt32(towidth * (Convert.ToDecimal(height) / toheight));                            toheight = height;                        }                    }                    else                    {                        toheight = height;                        towidth = (Convert.ToInt32(Math.Ceiling(Convert.ToDecimal(ow * toheight)) / oh));                        if (towidth > width)                        {                            toheight = Convert.ToInt32(toheight * Convert.ToDecimal(width) / towidth);                            towidth = width;                        }                    }                    break;                case mode.HW://指定高寬縮放（可能變形）                                    break;                case mode.W://指定寬，高按比例                                        toheight = originalImage.Height * width / originalImage.Width;                    break;                case mode.H://指定高，寬按比例                    towidth = originalImage.Width * height / originalImage.Height;                    break;                case mode.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;                    }                    break;                default:                    break;            }            towidth = towidth > ow ? ow : towidth;            toheight = toheight > oh ? oh : toheight;            if (toheight == 0 || towidth == 0)            {                return null;            }            //建立一個bmp圖片            Image bitmap = new System.Drawing.Bitmap(towidth, toheight);            //建立一個畫板            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;            //清空畫布並以透明背景色填充            g.Clear(Color.Transparent);            //在指定位置並且按指定大小繪製原圖片的指定部分            g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),                new Rectangle(x, y, ow, oh),                GraphicsUnit.Pixel);            try            {                return bitmap;                //以jpg格式儲存縮圖                //bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);            }            catch (System.Exception e)            {                return null;                throw e;            }            finally            {                originalImage.Dispose();                //bitmap.Dispose();                g.Dispose();            }        }    }}