生成縮略圖

有一段時間，生成縮略圖一直困擾着我，當時，我還傻傻的用百度搜 “把大圖片轉換成小圖片”，未能找到。這個代碼是我參考了網上的代碼寫的一個類：

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

namespace 建立縮略圖
{
    class imgThumbnail
    {
        /// <summary>
        /// 生成縮略圖
        /// </summary>
        /// <param name="originalImagePath">源圖片路徑</param>
        /// <param name="thumbnailPath">縮略圖片保存的路徑</param>
        /// <param name="width">縮略圖寬</param>
        /// <param name="height">縮略圖高</param>
        public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height)
        {
            //獲取原始圖片
            System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);
            //縮略圖畫布寬高
            int towidth = width;
            int toheight = height;
            //原始圖片寫入畫布座標和寬高(用來設置裁減溢出部分)
            int x = 0;
            int y = 0;
            int ow = originalImage.Width;
            int oh = originalImage.Height;
            //原始圖片畫布,設置寫入縮略圖畫布座標和寬高(用來原始圖片整體寬高縮放)
            int bg_x = 0;
            int bg_y = 0;
            int bg_w = towidth;
            int bg_h = toheight;
            //倍數變量
            double multiple = 0;
            //獲取寬長的或是高長與縮略圖的倍數
            if (originalImage.Width >= originalImage.Height)
                multiple = (double)originalImage.Width / (double)width;
            else
                multiple = (double)originalImage.Height / (double)height;
            //上傳的圖片的寬和高小等於縮略圖
            if (ow <= width && oh <= height)
            {
                //縮略圖按原始寬高
                bg_w = originalImage.Width;
                bg_h = originalImage.Height;
                //空白部分用背景色填充
                bg_x = Convert.ToInt32(((double)towidth - (double)ow) / 2);
                bg_y = Convert.ToInt32(((double)toheight - (double)oh) / 2);
            }
            //上傳的圖片的寬和高大於縮略圖
            else
            {
                //寬高按比例縮放
                bg_w = Convert.ToInt32((double)originalImage.Width / multiple);
                bg_h = Convert.ToInt32((double)originalImage.Height / multiple);
                //空白部分用背景色填充
                bg_y = Convert.ToInt32(((double)height - (double)bg_h) / 2);
                bg_x = Convert.ToInt32(((double)width - (double)bg_w) / 2);
            }
            //新建一個bmp圖片,並設置縮略圖大小.
            System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);
            //新建一個畫板
            System.Drawing.Graphics g = System.Drawing.Graphics.FromImage(bitmap);
            //設置高質量插值法
            g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBilinear;
            //設置高質量,低速度呈現平滑程度
            g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;
            //清空畫布並設置背景色
            g.Clear(System.Drawing.ColorTranslator.FromHtml("#F2F2F2"));
            //在指定位置並且按指定大小繪製原圖片的指定部分
            //第一個System.Drawing.Rectangle是原圖片的畫布座標和寬高,第二個是原圖片寫在畫布上的座標和寬高,最後一個參數是指定數值單位爲像素
            g.DrawImage(originalImage, new System.Drawing.Rectangle(bg_x, bg_y, bg_w, bg_h), new System.Drawing.Rectangle(x, y, ow, oh), System.Drawing.GraphicsUnit.Pixel);
            try
            {
                //獲取圖片類型
                string fileExtension = System.IO.Path.GetExtension(originalImagePath).ToLower();
                //按原圖片類型保存縮略圖片,不按原格式圖片會出現模糊,鋸齒等問題.
                switch (fileExtension)
                {
                    case ".gif": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Gif); break;
                    case ".jpg": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg); break;
                    case ".bmp": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Bmp); break;
                    case ".png": bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Png); break;
                }
            }
            catch (System.Exception e)
            {
                throw e;
            }
            finally
            {
                originalImage.Dispose();
                bitmap.Dispose();
                g.Dispose();
            }
        }
    }
}

調用：

imgThumbnail.MakeThumbnail("C:\\Users\\Administrator\\Desktop\\js測試\\DSCF0949.JPG", "C:\\Users\\Administrator\\Desktop\\js測試\\1111.JPG",200,150);