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  • C#生成缩略图

    using System;
    using System.Collections.Generic;
    using System.Text;
    using System.Drawing;

    namespace Common
    {
        public class ImageMes
        {
            /// <summary>
            /// 生成缩略图
            /// </summary>
            /// <param name="originalImagePath">源图路径</param>
            /// <param name="thumbnailPath">缩略图路径</param>
            /// <param name="width">缩略图宽度</param>
            /// <param name="height">缩略图高度</param>
            /// <param name="mode">生成缩略图的方式:HW指定高宽缩放(可能变形);W指定宽,高按比例 H指定高,宽按比例 Cut指定高宽裁减(不变形)</param>  
            /// <param name="mode">要缩略图保存的格式(gif,jpg,bmp,png) 为空或未知类型都视为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"://指定高宽缩放(可能变形)        
                        break;
                    case "W"://指定宽,高按比例          
                        toheight = originalImage.Height * width / originalImage.Width;
                        break;
                    case "H"://指定高,宽按比例
                        towidth = originalImage.Width * height / originalImage.Height;
                        break;
                    case "Cut"://指定高宽裁减(不变形)        
                        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;
                }
                //新建一个bmp图片
                Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

                //新建一个画板
                Graphics g = System.Drawing.Graphics.FromImage(bitmap);

                //设置高质量插值法
                g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

                //设置高质量,低速度呈现平滑程度
                g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

                //清空画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绘制原图片的指定部分
                g.DrawImage(originalImage, new Rectangle(0, 0, towidth, toheight),
                  new Rectangle(x, y, ow, oh),
                  GraphicsUnit.Pixel);

                try
                {
                    //以jpg格式保存缩略图
                    switch (imageType.ToLower())
                    {
                        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;
                        default:
                            bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
                            break;
                    }
                }
                catch (System.Exception e)
                {
                    throw e;
                }
                finally
                {
                    originalImage.Dispose();
                    bitmap.Dispose();
                    g.Dispose();
                }
            }
        }
    }

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  • 原文地址:https://www.cnblogs.com/linzheng/p/1847148.html
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