/// <summary> /// 生成缩略图 /// </summary> /// <param name="originalImage">原图</param> /// <param name="thumbnailPath">缩略图路径(物理路径)</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</param> public static void MakeThumbnail(this Image originalImage, string thumbnailPath, int width, int height, ThumbnailCutMode mode) { int towidth = width; int toheight = height; int x = 0; int y = 0; int ow = originalImage.Width; int oh = originalImage.Height; switch (mode) { case ThumbnailCutMode.Fixed: //指定高宽缩放(可能变形) break; case ThumbnailCutMode.LockWidth: //指定宽,高按比例 toheight = originalImage.Height * width / originalImage.Width; break; case ThumbnailCutMode.LockHeight: //指定高,宽按比例 towidth = originalImage.Width * height / originalImage.Height; break; case ThumbnailCutMode.Cut: //指定高宽裁减(不变形) if (originalImage.Width / (double)originalImage.Height > 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; } //新建一个bmp图片 Image bitmap = new Bitmap(towidth, toheight); //新建一个画板 Graphics g = Graphics.FromImage(bitmap); //设置高质量插值法 g.InterpolationMode = InterpolationMode.High; //设置高质量,低速度呈现平滑程度 g.SmoothingMode = 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 //第一个:对哪张图片进行操作。 //二:画多么大。 //三:画那块区域。 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 bitmap.Save(thumbnailPath, ImageFormat.Jpeg); } finally { originalImage.Dispose(); bitmap.Dispose(); g.Dispose(); } }
/// <summary> /// 生成缩略图 /// </summary> /// <param name="originalImage">原图</param> /// <param name="thumbnailPath">缩略图路径(物理路径)</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</param> public static void MakeThumbnail(this Image originalImage, string thumbnailPath, int width, int height, ThumbnailCutMode mode) { using var bitmap = MakeThumbnail(originalImage, width, height, mode); bitmap.Save(thumbnailPath, originalImage.RawFormat); }
/// <summary> /// 生成缩略图 /// </summary> /// <param name="originalImage">原图</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</param> public static Image ThumbnailImage(this Image originalImage, int width, int height, ThumbnailCutMode mode = ThumbnailCutMode.Cut) { int towidth = width; int toheight = height; int x = 0; int y = 0; int ow = originalImage.Width; int oh = originalImage.Height; switch (mode) { case ThumbnailCutMode.Fixed: //指定高宽缩放(可能变形) break; case ThumbnailCutMode.LockWidth: //指定宽,高按比例 toheight = originalImage.Height * width / originalImage.Width; break; case ThumbnailCutMode.LockHeight: //指定高,宽按比例 towidth = originalImage.Width * height / originalImage.Height; break; case ThumbnailCutMode.Cut: //指定高宽裁减(不变形) if (originalImage.Width / (double)originalImage.Height > 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; } //新建一个bmp图片 Image bitmap = new Bitmap(towidth, toheight); //新建一个画板 Graphics g = Graphics.FromImage(bitmap); //设置高质量插值法 g.InterpolationMode = InterpolationMode.High; //设置高质量,低速度呈现平滑程度 g.SmoothingMode = 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 { return(bitmap); } catch (Exception e) { throw e; } finally { originalImage.Dispose(); g.Dispose(); } }
/// <summary> /// 生成缩略图 /// </summary> /// <param name="originalFileName">原图文件</param> /// <param name="width">缩略图宽度</param> /// <param name="height">缩略图高度</param> /// <param name="thumbnailFileName">缩略图文件(物理路径)</param> /// <param name="mode">生成缩略图的方式</param> public static void MakeThumbnail(string originalFileName, int width, int height, string thumbnailFileName = "", ThumbnailCutMode mode = ThumbnailCutMode.Cut) { Image originalImage = Image.FromFile(originalFileName); string ext = Path.GetExtension(originalFileName); if (thumbnailFileName == "") { thumbnailFileName = originalFileName.Replace(ext, "_thumb" + ext); //没有指定缩略图文件名,原文件名后面跟上_thumb } originalImage.ThumbnailImage(width, height, mode).Save(thumbnailFileName); }