圖片處理是C#程式開發中時常會涉及到的一個業務，除了圖像的上傳、保存以及下載等功能外，根據上傳的圖片生成一個縮略圖也是常見業務，在C#語言中，可以通過Image類提供的相關方法對圖片進行操作，如指定寬高對圖片進行縮放， 指定高寬裁減裁剪圖片、生成圖片水印等。 定義一個圖片處理工具類PicDeal，該 ...
圖片處理是C#程式開發中時常會涉及到的一個業務，除了圖像的上傳、保存以及下載等功能外，根據上傳的圖片生成一個縮略圖也是常見業務，在C#語言中，可以通過Image類提供的相關方法對圖片進行操作，如指定寬高對圖片進行縮放， 指定高寬裁減裁剪圖片、生成圖片水印等。
定義一個圖片處理工具類PicDeal，該類實現了生成縮略圖、在圖片上生成圖片水印等相應功能。具體的業務代碼如下：
/// <summary> /// 枚舉,生成縮略圖模式 /// </summary> public enum ThumbnailMod : byte { /// <summary> /// HW /// </summary> HW, /// <summary> /// W /// </summary> W, /// <summary> /// H /// </summary> H, /// <summary> /// Cut /// </summary> Cut }; /// <summary> /// 操作圖片類, 生成縮略圖,添加水印 /// </summary> public static class PicDeal { private static Hashtable htmimes = new Hashtable(); internal static readonly string AllowExt = ".jpe|.jpeg|.jpg|.png|.tif|.tiff|.bmp"; #region 生成縮略圖 /// <summary> /// 生成縮略圖 /// </summary> /// <param name="originalImagePath"></param> /// <param name="width"></param> /// <param name="height"></param> /// <param name="mode"></param> /// <returns></returns> public static bool MakeThumbnail(string originalImagePath, int width, int height, ThumbnailMod mode) { string thumbnailPath = originalImagePath.Substring(0, originalImagePath.LastIndexOf('.')) + "s.jpg"; 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 ThumbnailMod.HW://指定高寬縮放（可能變形） break; case ThumbnailMod.W://指定寬，高按比例 toheight = originalImage.Height * width / originalImage.Width; break; case ThumbnailMod.H://指定高，寬按比例 towidth = originalImage.Width * height / originalImage.Height; break; case ThumbnailMod.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; } //新建一個bmp圖片 Image bitmap = new Bitmap(towidth, toheight); //新建一個畫板 Graphics g = Graphics.FromImage(bitmap); //設置高質量插值法 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High; //設置高質量,低速度呈現平滑程度 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; //清空畫布並以透明背景色填充 g.Clear(System.Drawing.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); bool isok = false; try { //以jpg格式保存縮略圖 bitmap.Save(thumbnailPath, ImageFormat.Jpeg); isok = true; } catch (Exception) { thumbnailPath = originalImagePath; } finally { originalImage.Dispose(); bitmap.Dispose(); g.Dispose(); } return isok; } #endregion #region 在圖片上生成圖片水印 ///// <summary> ///// 在圖片上生成圖片水印 ///// </summary> ///// <param name="Path">原伺服器圖片路徑</param> ///// <param name="Path_syp">生成的帶圖片水印的圖片路徑</param> ///// <param name="Path_sypf">水印圖片路徑</param> /// <summary> /// 在圖片上生成圖片水印 /// </summary> /// <param name="Path">原伺服器圖片路徑</param> /// <param name="Path_sypf">水印圖片路徑</param> public static void AddWaterPic(string Path, string Path_sypf) { try { Image image = Image.FromFile(Path); Image copyImage = Image.FromFile(Path_sypf); Graphics g = Graphics.FromImage(image); g.DrawImage(copyImage, new System.Drawing.Rectangle(image.Width - copyImage.Width, image.Height - copyImage.Height, copyImage.Width, copyImage.Height), 0, 0, copyImage.Width, copyImage.Height, System.Drawing.GraphicsUnit.Pixel); g.Dispose(); image.Save(Path + ".temp"); image.Dispose(); System.IO.File.Delete(Path); File.Move(Path + ".temp", Path); } catch { } } #endregion /// <summary> /// 公共方法 /// </summary> private static void GetImgType() { htmimes[".jpe"] = "image/jpeg"; htmimes[".jpeg"] = "image/jpeg"; htmimes[".jpg"] = "image/jpeg"; htmimes[".png"] = "image/png"; htmimes[".tif"] = "image/tiff"; htmimes[".tiff"] = "image/tiff"; htmimes[".bmp"] = "image/bmp"; } #region 返回新圖片尺寸 /// <summary> /// 返回新圖片尺寸 /// </summary> /// <param name="width">原始寬</param> /// <param name="height">原始高</param> /// <param name="maxWidth">新圖片最大寬</param> /// <param name="maxHeight">新圖片最大高</param> /// <returns></returns> public static Size ResizeImage(int width, int height, int maxWidth, int maxHeight) { decimal MAX_WIDTH = (decimal)maxWidth; decimal MAX_HEIGHT = (decimal)maxHeight; decimal ASPECT_RATIO = MAX_WIDTH / MAX_HEIGHT; int newWidth, newHeight; decimal originalWidth = (decimal)width; decimal originalHeight = (decimal)height; if (originalWidth > MAX_WIDTH || originalHeight > MAX_HEIGHT) { decimal factor; // determine the largest factor if (originalWidth / originalHeight > ASPECT_RATIO) { factor = originalWidth / MAX_WIDTH; newWidth = Convert.ToInt32(originalWidth / factor); newHeight = Convert.ToInt32(originalHeight / factor); } else { factor = originalHeight / MAX_HEIGHT; newWidth = Convert.ToInt32(originalWidth / factor); newHeight = Convert.ToInt32(originalHeight / factor); } } else { newWidth = width; newHeight = height; } return new Size(newWidth, newHeight); } #endregion }
備註：原文轉載自C#生成圖片的縮略圖_IT技術小趣屋。
