上传缩略图如何实现不变形？等比例缩放
目前上传图片和生成缩略图的代码：
//这是标题图片上传方法 if (image != null) { string year = DateTime.Now.Year.ToString(); string month = DateTime.Now.Month.ToString("00"); string day = DateTime.Now.Day.ToString("00"); string fileFolder = string.Concat("Upload/", year, "/", month, "/", day); string path = HostingEnvironment.MapPath("~/" + fileFolder); if (!Directory.Exists(path)) { //在Upload目录下创建了一个文件夹 Directory.CreateDirectory(path); } string imagename = image.FileName; string fileType = Path.GetExtension(image.FileName).ToLower(); if (fileType == ".jpeg" || fileType == ".jpg" || fileType == ".png" || fileType == ".gif") { Random ran = new Random(); string ename = DateTime.Now.ToString("yyyyMMddhhmmssfff") + ran.Next(9999); //上传后生成的图片名 string name = ename + fileType; image.SaveAs(Path.Combine(path, name)); string imageurl = string.Concat(HostingEnvironment.ApplicationVirtualPath, fileFolder, "/", name); //生成标题图片 //缩略图名 string thumbName = ename + "_500x200" + fileType; //缩略图绝对路径 string thumbPath = string.Concat(HostingEnvironment.ApplicationPhysicalPath, fileFolder, "/", thumbName); // 设置缩略图保存路径 FileStream stream = new FileStream(Path.GetFullPath(thumbPath), FileMode.OpenOrCreate); // 缩放上传的文件 Image OrigImage = Image.FromStream(image.InputStream); // 创建缩略图对象 Bitmap TempBitmap = new Bitmap(550, 200); // 创建缩略图画质 Graphics NewImage = Graphics.FromImage(TempBitmap); NewImage.CompositingQuality = CompositingQuality.HighQuality; NewImage.SmoothingMode = SmoothingMode.HighQuality; NewImage.InterpolationMode = InterpolationMode.HighQualityBicubic; // 创建Rectangle对象进行绘制 Rectangle imageRectangle = new Rectangle(0, 0, 550, 200); NewImage.DrawImage(OrigImage, imageRectangle); // 保存缩略图 TempBitmap.Save(stream, OrigImage.RawFormat); // 释放资源 NewImage.Dispose(); TempBitmap.Dispose(); OrigImage.Dispose(); stream.Close(); stream.Dispose(); newArticle.ImageUrl = imageurl; } }/// <summary>/// 获取一个图片按等比例缩小后的大小。/// </summary>/// <param name="maxWidth">需要缩小到的宽度</param>/// <param name="maxHeight">需要缩小到的高度</param>/// <param name="imageOriginalWidth">图片的原始宽度</param>/// <param name="imageOriginalHeight">图片的原始高度</param>/// <returns>返回图片按等比例缩小后的实际大小</returns>public static Size GetNewSize(int maxWidth, int maxHeight, int imageOriginalWidth, int imageOriginalHeight){ double w = 0.0; double h = 0.0; double sw = Convert.ToDouble(imageOriginalWidth); double sh = Convert.ToDouble(imageOriginalHeight); double mw = Convert.ToDouble(maxWidth); double mh = Convert.ToDouble(maxHeight); if (sw < mw && sh < mh) { w = sw; h = sh; } else if ((sw / sh) > (mw / mh)) { w = maxWidth; h = (w * sh) / sw; } else { h = maxHeight; w = (h * sw) / sh; } return new Size(Convert.ToInt32(w), Convert.ToInt32(h));}/// <summary>/// 对给定的一个图片（Image对象）生成一个指定大小的缩略图。/// </summary>/// <param name="originalImage">原始图片</param>/// <param name="thumMaxWidth">缩略图的宽度</param>/// <param name="thumMaxHeight">缩略图的高度</param>/// <returns>返回缩略图的Image对象</returns>public static System.Drawing.Image GetThumbNailImage(System.Drawing.Image originalImage, int thumMaxWidth, int thumMaxHeight){ Size thumRealSize = Size.Empty; System.Drawing.Image newImage = originalImage; Graphics graphics = null; try { thumRealSize = GetNewSize(thumMaxWidth, thumMaxHeight, originalImage.Width, originalImage.Height); newImage = new Bitmap(thumRealSize.Width, thumRealSize.Height); graphics = Graphics.FromImage(newImage); graphics.CompositingQuality = CompositingQuality.HighQuality; graphics.InterpolationMode = InterpolationMode.HighQualityBicubic; graphics.SmoothingMode = SmoothingMode.HighQuality; graphics.Clear(Color.Transparent); graphics.DrawImage(originalImage, new Rectangle(0, 0, thumRealSize.Width, thumRealSize.Height), new Rectangle(0, 0, originalImage.Width, originalImage.Height), GraphicsUnit.Pixel); } catch { } finally { if (graphics != null) { graphics.Dispose(); graphics = null; } } return newImage;}
[解决办法]
/// <summary> /// 根据源图片生成缩略图 /// </summary> /// <param name="imgPath_old">源图(大图)物理路径</param> /// <param name="imgPath_new">缩略图物理路径(生成的缩略图将保存到该物理位置)</param> /// <param name="width">缩略图宽度</param> /// <param name="height">缩略图高度</param> /// <param name="mode">缩略图缩放模式(取值"HW":指定高宽缩放,可能变形；取值"W":按指定宽度,高度按比例缩放；取值"H":按指定高度,宽度按比例缩放；取值"Cut":按指定高度和宽度裁剪,不变形)；取值"DB":等比缩放,以值较大的作为标准进行等比缩放</param> /// <param name="type">即将生成缩略图的文件的扩展名(仅限：JPG、GIF、PNG、BMP)</param> public static void MakeThumbnail(string imgPath_old, string imgPath_new, int width, int height, string mode, string imageType, int xx, int yy) { System.Drawing.Image img = System.Drawing.Image.FromFile(imgPath_old); int towidth = width; int toheight = height; int x = 0; int y = 0; int ow = img.Width; int oh = img.Height; switch (mode) { case "HW": //指定高宽压缩 if ((double)img.Width / (double)img.Height > (double)width / (double)height)//判断图形是什么形状 { towidth = width; toheight = img.Height * width / img.Width; } else if ((double)img.Width / (double)img.Height == (double)width / (double)height) { towidth = width; toheight = height; } else { toheight = height; towidth = img.Width * height / img.Height; } break; case "W": //指定宽，高按比例 toheight = img.Height * width / img.Width; break; case "H": //指定高，宽按比例 towidth = img.Width * height / img.Height; break; case "Cut": //指定高宽裁减（不变形） if ((double)img.Width / (double)img.Height > (double)towidth / (double)toheight) { oh = img.Height; ow = img.Height * towidth / toheight; y = yy; x = (img.Width - ow) / 2; } else { ow = img.Width; oh = img.Width * height / towidth; x = xx; y = (img.Height - oh) / 2; } break; case "DB": // 按值较大的进行等比缩放（不变形） if ((double)img.Width / (double)towidth < (double)img.Height / (double)toheight) { toheight = height; towidth = img.Width * height / img.Height; } else { towidth = width; toheight = img.Height * width / img.Width; } break; default: break; } //新建一个bmp图片 System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight); //新建一个画板 System.Drawing.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(System.Drawing.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(img, new System.Drawing.Rectangle(0, 0, towidth, toheight), new System.Drawing.Rectangle(x, y, ow, oh), System.Drawing.GraphicsUnit.Pixel); try { //以jpg格式保存缩略图 switch (imageType.ToLower()) { case "gif": img.Save(imgPath_new, ImageFormat.Jpeg);//生成缩略图 break; case "jpg": bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Jpeg); break; case "bmp": bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Bmp); break; case "png": bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Png); break; default: bitmap.Save(imgPath_new, System.Drawing.Imaging.ImageFormat.Jpeg); break; } ////保存缩略图 // bitmap.Save(imgPath_new); } catch (System.Exception e) { throw e; } finally { img.Dispose(); bitmap.Dispose(); g.Dispose(); } }