生成缩略图是一个十分常用功能，找到了一个方法，重写部分代码，实用又好用，.net又一个生成缩略图的方法，不变形
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/// <summary> /// 为图片生成缩略图 /// </summary> /// <param name="phyPath">原图片的路径</param> /// <param name="width">缩略图宽</param> /// <param name="height">缩略图高</param> /// <returns></returns> public System.Drawing.Image GetHvtThumbnail(System.Drawing.Image image, int width, int height) { Bitmap m_hovertreeBmp = new Bitmap(width, height); //从Bitmap创建一个System.Drawing.Graphics Graphics m_HvtGr = Graphics.FromImage(m_hovertreeBmp); //设置 m_HvtGr.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; //下面这个也设成高质量 m_HvtGr.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality; //下面这个设成High m_HvtGr.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; //把原始图像绘制成上面所设置宽高的缩小图 Rectangle rectDestination = new Rectangle(0, 0, width, height); int m_width, m_height; if (image.Width * height > image.Height * width) { m_height = image.Height; m_width = (image.Height * width) / height; } else { m_width = image.Width; m_height = (image.Width * height) / width; } m_HvtGr.DrawImage(image, rectDestination, 0, 0, m_width, m_height, GraphicsUnit.Pixel); return m_hovertreeBmp; } |
C#缩略图生成类，采用高质量插值法实现缩略图生成，高质量,低速度呈现平滑程度，可以保持缩略图纵横比，在获取缩略图的时候一开始就根据百分比获取图片的尺寸、根据设定的大小返回图片的大小，并高质量保存缩略图图片，为原图片设置EncoderParameters 对象。
以下为类文件，建议保存文件名为：ImageHelper.cs
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using System;using System.Collections.Generic;using System.Drawing;using System.Drawing.Imaging;namespace HtmlSnap{ public static class ImageHelper { /// 获取缩略图 public static Image GetThumbnailImage(Image image, int width, int height) { if (image == null || width < 1 || height < 1) return null; // 新建一个bmp图片 Image bitmap = new System.Drawing.Bitmap(width, height); // 新建一个画板 using (Graphics g = System.Drawing.Graphics.FromImage(bitmap)) { // 设置高质量插值法 g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; // 设置高质量,低速度呈现平滑程度 g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; // 高质量、低速度复合 g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.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(image, new Rectangle(0, 0, width, height), new Rectangle(0, 0, image.Width, image.Height), GraphicsUnit.Pixel); return bitmap; } } /// <summary> /// 生成缩略图，并保持纵横比 /// </summary> /// <returns>生成缩略图后对象</returns> public static Image GetThumbnailImageKeepRatio(Image image, int width, int height) { Size imageSize = GetImageSize(image, width, height); return GetThumbnailImage(image, imageSize.Width, imageSize.Height); } /// <summary> /// 根据百分比获取图片的尺寸 /// </summary> public static Size GetImageSize(Image picture, int percent) { if (picture == null || percent < 1) return Size.Empty; int width = picture.Width * percent / 100; int height = picture.Height * percent / 100; return GetImageSize(picture, width, height); } /// <summary> /// 根据设定的大小返回图片的大小，考虑图片长宽的比例问题 /// </summary> public static Size GetImageSize(Image picture, int width, int height) { if (picture == null || width < 1 || height < 1) return Size.Empty; Size imageSize; imageSize = new Size(width, height); double heightRatio = (double)picture.Height / picture.Width; double widthRatio = (double)picture.Width / picture.Height; int desiredHeight = imageSize.Height; int desiredWidth = imageSize.Width; imageSize.Height = desiredHeight; if (widthRatio > 0) imageSize.Width = Convert.ToInt32(imageSize.Height * widthRatio); if (imageSize.Width > desiredWidth) { imageSize.Width = desiredWidth; imageSize.Height = Convert.ToInt32(imageSize.Width * heightRatio); } return imageSize; } /// <summary> /// 获取图像编码解码器的所有相关信息 /// </summary> /// <param name="mimeType">包含编码解码器的多用途网际邮件扩充协议 (MIME) 类型的字符串</param> /// <returns>返回图像编码解码器的所有相关信息</returns> public static ImageCodecInfo GetCodecInfo(string mimeType) { ImageCodecInfo[] CodecInfo = ImageCodecInfo.GetImageEncoders(); foreach (ImageCodecInfo ici in CodecInfo) { if (ici.MimeType == mimeType) return ici; } return null; } public static ImageCodecInfo GetImageCodecInfo(ImageFormat format) { ImageCodecInfo[] encoders = ImageCodecInfo.GetImageEncoders(); foreach (ImageCodecInfo icf in encoders) { if (icf.FormatID == format.Guid) { return icf; } } return null; } public static void SaveImage(Image image, string savePath, ImageFormat format) { SaveImage(image, savePath, GetImageCodecInfo(format)); } /// <summary> /// 高质量保存图片 /// </summary> private static void SaveImage(Image image, string savePath, ImageCodecInfo ici) { // 设置 原图片 对象的 EncoderParameters 对象 EncoderParameters parms = new EncoderParameters(1); EncoderParameter parm = new EncoderParameter(Encoder.Quality, ((long)95)); parms.Param[0] = parm; image.Save(savePath, ici, parms); parms.Dispose(); } }} |
