C#压缩图片出现失真，就是颜色没有原图鲜艳
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悬赏园豆：180
[待解决问题]
代码:
/// <summary> /// 生成缩略图 /// </summary> /// <param name="img"></param> /// <param name="scale"></param> private Image Thumnail(Image img, int scale) { int h = (int)(img.Height * (scale / 100f)); int w = (int)(img.Width * (scale / 100f)); Bitmap thumbnailImage = new Bitmap(w, h); using (Graphics g = Graphics.FromImage(thumbnailImage)) { g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality; g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.HighQualityBicubic; g.CompositingQuality = System.Drawing.Drawing2D.CompositingQuality.HighQuality; g.DrawImage(img, new Rectangle(0, 0, w, h), new Rectangle(0, 0, img.Width, img.Height), GraphicsUnit.Pixel); } return thumbnailImage; }
求C#高质量压缩图片的算法！
所有回答(5)
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这是我经常使用的一种高质量算法，很不错的说
//求C#高质量压缩图片的算法！ public class ThumbnailMaker { //private static ThumbnailMaker instance; //public static ThumbnailMaker Instance //{ // get // { // lock (typeof(ThumbnailMaker)) // { // if (instance == null) // instance = new ThumbnailMaker(); // return instance; // } // } //} public static void CreateDirectory(string path) { if (path == "") return; string head = path.Substring(0, path.IndexOf("\\")); //d: string weibu = path.Substring(head.Length + 1); // \1\2 string hpath = head; while (weibu.IndexOf("\\") != -1) { string p = hpath + "\\" + weibu.Substring(0, weibu.IndexOf("\\")); hpath = p; if (!Directory.Exists(p)) Directory.CreateDirectory(p); int ix = weibu.IndexOf("\\") + 1; weibu = weibu.Substring(ix); } } /// <summary> /// 制作图片的缩略图 /// </summary> /// <param name="originalImage">原图</param> /// <param name="width">缩略图的宽（像素）</param> /// <param name="height">缩略图的高（像素）</param> /// <param name="mode">缩略方式</param> /// <returns>缩略图</returns> /// <remarks> /// <paramref name="mode"/>： /// <para>HW：指定的高宽缩放（可能变形）</para> /// <para>HWO：指定高宽缩放（可能变形）（过小则不变）</para> /// <para>W：指定宽，高按比例</para> /// <para>WO：指定宽（过小则不变），高按比例</para> /// <para>H：指定高，宽按比例</para> /// <para>HO：指定高（过小则不变），宽按比例</para> /// <para>CUT：指定高宽裁减（不变形）</para> /// </remarks> public static Image MakeThumbnail(Image originalImage, int width, int height, ThumbnailMode mode) { int towidth = width; int toheight = height; int x = 0; int y = 0; int ow = originalImage.Width; int oh = originalImage.Height; switch (mode) { case ThumbnailMode.UsrHeightWidth: //指定高宽缩放（可能变形） break; case ThumbnailMode.UsrHeightWidthBound: //指定高宽缩放（可能变形）（过小则不变） if (originalImage.Width <= width && originalImage.Height <= height) { return originalImage; } if (originalImage.Width < width) { towidth = originalImage.Width; } if (originalImage.Height < height) { toheight = originalImage.Height; } break; case ThumbnailMode.UsrWidth: //指定宽，高按比例 toheight = originalImage.Height * width / originalImage.Width; break; case ThumbnailMode.UsrWidthBound: //指定宽（过小则不变），高按比例 if (originalImage.Width <= width) { return originalImage; } else { toheight = originalImage.Height * width / originalImage.Width; } break; case ThumbnailMode.UsrHeight: //指定高，宽按比例 towidth = originalImage.Width * height / originalImage.Height; break; case ThumbnailMode.UsrHeightBound: //指定高（过小则不变），宽按比例 if (originalImage.Height <= height) { return originalImage; } else { towidth = originalImage.Width * height / originalImage.Height; } break; case ThumbnailMode.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 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.HighQualityBicubic; //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); g.Dispose(); return bitmap; } /// <summary> /// 制作图片的缩略图 /// </summary> /// <param name="originalStream">原图</param> /// <param name="thumbnailPath">保存缩略图的路径</param> /// <param name="width">缩略图的宽（像素）</param> /// <param name="height">缩略图的高（像素）</param> /// <param name="mode">缩略方式，参见<seealso cref="MakeThumbnail(Image, int, int, string)"/></param> public static void MakeThumbnail(Stream originalStream, string thumbnailPath, int width, int height, ThumbnailMode mode) { Image originalImage = Image.FromStream(originalStream); try { MakeThumbnail(originalImage, thumbnailPath, width, height, mode); } finally { originalImage.Dispose(); } } /// <summary> /// 制作图片的缩略图 /// </summary> /// <param name="originalImage">原图</param> /// <param name="thumbnailPath">保存缩略图的路径</param> /// <param name="width">缩略图的宽（像素）</param> /// <param name="height">缩略图的高（像素）</param> /// <param name="mode">缩略方式，参见<seealso cref="MakeThumbnail(Image, int, int, string)"/></param> public static void MakeThumbnail(Image originalImage, string thumbnailPath, int width, int height, ThumbnailMode mode) { Image bitmap = MakeThumbnail(originalImage, width, height, mode); try { //以jpg格式保存缩略图 bitmap.Save(thumbnailPath, ImageFormat.Jpeg); } finally { bitmap.Dispose(); } } /// <summary> /// 制作图片的缩略图 /// </summary> /// <param name="originalImagePath">原图的路径</param> /// <param name="thumbnailPath">保存缩略图的路径</param> /// <param name="width">缩略图的宽（像素）</param> /// <param name="height">缩略图的高（像素）</param> /// <param name="mode">缩略方式，参见<seealso cref="MakeThumbnail(Image, int, int, string)"/></param> public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, ThumbnailMode mode) { Image originalImage = Image.FromFile(originalImagePath); try { MakeThumbnail(originalImage, thumbnailPath, width, height, mode); } finally { originalImage.Dispose(); } } /// <summary> /// /// </summary> /// <param name="img"></param> /// <param name="width"></param> /// <param name="height"></param> /// <param name="mode"></param> public static byte[] MakeThumbnail(byte[] img, int width, int height, ThumbnailMode mode) { Stream byteStream = new MemoryStream(img); Image originalImage = Image.FromStream(byteStream); try { Image _img = MakeThumbnail(originalImage, width, height, mode); MemoryStream imgStream = new MemoryStream(); _img.Save(imgStream, ImageFormat.Jpeg); return imgStream.ToArray(); } finally { originalImage.Dispose(); } } /// <summary> /// 产生高清缩略图 固定大小 /// </summary> /// <param name="original_image_file">源文件</param> /// <param name="object_width">缩略图宽度</param> /// <param name="object_height">缩略图高度</param> public static void MakeHighQualityThumbnail(string original_image_file, string output, int object_width, int object_height) { int actual_width = 0; int actual_heigh = 0; string outputfilename = output; //original_image_file + ".jpg"; System.Drawing.Bitmap original_image = new Bitmap(original_image_file);//读取源文件 actual_width = original_image.Width; actual_heigh = original_image.Height; Bitmap img = new Bitmap(object_width, object_height); img.SetResolution(108f, 108f); Graphics gdiobj = Graphics.FromImage(img); gdiobj.CompositingQuality = CompositingQuality.HighQuality; gdiobj.SmoothingMode = SmoothingMode.HighQuality; gdiobj.InterpolationMode = InterpolationMode.HighQualityBicubic; gdiobj.PixelOffsetMode = PixelOffsetMode.HighQuality; gdiobj.FillRectangle(new SolidBrush(Color.White), 0, 0, object_width, object_height); Rectangle destrect = new Rectangle(0, 0, object_width, object_height); gdiobj.DrawImage(original_image, destrect, 0, 0, actual_width, actual_heigh, GraphicsUnit.Pixel); System.Drawing.Imaging.EncoderParameters ep = new System.Drawing.Imaging.EncoderParameters(1); ep.Param[0] = new System.Drawing.Imaging.EncoderParameter(System.Drawing.Imaging.Encoder.Quality, (long)100); System.Drawing.Imaging.ImageCodecInfo ici = System.Drawing.Imaging.ImageCodecInfo.GetImageEncoders()[0]; if (ici != null) { if (File.Exists(outputfilename)) File.Delete(outputfilename); img.Save(outputfilename, ici, ep); } else { img.Save(outputfilename, System.Drawing.Imaging.ImageFormat.Jpeg); } } /// <summary> /// /// </summary> /// <param name="img"></param> /// <param name="width"></param> /// <param name="height"></param> /// <param name="mode"></param> public static byte[] MakeThumbnail(byte[] img, int width, int height) { return MakeThumbnail(img, width, height, ThumbnailMode.UsrHeightBound); } } //<para>HW：指定的高宽缩放（可能变形）</para> //<para>HWO：指定高宽缩放（可能变形）（过小则不变）</para> //<para>W：指定宽，高按比例</para> //<para>WO：指定宽（过小则不变），高按比例</para> //<para>H：指定高，宽按比例</para> //<para>HO：指定高（过小则不变），宽按比例</para> //<para>CUT：指定高宽裁减（不变形）</para> public enum ThumbnailMode { UsrHeightWidth, UsrHeightWidthBound, UsrWidth, UsrWidthBound, UsrHeight, UsrHeightBound, Cut, NONE, }
调用示例：
ThumbnailMaker.MakeThumbnail("需要转换的图片名", 要保存的路径+ "\\"+Guid.NewGuid().ToString()+原图的扩展名, 宽, 高, ThumbnailMode.Cut);
抱歉，兄弟，你的代码和我上面粘出来的结果一样：颜色偏暗。
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围观,学习下.
又要压缩,又要不失真,好像挺难的.
C#有时候就是这个样子,很多细节点很难控制,毕竟好多东西都是微软封装好的,
你可以不用微软实现好的东西.自己去实现更符合需求的东西.c#在实现上没障碍.
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压缩之后自然就会变暗，因为像素少了，那就提亮。。。。
希望图片缩小后还是24位真彩色，不能提亮，因为并不是所有的图片都会暗，全部提亮有些图片就会泛白。
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有的时候我也觉得很蛋疼,
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Image本身就有获取thumbnail的方法。
不能用么？
还有就是new一个Image的时候可以用另一个做原始图片。
这些内置方法应该都可以搞定啊。