话不多说，请看代码：

/// <summary> /// 根据指定尺寸得到按比例缩放的尺寸,返回true表示以更改尺寸 /// </summary> /// <param name="picWidth">图片宽度</param> /// <param name="picHeight">图片高度</param> /// <param name="specifiedWidth">指定宽度</param> /// /// <param name="specifiedHeight">指定高度</param> /// <returns>返回true表示以更改尺寸</returns> private bool GetPicZoomSize(ref int picWidth, ref int picHeight, int specifiedWidth, int specifiedHeight) { int sW = 0, sH = 0; Boolean isZoomSize = false; //按比例缩放 Size tem_size = new Size(picWidth, picHeight); if (tem_size.Width > specifiedWidth || tem_size.Height > specifiedHeight) //将**改成c#中的或者操作符号 { if ((tem_size.Width * specifiedHeight) > (tem_size.Height * specifiedWidth)) { sW = specifiedWidth; sH = (specifiedWidth * tem_size.Height) / tem_size.Width; } else { sH = specifiedHeight; sW = (tem_size.Width * specifiedHeight) / tem_size.Height; } isZoomSize = true; } else { sW = tem_size.Width; sH = tem_size.Height; } picHeight = sH; picWidth = sW; return isZoomSize; } /// <summary> /// 无损压缩图片 /// </summary> /// <param name="sFile">原图片</param> /// <param name="dFile">压缩后保存位置</param> /// <param name="dHeight">高度</param> /// <param name="dWidth">宽度</param> /// <param name="flag">压缩质量 1-100</param> /// <returns></returns> public bool GetPicThumbnail(string sFile, string dFile, int dHeight, int dWidth, int flag) { System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile); ImageFormat tFormat = iSource.RawFormat; int sW = iSource.Width, sH = iSource.Height; GetPicZoomSize(ref sW, ref sH, dWidth, dHeight); Bitmap ob = new Bitmap(dWidth, dHeight); Graphics g = Graphics.FromImage(ob); g.Clear(Color.WhiteSmoke); g.CompositingQuality = CompositingQuality.HighQuality; g.SmoothingMode = SmoothingMode.HighQuality; g.InterpolationMode = InterpolationMode.HighQualityBicubic; g.DrawImage(iSource, new Rectangle((dWidth - sW) / 2, (dHeight - sH) / 2, sW, sH), 0, 0, iSource.Width, iSource.Height, GraphicsUnit.Pixel); g.Dispose(); //以下代码为保存图片时，设置压缩质量 EncoderParameters ep = new EncoderParameters(); long[] qy = new long[1]; qy[0] = flag;//设置压缩的比例1-100 EncoderParameter eParam = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, qy); ep.Param[0] = eParam; try { ImageCodecInfo[] arrayICI = ImageCodecInfo.GetImageEncoders(); ImageCodecInfo jpegICIinfo = null; for (int x = 0; x < arrayICI.Length; x++) { if (arrayICI[x].FormatDescription.Equals("JPEG")) { jpegICIinfo = arrayICI[x]; break; } } if (jpegICIinfo != null) { ob.Save(dFile, jpegICIinfo, ep);//dFile是压缩后的新路径 } else { ob.Save(dFile, tFormat); } return true; } catch { return false; } finally { iSource.Dispose(); ob.Dispose(); } }

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