Net core中使用System.Drawing对上传的图片流进行压缩(示例代码)_实用技巧_

/// 
 /// 图片压缩 /// 
 /// 原图片位置 /// 压缩后图片位置 /// 图片压缩后的高度 /// 图片压缩后的宽度 /// 图片压缩比0-100,数值越小压缩比越高，失真越多 ///  public static bool GetPicThumbnailTest(string sFile, string dFile, int dHeight, int dWidth, int flag) { System.Drawing.Image iSource = System.Drawing.Image.FromFile(sFile); //如果为参数为0就保持原图片的高宽嘛（不然想保持原图外面还要去读取一次） if (dHeight == 0) { dHeight = iSource.Height; } if (dWidth == 0) { dWidth = iSource.Width; } ImageFormat tFormat = iSource.RawFormat; int sW = 0, sH = 0; //按比例缩放 Size tem_size = new Size(iSource.Width, iSource.Height); if (tem_size.Width > dHeight || tem_size.Width > dWidth) { if ((tem_size.Width * dHeight) > (tem_size.Width * dWidth)) { sW = dWidth; sH = (dWidth * tem_size.Height) / tem_size.Width; } else { sH = dHeight; sW = (tem_size.Width * dHeight) / tem_size.Height; } } else { sW = tem_size.Width; sH = tem_size.Height; } 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(); } }

foreach (IFormFile file in files)//获取多个文件列表集合 { if (file.Length > 0) { //获取图片上传的流 Stream stream = file.OpenReadStream(); //直接从流里边变成图片 System.Drawing.Image iSource = System.Drawing.Image.FromStream(stream); } }

/// 
 /// 上传图片文件 /// 
 ///  [HttpPost] public async Task UploadImageFile_WeChat() { var file = IHttpContextAccessor.HttpContext.Request.Form.Files; if (file == null || file.Count == 0) { return Fail("未上传有效文件"); } var result = new List(); foreach (var item in file) { var ExtensionName = Path.GetExtension(item.FileName).ToLower(); var RemotePath = getRemotePath(ExtensionName); if (string.IsNullOrEmpty(RemotePath) || !"image".Equals(RemotePath)) { return Fail("不支持此类型文件的上传"); } string remotePath = PathFormatter.Format(item.FileName + "." + ExtensionName, "/upload/" + RemotePath + "/image" + "/{yyyy}{mm}/{dd}{time}{rand:6}"); string savePath = AppDomain.CurrentDomain.BaseDirectory + "/wwwroot/" + remotePath; MemoryStream memoryStream = new MemoryStream(); //ob.Save(memoryStream, jpegICIinfo, ep);//这里的ob就是压缩后的Bitmap对象 var k = GetPicThumbnail(item.OpenReadStream(), 0, 0, 70, memoryStream); System.Drawing.Image imgSource = System.Drawing.Image.FromStream(memoryStream); imgSource.Save(savePath); if (k) { result.Add(new { url = Config.FileConfig.fileUrl + remotePath, remoteUrl = remotePath, name = item.FileName }); } } return Success("上传成功", result); } private bool GetPicThumbnail(Stream stream, int dHeight, int dWidth, int flag, Stream outstream) { //可以直接从流里边得到图片,这样就可以不先存储一份了 System.Drawing.Image iSource = System.Drawing.Image.FromStream(stream); //如果为参数为0就保持原图片 if (dHeight == 0) { dHeight = iSource.Height; } if (dWidth == 0) { dWidth = iSource.Width; } ImageFormat tFormat = iSource.RawFormat; int sW = 0, sH = 0; //按比例缩放 Size tem_size = new Size(iSource.Width, iSource.Height); if (tem_size.Width > dHeight || tem_size.Width > dWidth) { if ((tem_size.Width * dHeight) > (tem_size.Width * dWidth)) { sW = dWidth; sH = (dWidth * tem_size.Height) / tem_size.Width; } else { sH = dHeight; sW = (tem_size.Width * dHeight) / tem_size.Height; } } else { sW = tem_size.Width; sH = tem_size.Height; } 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) { //可以存储在流里边; ob.Save(outstream, jpegICIinfo, ep); } else { ob.Save(outstream, tFormat); } return true; } catch { return false; } finally { iSource.Dispose(); ob.Dispose(); } }

MemoryStream memoryStream = new MemoryStream(); ob.Save(memoryStream, jpegICIinfo, ep);//这里的ob就是压缩后的Bitmap对象

System.Drawing.Image imgSource = System.Drawing.Image.FromStream(memoryStream); imgSource.Save("url");

//实例化一个内存流，存放压缩后的图片 MemoryStream ysstream = new MemoryStream(); bool issuc = ImageTool.GetPicThumbnail(stream, 300, 300, 80, ysstream); if (issuc) { //通过流上传图片到七牛云 //HttpResult result = um.UploadStream(stream, saveKey, uploadToken); //从内存流里边读出来字节数组上传到七牛云 HttpResult result = um.UploadData(ysstream.ToArray(), saveKey, uploadToken); if (result.Code == 200) { return Json(result.Text); } else { throw new Exception(result.RefText);//上传失败错误信息 } } else { throw new Exception("图片压缩失败");//上传失败错误信息 }