asp.net上传图片自动生成缩略图功能代码
if (FileUpload1.FileName.ToString() == "") { Label3.Text = "请选择图片!"; } else { Boolean FileOK = false; if (this.FileUpload1.HasFile) { // 限制上传图片小于 2M if (FileUpload1.PostedFile.ContentLength <= 2097152) { // 图片 Guid 重命名 Session["WorkingImage"] = Guid.NewGuid().ToString() + Path.GetExtension(FileUpload1.FileName.ToString()).ToLower(); String FileExtension = Path.GetExtension(Session["WorkingImage"].ToString()).ToLower(); String[] allowedExtensions = { ".png", ".jpeg", ".jpg", ".gif" }; for (int i = 0; i < allowedExtensions.Length; i++) { if (FileExtension == allowedExtensions[i]) { FileOK = true; } } } // 上传图片大于 2M 警告 else { FileOK = false; Response.Write("<script language=javascript>alert('图片不要超过 2M 大小!');window.location.href=window.location.href;</script>"); } } if (FileOK) { try { //生成原图 Byte[] oFileByte = new byte[this.FileUpload1.PostedFile.ContentLength]; System.IO.Stream oStream = this.FileUpload1.PostedFile.InputStream; System.Drawing.Image oImage = System.Drawing.Image.FromStream(oStream); int oWidth = oImage.Width; //原图宽度 int oHeight = oImage.Height; //原图高度 int tWidth; //缩略图宽度 int tHeight; //缩略图高度 //按比例计算出缩略图的宽度和高度 if (oWidth >= oHeight) { tWidth = 300; tHeight = (int)Math.Floor(Convert.ToDouble(oHeight) * (Convert.ToDouble(tWidth) / Convert.ToDouble(oWidth))); } else { tHeight = 300; tWidth = (int)Math.Floor(Convert.ToDouble(oWidth) * (Convert.ToDouble(tHeight) / Convert.ToDouble(oHeight))); } //生成缩略原图 Bitmap tImage = new Bitmap(tWidth, tHeight); Graphics g = Graphics.FromImage(tImage); //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(Color.Transparent); g.DrawImage(oImage, new Rectangle(0, 0, tWidth, tHeight), new Rectangle(0, 0, oWidth, oHeight), GraphicsUnit.Pixel); string fullFileName = this.FileUpload1.PostedFile.FileName.ToString(); fullFileName = fullFileName.Remove(fullFileName.LastIndexOf('.')); string filename = fullFileName.Substring(fullFileName.LastIndexOf("\\") + 1); //存储路径 string strLocation = path.ToString(); string tFullName = strLocation + Session["WorkingImage"].ToString(); try { // 上传缩略 tImage.Save(tFullName, System.Drawing.Imaging.ImageFormat.Jpeg); //输出上传成功提示并显示保存路径 TextBox3.Text = "uploadfiles/product/" + Session["WorkingImage"].ToString(); // pic_upload.Visible = false; // pic_crop.Visible = true; // 读取缩略图 path = "../uploadfiles/product/" + Session["WorkingImage"].ToString(); } catch (Exception) { Response.Write("<script language=javascript>alert('上传失败,请重试!');window.location.href=window.location.href;</script>"); } finally { //释放资源 oImage.Dispose(); g.Dispose(); tImage.Dispose(); } } catch (Exception) { Response.Write("<script language=javascript>alert('上传失败,请重试!');window.location.href=window.location.href;</script>"); } } }