上傳圖片加入浮水印
有時想在上傳圖片後自動加入浮水印圖案，如網站logo之類的，一方面防止盜圖，一方面節省使用繪圖工具修圖的時間，所以在程式中加入是最快最方便的一種選擇。
首先是先準備好你的Fileupload控制項的畫面跟確保能上傳成功，上傳的部分就不多加說明了，直接看浮水印加入的程式碼吧：
Sub join_img(ByRef str_Original As System.Drawing.Image, ByVal str_aterMark As String, ByVal img_path As String, ByVal de_name As String, Optional ByVal type As Integer = 0)
'設定原有圖檔與浮水印圖檔的位置(此例為執行頁面同目錄下)
'Dim original As String = Server.MapPath(img_path & str_Original)
Dim watermark As String = Server.MapPath(img_path & str_aterMark)
'建立兩個圖檔的Image以供稍後操作
Try
Using imageOriginal As System.Drawing.Image = str_Original, imageWatermark As System.Drawing.Image = System.Drawing.Image.FromFile(watermark)
'自原有圖片建立新的Image
Dim newImage As System.Drawing.Image = New Bitmap(imageOriginal)
'由newImage中取得Graphics物件
Using newGraphic As Graphics = Graphics.FromImage(newImage)
'為了讓浮水印出現在圖片右上角, 故要算出浮水印繪製的座標
Dim drawX As Int32 = (imageOriginal.Width - imageWatermark.Width) / 2
Dim drawY As Int32 = (imageOriginal.Height - imageWatermark.Height) / 2
'繪製浮水印
newGraphic.DrawImageUnscaled(imageWatermark, New Point(drawX, drawY))
'儲存有浮水印的新圖片
newImage.Save(Server.MapPath("~/upload/product/" & de_name), ImageFormat.Jpeg)
End Using
End Using
Catch ex As Exception
Response.Write("<span style='color:red;'>" & ex.Message & "</span>")
End Try
End Sub
加入後在做好的上傳程式中叫用即可 ：
Me.join_img(System.Drawing.Image.FromStream(upimgfile), "logo.png", "~/images/product/", file_name, 0) '加入浮水印
想要有點變化的可以再加個Checkbox判斷是否要加入浮水印 :)
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