自己筆記 - ASP.net 圖片動態縮圖 (增加截圖功能進階版...) @ 小雕雕的家

之前寫了一些ASP.net動態縮圖的東西....

自己筆記 - ASP.net 圖片動態縮圖

自己筆記 - ASP.net 圖片動態縮圖 (高畫質續篇)

但發現還不是很完美...

ex:

1.不能等比例縮圖,一定要決定寬高

2.不能截圖片的寬與高

3.只能針對固定路徑的圖片縮圖

所以想說來改一下....

然後完成後的 code 如下.....

(我是寫成泛型處理常式)

<%@ WebHandler Language="VB" Debug="true" %>

Imports System
Imports System.Web
Imports System.IO
Imports System.Drawing
Imports System.Drawing.Imaging
Public Class RsizeImg : Implements IHttpHandler

   Public Sub ProcessRequest(ByVal context As HttpContext) Implements IHttpHandler.ProcessRequest
   context.Response.ContentType = "image/jpeg"
   context.Response.BufferOutput = True
   Dim files As String = context.Request("file") '檔名
   Dim Folder As String = "" '要存放縮圖的資料夾
   Dim filename As String = ""
   Dim Saveas As String = ""
   Dim w As Integer = 0 '要縮圖的寬
   Dim h As Integer = 0 '要縮圖的高
   Dim cuth As Integer = 0 '要截圖的高
   Dim cutw As Integer = 0 '要截圖的寬

   If context.Request("w") IsNot Nothing Then
   w = context.Request("w")
   End If
   If context.Request("h") IsNot Nothing Then
   h = context.Request("h")
   End If
   If context.Request("f") IsNot Nothing Then
   Folder = context.Request("f") & "\"
   End If
   If context.Request("cuth") IsNot Nothing Then
   cuth = context.Request("cuth")
   End If
   If context.Request("cutw") IsNot Nothing Then
   cutw = context.Request("cutw")
   End If

   '縮圖輸出位置
   Dim End_path As String = "Z:\ImagesUpload\" & Folder & "\resize\"

   If InStr(files, "/") > 0 Then
   filename = Right(files, InStrRev(files, "/") - 1)
   Else
   filename = files
   End If

   '不同格式的圖產生不同的檔名
   If cuth > 0 Then
   Saveas = End_path & filename & "_" & w & "_" & h & "_ch" & cuth & ".jpg"
   ElseIf cutw > 0 Then
   Saveas = End_path & filename & "_" & w & "_" & h & "_cw" & cutw & ".jpg"
   Else
   Saveas = End_path & filename & "_" & w & "_" & h & ".jpg"
   End If

   Dim fileExists As Boolean

   '判斷有無縮圖,有則直接用縮圖不用再產生了
   fileExists = My.Computer.FileSystem.FileExists(Saveas)
   If fileExists = False Then
   '原圖位置,根據傳入的folder名稱切換資料夾
   Dim SFileStream As FileStream = File.OpenRead("Z:\ImagesUpload\" & Folder & filename)
   Dim TFileStream As FileStream = File.Create(Saveas)
   ResizeImage(0.1, SFileStream, TFileStream, w, h, cutw, cuth)
   SFileStream.Close()
   TFileStream.Close()
   context.Response.ContentType = "image/jpeg"
   context.Response.WriteFile(Saveas)
   Else
   context.Response.ContentType = "image/jpeg"
   context.Response.WriteFile(Saveas)
   End If
   End Sub

   Public ReadOnly Property IsReusable() As Boolean Implements IHttpHandler.IsReusable
   Get
   Return False
   End Get
   End Property

   Function ThumbNailCallBack() As Boolean
   Return False
   End Function

   Public Sub ResizeImage(ByVal scaleFactor As Double, ByVal fromStream As Stream, ByVal toStream As Stream, ByVal w As Integer, ByVal h As Integer, ByVal cutw As Integer, ByVal cuth As Integer)
   Dim image As System.Drawing.Image = System.Drawing.Image.FromStream(fromStream)
   If h = 0 Then
   h = image.Height
   End If
   If w = 0 Then
   w = image.Width
   End If
   '這函數網路上ㄎㄧㄤ來的...計算圖片等比寬高並回傳integer陣列
   Dim thumbnailScale As Integer() = getThumbnailImageScale(w, h, image.Width, image.Height)
   Dim cw As Integer = w
   Dim ch As Integer = h

   If cutw > 0 Then
   cw = cutw
   End If
   If cuth > 0 Then
   ch = cuth
   End If
   '如果要截的寬度超過等比縮圖的寬度~就以等比縮的寬為主
   If thumbnailScale(0) < cw Then
   cw = thumbnailScale(0)
   End If
   '同上
   If thumbnailScale(1) < ch Then
   ch = thumbnailScale(1)
   End If
   '產生圖片囉,順便截圖
   Dim thumbnailBitmap As Bitmap = New Bitmap(cw, ch)
   Dim thumbnailGraph As Graphics = Graphics.FromImage(thumbnailBitmap)
   '這些屬性是要高品質的意思
   thumbnailGraph.CompositingQuality = Drawing2D.CompositingQuality.HighQuality
   thumbnailGraph.SmoothingMode = Drawing2D.SmoothingMode.HighQuality
   thumbnailGraph.InterpolationMode = Drawing2D.InterpolationMode.High
   '產生矩形的畫布並將產生的圖形放到畫布中
   'MSDN http://msdn.microsoft.com/en-us/library/yws82c40.aspx
   Dim imageRectangle As Rectangle = New Rectangle(0, 0, thumbnailScale(0), thumbnailScale(1))
   thumbnailGraph.DrawImage(image, imageRectangle)
   '存檔 + 物件消滅
   thumbnailBitmap.Save(toStream, image.RawFormat)
   thumbnailGraph.Dispose()
   thumbnailBitmap.Dispose()
   image.Dispose()
   End Sub

   Function getThumbnailImageScale(ByVal maxWidth As Integer, ByVal maxHeight As Integer, ByVal oldWidth As Integer, ByVal oldHeight As Integer) As Integer()
   Dim result() As Integer = New Integer() {0, 0}
   Dim widthDividend As Single, heightDividend As Single, commonDividend As Single
   widthDividend = oldWidth / maxWidth
   heightDividend = oldHeight / maxHeight
   If (heightDividend > widthDividend) Then
   commonDividend = heightDividend
   Else
   commonDividend = widthDividend
   End If
   result(0) = CType((oldWidth / commonDividend), Integer)
   result(1) = CType((oldHeight / commonDividend), Integer)
   Return result
   End Function
End Class