Image resize on the fly

[fran7]

Hi, I have this asp.net code to resize my images. It works fine although it resizes images without keeping the aspect ratio. My image display page is an .asp page extension.

I would rather keep aspect ratio of my images. Could anyone tell me if there is a tinker one could do with this code to do that or would i need to look for another code to do the job.

Thanks in advance

Richard

<%@ OutputCache Duration="600" VaryByParam="*" %>
<%@ Page Debug="false" %>
<%@ Import Namespace="System.Drawing" %>
<%@ Import Namespace="System.Drawing.Imaging" %>
<%@ Import Namespace="System.IO" %>
<script language="VB" runat="server">
 
    Sub Page_Load(ByVal sender As Object, ByVal e As EventArgs)
 
        On Error Resume Next        
 
        'retrieve relative path to image
        Dim imageUrl As String = HttpUtility.UrlDecode(Request.QueryString("img"))    
        dim doresize As Boolean
        doresize=true       
 
        response.contenttype="image/jpeg"
 
        Dim pictureResizeSecCode As String = "quickresize" 'change this code!
        Dim resizePictureToPx As String = HttpUtility.UrlDecode(Request.QueryString("resizePictureToPx"))
 
        'prepare thumbnail
        Dim fullSizeImg As System.Drawing.Image
        fullSizeImg = System.Drawing.Image.FromFile(Server.MapPath(imageUrl))        
 
        If Request.QueryString("getWidthOnly") = "true" Then
            Response.Write(fullSizeImg.Width)
            fullSizeImg.Dispose()
            Response.End()
        End If
 
        If fullSizeImg Is Nothing Then Response.End()            
 
        '??
        Dim dummyCallBack As System.Drawing.Image.GetThumbnailImageAbort
        dummyCallBack = New System.Drawing.Image.GetThumbnailImageAbort(AddressOf ThumbnailCallback)
 
        Dim thumbNailImg As System.Drawing.Image
        Dim newWidth As Integer
        Dim newHeight As Integer
        Dim maxSize As Integer
        If IsNumeric(Request.QueryString("maxSize")) And Request.QueryString("maxSize") <> "" Then
            maxSize = Request.QueryString("maxSize")
        Else
            maxSize = 0
        End If    
 
        'calculate new widht/height, if any  
 
        If fullSizeImg.Width > maxSize Or fullSizeImg.Height > maxSize Then            
 
            'for better quality
            fullSizeImg.RotateFlip(System.Drawing.RotateFlipType.Rotate90FlipX)
            fullSizeImg.RotateFlip(System.Drawing.RotateFlipType.Rotate90FlipX)
 
            If fullSizeImg.Width >= fullSizeImg.Height Then
                newWidth = maxSize
                newHeight = (fullSizeImg.Height / fullSizeImg.Width) * maxSize
            Else
                newWidth = (fullSizeImg.Width / fullSizeImg.Height) * maxSize
                newHeight = maxSize
            End If
        Else
 
            newWidth = fullSizeImg.Width
            newHeight = fullSizeImg.Height
            doresize = False
 
        End If
 
        dim FSR as string = Request.QueryString("FSR")
        IF FSR IS NOTHING ANDALSO FSR.length = 0 Then
        FSR="0"
        END IF
 
        If FSR = "1" Then
            If newWidth < newHeight Then
                thumbNailImg = fullSizeImg.GetThumbnailImage(newWidth * (newHeight / newWidth), newHeight * (newHeight / newWidth), dummyCallBack, IntPtr.Zero)
                thumbNailImg = CropImage(thumbNailImg, New Point(0, (newHeight - newWidth) / 2), New Point(newHeight, newHeight + (newHeight - newWidth) / 2))
            Else
                thumbNailImg = fullSizeImg.GetThumbnailImage(newWidth * (newWidth / newHeight), newHeight * (newWidth / newHeight), dummyCallBack, IntPtr.Zero)
                thumbNailImg = CropImage(thumbNailImg, New Point((newWidth - newHeight) / 2, 0), New Point(newWidth + ((newWidth - newHeight) / 2), newWidth))
        End If                
        Else
            If doresize=True Then
                thumbNailImg = fullSizeImg.GetThumbnailImage(newWidth, newHeight, dummyCallBack, IntPtr.Zero)
            else                
                thumbNailImg = fullSizeImg                    
            End If
        End If
 
 
        createOutput(thumbNailImg)                   
 
 
        'Clean up / Dispose...
        thumbNailImg.Dispose()
 
        'Clean up / Dispose...
        fullSizeImg.Dispose()
 
        On Error GoTo 0
    End Sub
 
    Sub createOutput(ByRef ImageObj As System.Drawing.Image)
 
        On Error Resume Next
 
        Dim specialEffect as String = HttpUtility.UrlDecode(Request.QueryString("SE"))
 
        select case specialEffect
            case "1"
                PureBW (ImageObj)
            case "2"
                GrayScale (ImageObj)
            case "3"
                PixelLoopConvert (ImageObj)
 
        end select
 
        ImageObj.Save(Response.OutputStream, ImageFormat.Jpeg)
 
        On Error GoTo 0
 
    End Sub
 
    Private Function CropImage(ByVal OriginalImage As Bitmap, ByVal TopLeft As Point, ByVal BottomRight As Point) As Bitmap
        Dim btmCropped As New Bitmap((BottomRight.Y - TopLeft.Y), (BottomRight.X - TopLeft.X))
        Dim grpOriginal As Graphics = Graphics.FromImage(btmCropped)
 
        grpOriginal.DrawImage(OriginalImage, New Rectangle(0, 0, btmCropped.Width, btmCropped.Height), _
            TopLeft.X, TopLeft.Y, btmCropped.Width, btmCropped.Height, GraphicsUnit.Pixel)
        grpOriginal.Dispose()
 
        Return btmCropped
    End Function
 
 
    Function ThumbnailCallback() As Boolean
 
        Return False
 
    End Function
 
    Public Function PureBW(ByVal image As System.Drawing.Bitmap, Optional ByVal Mode As BWMode = BWMode.By_Lightness, Optional ByVal tolerance As Single = 0) As System.Drawing.Bitmap
        Dim x As Integer
        Dim y As Integer
        If tolerance > 1 Or tolerance < -1 Then
            Throw New ArgumentOutOfRangeException
            Exit Function
        End If
        For x = 0 To image.Width - 1 Step 1
            For y = 0 To image.Height - 1 Step 1
                Dim clr As Color = image.GetPixel(x, y)
                If Mode = BWMode.By_RGB_Value Then
                    If (CInt(clr.R) + CInt(clr.G) + CInt(clr.B)) > 383 - (tolerance * 383) Then
                        image.SetPixel(x, y, Color.White)
                    Else
                        image.SetPixel(x, y, Color.Black)
                    End If
                Else
                    If clr.GetBrightness > 0.5 - (tolerance / 2) Then
                        image.SetPixel(x, y, Color.White)
                    Else
                        image.SetPixel(x, y, Color.Black)
                    End If
                End If
            Next
        Next
        Return image
    End Function
 
    Enum BWMode
        By_Lightness
        By_RGB_Value
    End Enum
 
    Public Function GrayScale (ByVal image As System.Drawing.Bitmap)
 
        Dim X As Integer
        Dim Y As Integer
        Dim clr As Integer
 
        For X = 0 To image.Width - 1
            For Y = 0 To image.Height - 1
                clr = (CInt(image.GetPixel(X, Y).R) + _
                       image.GetPixel(X, Y).G + _
                       image.GetPixel(X, Y).B) \ 3
                image.SetPixel(X, Y, Color.FromArgb(clr, clr, clr))
            Next Y
        Next X
 
        return image
 
    End Function
 
    Public Function PixelLoopConvert (ByVal Image As System.Drawing.Bitmap)    
 
    For i As Integer = 0 To Image.Width - 1
      For j As Integer = 0 To Image.Height - 1
        Dim iRed As Integer = Image.GetPixel(i, j).R
        Dim iGreen As Integer = Image.GetPixel(i, j).G
        Dim iBlue As Integer = Image.GetPixel(i, j).B
 
        ' Bereken de nieuwe RGB-waarde voor deze pixel:
        Dim iSepiaRed As Integer = Math.Min(Convert.ToInt32(iRed * 0.393 + iGreen * 0.769 + iBlue * 0.189), 255)
        Dim iSepiaGreen As Integer = Math.Min(Convert.ToInt32(iRed * 0.349 + iGreen * 0.686 + iBlue * 0.168), 255)
        Dim iSepiaBlue As Integer = Math.Min(Convert.ToInt32(iRed * 0.272 + iGreen * 0.534 + iBlue * 0.131), 255)
 
        ' Wijzig de RGB-waarde van de huidige pixel van de oude naar de nieuwe:
        Image.SetPixel(i, j, Color.FromArgb(iSepiaRed, iSepiaGreen, iSepiaBlue))
      Next
    Next
 
    Return Image
 
  End Function
 
</script>
 
 

<img src="showthumb.aspx?fsr=1&amp;maxsize=200&amp;img=<%=Server.URLPathEncode(CStr(thumbnail))%>"/>

[Frinavale]

The way I keep the aspect ratio of my thumbnail images is to reduce the original height and width at the same rate until they both fit within the boundaries of my size restrictions.

Something like:

Dim newHeight As Integer = fullSizeImg.Height
Dim newWidth As Integer = fullSizeImg.Width
If  newHeight > maxSize Or  newWidth > maxSize Then
  While newHeight > maxSize Or newWidth > smallWidth
    newHeight = newHeight - (newHeight * 0.05)
    newWidth = newWidth - (newWidth * 0.05)
  End While
End If

-Frinny