Hi again Peter,
I have attempted to use this hashing code in the following scenario:
Get an image, base64 encode and write to xml file.
Reverse this process to get image file back.
Compare hashes of before and after - they do not match... image looks
identical visually, and has same filesize and other properties... can you
suggest a way I can store these images to an XML file and get the exact same
file back when I extract the image again...?
The XML code is something like this:
Private Sub WriteXMLImage(ByVal strSourceFilePathAndName As String,
Optional ByVal strTargetFilePathAndName As String = "")
If strSourceFilePathAndName <> "" Then
Dim strSourceExtension As String = ""
strSourceExtension = strSourceFilePathAndName.Substring
(strSourceFilePathAndName.Length - 3)
'Destination filename not supplied so make one up
If strTargetFilePathAndName = "" Then
strTargetFilePathAndName =
strSourceFilePathAndName.Substring(0, strSourceFilePathAndName.Length
- 3)
& "xml"
End If
Dim xmlTextWriter As New XmlTextWriter
(strTargetFilePathAndName, Encoding.UTF8)
xmlTextWriter.Formatting = Formatting.Indented
xmlTextWriter.WriteStartDocument()
' Copy the picture into a MemoryStream.
Dim memory_stream As New MemoryStream
Dim objImageOriginal As Image
objImageOriginal = New Bitmap(strSourceFilePathAndName)
'objImageOriginal = objImageOriginal.FromFile
(strSourceFilePathAndName)
objImageOriginal.Save(memory_stream, GetFormat
(strSourceExtension))
' Copy the MemoryStream data into a Byte array.
Dim objBytes(memory_stream.Length - 1) As Byte
objBytes = memory_stream.ToArray()
' Make a Picture element.
xmlTextWriter.WriteStartElement("Picture")
xmlTextWriter.WriteAttributeString("Encoding",
Nothing,
"Base64")
' Save Image details and encoding as Attributes
xmlTextWriter.WriteAttributeString("Bytes",
objBytes.Length)
xmlTextWriter.WriteAttributeString("Height",
objImageOriginal.Height)
xmlTextWriter.WriteAttributeString("Width",
objImageOriginal.Width)
xmlTextWriter.WriteAttributeString("Type",
strSourceExtension)
xmlTextWriter.WriteBase64(objBytes, 0, objBytes.Length)
xmlTextWriter.WriteEndElement()
xmlTextWriter.WriteEndDocument()
xmlTextWriter.Close()
objImageOriginal.Dispose()
MsgBox("XML file created successfully ! ",
MsgBoxStyle.Information, "Success !")
Else
MsgBox("A target file name must be supplied.",
MsgBoxStyle.OKOnly + MsgBoxStyle.Exclamation, "Error")
Exit Sub
End If
End Sub
Private Sub ReadXMLImage(ByVal strSourceFilePathAndName As String)
If strSourceFilePathAndName <> "" Then
Dim objImageOriginal As Image
Dim blnValidXML As Boolean = False
Dim strImageExtension As String = ""
Dim strTargetFilePathAndName As String = ""
' Load the picture from XML
Dim xmlTextReader As New XmlTextReader
(strSourceFilePathAndName)
' Skip until we find the Picture node.
Do While xmlTextReader.Read()
' See if this is the Picture node.
If xmlTextReader.Name = "Picture" Then
blnValidXML = True
' Allocate room for the byte data and get all
attribute
values.
Dim intNumBytes As Integer =
xmlTextReader.GetAttribute
("Bytes")
Dim h As Integer =
xmlTextReader.GetAttribute("Height")
Dim w As Integer =
xmlTextReader.GetAttribute("Width")
strImageExtension =
xmlTextReader.GetAttribute("Type")
'Refresh the target file according to parameters
read
from XML file Type Attribute
strTargetFilePathAndName = Replace
(strSourceFilePathAndName, ".xml", "New." &
strImageExtension)
'lbl_Message.Text = "Source File : " &
strSourceFilePathAndName & vbCrLf & "Target File : " &
strTargetFilePathAndName
Dim bytes(intNumBytes - 1) As Byte
' Translate the encoded data back into byte data.
Select Case xmlTextReader.GetAttribute
("Encoding").ToLower
Case "base64"
xmlTextReader.ReadBase64(bytes, 0,
intNumBytes)
Case "binhex"
xmlTextReader.ReadBinHex(bytes, 0,
intNumBytes)
Case Else
MsgBox("Unknown image encoding
'" &
xmlTextReader.GetAttribute("Encoding") & "'", _
MsgBoxStyle.Exclamation, "Unknown
Encoding")
Exit Sub
End Select
' Allocate a MemoryStream and a BinaryWriter
attached
to it.
Dim memory_stream As New MemoryStream
Dim binary_writer As BinaryWriter = New
BinaryWriter
(memory_stream)
' Copy the bytes into the BinaryWriter and
MemoryStream.
binary_writer.Write(bytes, 0, intNumBytes)
binary_writer.Flush()
' Load the picture from the memory stream and
save it
and show in the Picture box.
memory_stream.Position = 0
objImageOriginal = Image.FromStream(memory_stream)
'objImageOriginal.Save(strTargetFilePathAndName,
GetFormat(strImageExtension))
objImageOriginal.Save(strTargetFilePathAndName)
'Me.PB_sample.Image =
Image.FromStream(memory_stream)
'PB_sample.SizeMode =
PictureBoxSizeMode.CenterImage
binary_writer.Close()
Exit Do
End If
Loop
xmlTextReader.Close()
If blnValidXML Then
MsgBox(strImageExtension.ToUpper & " file created
successfully ! ", MsgBoxStyle.Information, "Success !")
Else
MsgBox("Invalid XML file format ! ",
MsgBoxStyle.Critical,
"Error !")
End If
Else
MsgBox("An xml file containing the image must be
selected.",
MsgBoxStyle.OKOnly + MsgBoxStyle.Information, "File error")
Exit Sub
End If
End Sub
Private Function GetFormat(ByVal ImageType As String) As
System.Drawing.Imaging.ImageFormat
Select Case ImageType.ToUpper
Case "JPG"
Return ImageFormat.Jpeg
Case "GIF"
Return ImageFormat.Gif
Case "PNG"
Return ImageFormat.Png
Case "BMP"
Return ImageFormat.Bmp
End Select
End Function
Also, I want (need) to do this for image formats that aren't recognised by
the image object (Wavelet Scalar Quantization .wsq format)... any idea how I
can achieve this?
Cheers again for you help...
"Peter Huang" <v-******@online.microsoft.com> wrote in message
news:7y**************@cpmsftngxa06.phx.gbl...
Hi Bob,
If you have any question on this issue please post here.
Regards,
Peter Huang
Microsoft Online Partner Support
Get Secure! www.microsoft.com/security
This posting is provided "as is" with no warranties and confers no rights.
