Convert hex string (image) to base64 (for browser rendering) in VBScript

Question

I have a script that outputs a .bmp captcha image.

The image is built in hexadecimal, and converted to binary and sent to the browser via response.binaryWrite

Answer 1

The Microsoft.XMLDOM has built in converters for bin.base64 and bin.hex. I wrote functions that demonstrate how to use this:

Function TextToBinary(text, dataType)
  Dim dom
  Set dom = CreateObject("Microsoft.XMLDOM")
  dom.loadXML("")
  dom.documentElement.nodeTypedValue = text
  dom.documentElement.dataType = dataType
  TextToBinary = dom.documentElement.nodeTypedValue
End Function

Function BinaryToText(binary, dataType)
  Dim dom
  Set dom = CreateObject("Microsoft.XMLDOM")
  dom.loadXML("")
  dom.documentElement.dataType = dataType
  dom.documentElement.nodeTypedValue = binary
  dom.documentElement.removeAttribute("dt:dt")
  BinaryToText = dom.documentElement.nodeTypedValue
End Function

Function HexToBase64(strHex)
  HexToBase64 = BinaryToText(TextToBinary(strHex, "bin.hex"), "bin.base64")
End Function

Function Base64ToHex(strBase64)
  Base64ToHex = BinaryToText(TextToBinary(strBase64, "bin.base64"), "bin.hex")
End Function

Here's an example of their usage:

MsgBox HexToBase64("41")
MsgBox Base64ToHex("QQ==")

Also look at the ADODB.Stream as a means of working with binary files. It'll work with these routines.