It’s not only img block that accepts Data URIs, in HTML5 audio and video also accept it as a source, as well as standard file URLs.
URI information has this form:
data:[<MIME-type>][;charset=<encoding>][;base64],<data>Would be interesting to hide -hindering download- some graphical elements as binary text, thus needed to encode/decode. So rearranging code from here got a functional tool for this task.
Option Explicit
Private Const clOneMask As Long = 16515072 '000000 111111 111111 111111
Private Const clTwoMask As Long = 258048 '111111 000000 111111 111111
Private Const clThreeMask As Long = 4032 '111111 111111 000000 111111
Private Const clFourMask As Long = 63 '111111 111111 111111 000000
Private Const clHighMask As Long = 16711680 '11111111 00000000 00000000
Private Const clMidMask As Long = 65280 '00000000 11111111 00000000
Private Const clLowMask As Long = 255 '00000000 00000000 11111111
Private Const cl2Exp18 As Long = 262144 '2 to the 18th power
Private Const cl2Exp12 As Long = 4096 '2 to the 12th
Private Const cl2Exp6 As Long = 64 '2 to the 6th
Private Const cl2Exp8 As Long = 256 '2 to the 8th
Private Const cl2Exp16 As Long = 65536 '2 to the 16th
Public Sub sFileEncode64()
Dim iFileIn As Integer
Dim strFullPathFile As String
Dim sBinary As String
iFileIn = VBA.FreeFile()
strFullPathFile = VBA.Environ$("UserProfile") & "\Documents\###." & "png"
Open strFullPathFile For Binary As #iFileIn
sBinary = String$(LOF(iFileIn), Chr$(0))
Get #iFileIn, , sBinary
Close #iFileIn
Debug.Print Encode64(sBinary)
End Sub
Public Function sTest_DecodeURI()
Dim strURI As String
strURI = _
"data:image/png;base64,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" & _
"SjefNL5GePZmpu4kG7OPr1+tOfPyUu3BecWYKcwQcDFmwFKAUo90fhKDInBCAmvqnyMgqUEagQwCoHBDc1rjv9pIlD8IbVkz6qYViIBQGTJPx4k0XpIgEZoRN1Da0cij4VfR0ta3WvBXH/rjdCufv6R2zPgPH/e4pxSBCpeatqPrjNiso203/5s/zA171Mv8+w1LOAAAAAElFTkSuQmCC"
Call Decode64(strURI)
End Function
Public Function Encode64(ByVal sString As String) As String
Dim bTrans(63) As Byte
Dim lPowers8(255) As Long
Dim lPowers16(255) As Long
Dim bOut() As Byte
Dim bIn() As Byte
Dim lChar As Long
Dim lTrip As Long
Dim iPad As Integer
Dim lLen As Long
Dim lTemp As Long
Dim lPos As Long
Dim lOutSize As Long
For lTemp = 0 To 63 'Fill the translation table.
Select Case lTemp
Case 0 To 25
bTrans(lTemp) = 65 + lTemp 'A - Z
Case 26 To 51
bTrans(lTemp) = 71 + lTemp 'a - z
Case 52 To 61
bTrans(lTemp) = lTemp - 4 '1 - 0
Case 62
bTrans(lTemp) = 43 'Chr(43) = "+"
Case 63
bTrans(lTemp) = 47 'Chr(47) = "/"
End Select
Next lTemp
For lTemp = 0 To 255 'Fill the 2^8 and 2^16 lookup tables.
lPowers8(lTemp) = lTemp * cl2Exp8
lPowers16(lTemp) = lTemp * cl2Exp16
Next lTemp
iPad = Len(sString) Mod 3 'See if the length is divisible by 3
If iPad Then 'If not, figure out the end pad and resize the input.
iPad = 3 - iPad
sString = sString & String(iPad, Chr(0))
End If
bIn = StrConv(sString, vbFromUnicode) 'Load the input string.
lLen = ((UBound(bIn) + 1) \ 3) * 4 'Length of resulting string.
lTemp = lLen \ 72 'Added space for vbCrLfs.
lOutSize = ((lTemp * 2) + lLen) - 1 'Calculate the size of the output buffer.
ReDim bOut(lOutSize) 'Make the output buffer.
lLen = 0 'Reusing this one, so reset it.
For lChar = LBound(bIn) To UBound(bIn) Step 3
lTrip = lPowers16(bIn(lChar)) + lPowers8(bIn(lChar + 1)) + bIn(lChar + 2) 'Combine the 3 bytes
lTemp = lTrip And clOneMask 'Mask for the first 6 bits
bOut(lPos) = bTrans(lTemp \ cl2Exp18) 'Shift it down to the low 6 bits and get the value
lTemp = lTrip And clTwoMask 'Mask for the second set.
bOut(lPos + 1) = bTrans(lTemp \ cl2Exp12) 'Shift it down and translate.
lTemp = lTrip And clThreeMask 'Mask for the third set.
bOut(lPos + 2) = bTrans(lTemp \ cl2Exp6) 'Shift it down and translate.
bOut(lPos + 3) = bTrans(lTrip And clFourMask) 'Mask for the low set.
If lLen = 68 Then 'Ready for a newline
bOut(lPos + 4) = 13 'Chr(13) = vbCr
bOut(lPos + 5) = 10 'Chr(10) = vbLf
lLen = 0 'Reset the counter
lPos = lPos + 6
Else
lLen = lLen + 4
lPos = lPos + 4
End If
Next lChar
If bOut(lOutSize) = 10 Then lOutSize = lOutSize - 2 'Shift the padding chars down if it ends with CrLf.
If iPad = 1 Then 'Add the padding chars if any.
bOut(lOutSize) = 61 'Chr(61) = "="
ElseIf iPad = 2 Then
bOut(lOutSize) = 61
bOut(lOutSize - 1) = 61
End If
Encode64 = StrConv(bOut, vbUnicode) 'Convert back to a string and return it.
End Function
Public Function Decode64(ByVal sString As String) As Boolean
Dim lgPosition As Long
Dim strURI As String
Dim strMIMEtype As String
Dim strData As String
'data:[][;charset=][;base64],
'data:image/png;base64,
'data:audio/ogg;base64,
'data:video/webm;base64,
'data:video/mp4;base64,
lgPosition = 1
lgPosition = VBA.InStr(lgPosition, sString, "/")
strMIMEtype = VBA.Mid$(sString, lgPosition + 1, VBA.InStr(lgPosition, sString, ";") - lgPosition - 1)
sString = VBA.Mid$(sString, VBA.InStr(1, sString, ",") + 1)
Dim bOut() As Byte
Dim bIn() As Byte
Dim bTrans(255) As Byte
Dim lPowers6(63) As Long
Dim lPowers12(63) As Long
Dim lPowers18(63) As Long
Dim lQuad As Long
Dim iPad As Integer
Dim lChar As Long
Dim lPos As Long
Dim lTemp As Long
Dim lgRetVal As Long
sString = Replace(sString, vbCr, vbNullString) 'Get rid of the vbCrLfs. These could be in...
sString = Replace(sString, vbLf, vbNullString) 'either order.
lTemp = Len(sString) Mod 4 'Test for valid input.
If lTemp Then
GoTo ErrControl
'Call Err.Raise(vbObjectError, "MyDecode", "Input string is not valid Base64.")
End If
If InStrRev(sString, "==") Then 'InStrRev is faster when you know it's at the end.
iPad = 2 'Note: These translate to 0, so you can leave them...
ElseIf InStrRev(sString, "=") Then 'in the string and just resize the output.
iPad = 1
End If
For lTemp = 0 To 255 'Fill the translation table.
Select Case lTemp
Case 65 To 90
bTrans(lTemp) = lTemp - 65 'A - Z
Case 97 To 122
bTrans(lTemp) = lTemp - 71 'a - z
Case 48 To 57
bTrans(lTemp) = lTemp + 4 '1 - 0
Case 43
bTrans(lTemp) = 62 'Chr(43) = "+"
Case 47
bTrans(lTemp) = 63 'Chr(47) = "/"
End Select
Next lTemp
For lTemp = 0 To 63 'Fill the 2^6, 2^12, and 2^18 lookup tables.
lPowers6(lTemp) = lTemp * cl2Exp6
lPowers12(lTemp) = lTemp * cl2Exp12
lPowers18(lTemp) = lTemp * cl2Exp18
Next lTemp
bIn = StrConv(sString, vbFromUnicode) 'Load the input byte array.
ReDim bOut((((UBound(bIn) + 1) \ 4) * 3) - 1) 'Prepare the output buffer.
For lChar = 0 To UBound(bIn) Step 4
lQuad = lPowers18(bTrans(bIn(lChar))) + lPowers12(bTrans(bIn(lChar + 1))) + _
lPowers6(bTrans(bIn(lChar + 2))) + bTrans(bIn(lChar + 3)) 'Rebuild the bits.
lTemp = lQuad And clHighMask 'Mask for the first byte
bOut(lPos) = lTemp \ cl2Exp16 'Shift it down
lTemp = lQuad And clMidMask 'Mask for the second byte
bOut(lPos + 1) = lTemp \ cl2Exp8 'Shift it down
bOut(lPos + 2) = lQuad And clLowMask 'Mask for the third byte
lPos = lPos + 3
Next lChar
If iPad Then
ReDim Preserve bOut(LBound(bOut) To UBound(bOut) - iPad) 'Chop off any extra bytes.
End If
Dim iFileOut As Integer
iFileOut = VBA.FreeFile()
Open VBA.Environ$("UserProfile") & "\Documents\###." & strMIMEtype For Binary As #iFileOut
Put #iFileOut, , bOut()
Close #iFileOut
'StrConv(bOut, vbUnicode) 'Convert back to a string.
Decode64 = True
ExitProc:
Exit Function
ErrControl:
lgRetVal = VBA.MsgBox("Input string is not valid Base64.", vbCritical, "W A R N I N G")
GoTo ExitProc
End Function