Manipulating PictureData Property

[Frink]

Hallo,

This is a bit of a knotty one, but I really would like to get it to work.

I want to write to the PictureData property of an image control on a form, but it seems to be read only.

I have written two routines to read/write a byte of data:

Public Sub WriteByte(pvarBitmap, ByVal plngByteOffset As Long, ByVal pbytValue As Byte)
  pvarBitmap(plngByteOffset) = pbytValue
End Sub
Public Function bytReadByte(pvarBitmap, ByVal plngByteOffset As Long) As Byte
  bytReadByte = pvarBitmap(plngByteOffset)
End Function

I have written a test harness to try it out using an array of bytes and the PictureData property of an image control:

  Dim bytArray(0 To 99) As Byte
  MsgBox bytReadByte(Me!imgImage1.PictureData, 0) & " " & bytReadByte(bytArray, 0)
  WriteByte Me!imgImage1.PictureData, 0, 39
  WriteByte bytArray, 0, 39
  MsgBox bytReadByte(Me!imgImage1.PictureData, 0) & " " & bytReadByte(bytArray, 0)

As you can see, this outputs byte 0 of the PictureData and the byte array.
Then it attempts to set byte 0 of the PictureData and the byte array.
Lastly it re-outputs the same bytes as before which I would expect to have the changed values.

Unfortunately, while the byte array code works, the PictureData one doesn't.

I can copy the PictureData into a byte array, change it and copy the byte array back and the PictureData is updated.

Any ideas why the PictureData is sometimes read-only?

- Frink