' Macro by Gerry Daumiller Montana State Library 5/1/2003
' Makes the white color of the DRG TIFF images in an
' ArcMap data frame transparent.

'NOTE FOR ARCMAP 9 USERS:
' This script was written for ArcMap 8.3 and does not work for 9.0.
' The Arc 9 version of this script is at
' http://mslapps.mt.gov/Geographic_Information/Data/Topographic/drgtransparent9.txt

' To run this macro, open the Tools-Macros-Macros dialog, type a module
' and macro name into the "Macro Name" box (such as drg.Drgtrans), paste
' the text from this file into the Visual Basic editor between the
' "Sub Drgtrans()" and "End Sub" lines, close the Visual Basic editor,
' and use the Tools-Macros dialog to run the "drgtrans" macro.
' ArcMap will spend some time with each image saying
' "Building Tables", and will eventually come back and re-draw the images.

Dim pMxDoc As IMxDocument
Dim pLy As ILayer
Dim pRasLy As IRasterLayer
Dim pRasRend As IRasterUniqueValueRenderer
Dim pSym As IColorSymbol
Dim pColor As IRgbColor
Dim iNum As Integer

'Make a transparent color and symbol.
Set pColor = New RgbColor
Set pSym = New ColorSymbol
pColor.NullColor = True
pSym.Color = pColor

'Cycle through the view and find all Tiff images
Set pMxDoc = ThisDocument
For iNum = 0 To pMxDoc.FocusMap.LayerCount - 1
  Set pLy = pMxDoc.FocusMap.Layer(iNum)
  If TypeOf pLy Is RasterLayer And InStr(pLy.Name, ".tif") <> 0 Then
    Set pRasLy = pLy
    Set pRasRend = pRasLy.Renderer
    pRasRend.Symbol(0, 1) = pSym
  End If
Next iNum
Set pColor = Nothing
Set pSym = Nothing

pMxDoc.ActiveView.Refresh