' ----------------------------------------------------------------------
' DiskFile   : atvegind.ave : Atmos (Veg Index)
' Programmer : Tom Van Niel 
' Created    : 05-Nov-99
' Revisions  : 
' Function   : Calculates a User Specified Vegetation Index
'
' References : Deering, D. W., J. W. Rouse, R. H. Haas, and J. A. Schell,
'                  1975. Measuring forage production of grazing units from
'                  Landsat MSS data, Proceedings, 10th International
'                  Symposium on Remote Sensing of Environment, Vol. 2, pp.
'                  1169-1178.
'            : Huete, A. R., 1987. Soil and sun angle interactions on
'                  partial canopy spectra: Int. J. Remote Sens, 8:1307-1317.
'            : Rouse, J. W., R. H. Haas, J. A. Schell, and D. W. Deering,
'                  1973. Monitoring Vegetation Systems in the Great Plains
'                  with ERTS, Proceedings, Third ERTS Symposium, Vol. 1,
'                  pp. 48-62.
' Called By  : GUI
' Calls      : None
' Sister Code: None
' ----------------------------------------------------------------------

' Vegetation Index Formulas:

' NDVI = (NIR - red) / (NIR + red)                 [Rouse et al. (1973)]
' SAVI = [(NIR - red) / (NIR + red + L)] * (1 + L) [Huete, 1987]
' TNDVI = (NDVI + 0.5) 1/2                        [Deering et al. (1975)]

' Initialize Variables

ViList = {"NDVI","SAVI","TNDVI"}
AdjustList = {"Automatic Adjustment","Allow Negative Values"}

' Get NIR Grid

NIRSrcList = SourceDialog.ShowClass("Select NIR GRID.",Grid)
If (NIRSrcList.Count = 0) then return NIL end
If (NIRSrcList.Count > 1) then
    msgbox.ERROR("Must Select only one NIR Grid","NIR GRID SELECT ERROR")
    return NIL
End
If (Grid.IsValidDataSetFileName(NIRSrcList.Get(0).GetFileName)) then
  NIRGrid = Grid.Make(NIRSrcList.Get(0))
Else
  msgbox.info("Not A Valid Grid. Please Try Again","NIR GRID ERROR")
  return nil
End
If (NIRGrid.HasError) then
  MsgBox.Error("NIR Grid Has an Error, Exiting","NIR GRID ERROR")
  return Nil
End
  
' Get Red Grid

RedSrcList = SourceDialog.ShowClass("Select RED GRID.",Grid)
If (RedSrcList.Count = 0) then return NIL end
If (RedSrcList.Count > 1) then
    msgbox.ERROR("Must Select only one RED Grid","RED GRID SELECT ERROR")
    return NIL
End
If (Grid.IsValidDataSetFileName(RedSrcList.Get(0).GetFileName)) then
  RedGrid = Grid.Make(RedSrcList.Get(0))
Else
  msgbox.info("Not A Valid Grid. Please Try Again","Red GRID ERROR")
  return nil
End
If (RedGrid.HasError) then
  MsgBox.Error("Red Grid Has an Error, Exiting","RED GRID ERROR")
  return Nil
End

' Get VI selection, Scaling Factor, and Negative Adjustment Option from user

VI = MsgBox.ListAsString(ViList,"Choose VI to Calculate","VI Selection")
If (VI = Nil) then Return Nil End
ScalingFactor = MsgBox.Input("Enter Scaling Factor to Adjust VI","Scaling Factor Input",1.AsString)
If (ScalingFactor = Nil) then Return Nil End
If (ScalingFactor.IsNumber.Not) then
  MsgBox.Info("Scaling Factor is Not a Valid Number, Exiting.","Please Try Again")
  Return Nil
Else
  ScalingFactor = ScalingFactor.AsNumber
End
Adjust = MsgBox.ListAsString(AdjustList,"Enter Negative Value Option"+NL+"(Adjust Negative Values or Allow Negative Values)","Negative Values Option") 
If (Adjust = Nil) then Return Nil End

' Run VI Calculation

If (VI = "NDVI") then
  ViGrid = ((NIRGrid - RedGrid) / (NIRGrid + RedGrid)) * ScalingFactor
ElseIF (VI = "SAVI") then
  L = MsgBox.Input("Enter L factor","SAVI L Factor Input",0.5.AsString)
  If (L = Nil) then Return Nil End
  If (L.IsNumber.Not) then
    MsgBox.Info("L Factor is Not a Valid Number, Exiting.","Please Try Again")
    Return Nil
  Else
    L = L.AsNumber
  End
  ViGrid = (((NIRGrid - RedGrid) / (NIRGrid + RedGrid + L.AsGrid)) * (1.AsGrid + L.AsGrid)) * ScalingFactor
Else  
  ViGrid = ((((NIRGrid - RedGrid) / (NIRGrid + RedGrid)) + 0.5.AsGrid) * 0.5.AsGrid) * ScalingFactor
End

' Check for Negative Value Adjustment, Adjust automatically

If (Adjust = "Automatic Adjustment") then
  ViStatsList = ViGrid.GetStatistics
  ViMin = ViStatsList.Get(0)
  If (ViMin < 0) then
    ViGrid = ViGrid + ViMin.Abs.AsGrid
  End
End


' Save DataSet

ViFN = av.GetProject.GetWorkDir.MakeTmp(VI,"")
If (ViGrid.HasError.Not) then
  ViGrid.SaveDataSet(ViFN)
Else
  MsgBox.Error("Output Grid"++ViFN.AsString++"has an error","ERROR")
End