ToGreyscale.ahk

; Link:   	
; Author:	
; Date:   	
; for:     	AHK_L

/*


*/

ToGrayscale(sBM) {                            ; By SKAN on CR7J/D39J @ tiny.cc/tograyscale
  Local  ; Original ver. GDI_GrayscaleBitmap() @ https://autohotkey.com/board/topic/82794-
  VarSetCapacity(BM,24,0),  DllCall("GetObject", "Ptr",sBM, "Int",24, "Ptr",&BM)
  W := NumGet(BM,4,"Int"), H := NumGet(BM,8,"Int")
  sDC := DllCall( "CreateCompatibleDC", "Ptr",0, "Ptr")
  DllCall("DeleteObject", "Ptr",DllCall("SelectObject", "Ptr",sDC, "Ptr",sBM, "Ptr"))

  tBM := DllCall( "CopyImage", "Ptr"
       , DllCall( "CreateBitmap", "Int",1, "Int",1, "Int",0x1, "Int",8, "Ptr",0, "Ptr")
       , "Int",0, "Int",W, "Int",H, "Int",0x2008, "Ptr")

  tDC := DllCall("CreateCompatibleDC", "Ptr",0, "Ptr")
  DllCall("DeleteObject", "Ptr",DllCall("SelectObject", "Ptr",tDC, "Ptr",tBM, "Ptr"))

  Loop % (255, n:=0x000000, VarSetCapacity(RGBQUAD256,256*4,0))
        Numput(n+=0x010101, RGBQUAD256, A_Index*4, "Int")
  DllCall("SetDIBColorTable", "Ptr",tDC, "Int",0, "Int",256, "Ptr",&RGBQUAD256)

  DllCall("BitBlt",   "Ptr",tDC, "Int",0, "Int",0, "Int",W, "Int",H
                    , "Ptr",sDC, "Int",0, "Int",0, "Int",0x00CC0020)

Return (tBM, DllCall("DeleteDC", "Ptr",sDC), DllCall("DeleteDC", "Ptr",tDC))
}
;- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

; Demo follows

#NoEnv
#SingleInstance, Force
SetWorkingDir, %A_ScriptDir%

If !FileExist("bluebottlefly.jpg")
   URLDownloadToFile, https://www.autohotkey.com/boards/download/file.php?id=10624
                    , bluebottlefly.jpg

hBM1 := LoadPicture("bluebottlefly.jpg")
hBM2 := ToGrayscale(hBM1)
Gui, Margin, 24, 24
Gui, Add, Picture,,    HBITMAP:%hBM1%
Gui, Add, Picture,x+m, HBITMAP:%hBM2%
Gui, Show,, ToGrayscale()
Return