AutoHotkey Community

Gui, Add, Button, Default gButtonSelectFont, Press this to show font-picker dialog
Gui, Add, Text, w60 right xm, RGB Color:
Gui, Add, Edit, x+10 ReadOnly vColor

; Most of the setup for the font picker dialog needs to be done only once,
; which is why this section is here rather than in the button's subroutine.
/*
typedef struct tagCHOOSECOLOR {
  DWORD lStructSize;
  HWND hwndOwner;
  HINSTANCE hInstance;
  COLORREF rgbResult;
  COLORREF* lpCustColors;
  DWORD Flags;
  LPARAM lCustData;
  LPCCHOOKPROC lpfnHook;
  LPCTSTR lpTemplateName;
} CHOOSECOLOR, *LPCHOOSECOLOR;
*/
SizeOfStructForChooseColor = 0x24
VarSetCapacity(StructForChooseColor, SizeOfStructForChooseColor, 0)
VarSetCapacity(StructArrayForChooseColor, 64, 0)

Gui, +LastFound
GuiHWND := WinExist()  ; Relies on the line above to get the unique ID of GUI window.

InsertInteger(SizeOfStructForChooseColor, StructForChooseColor, 0)  ; DWORD lStructSize
InsertInteger(GuiHWND, StructForChooseColor, 4)  ; HWND hwndOwner (makes dialog "modal").
InsertInteger(0x0 ,    StructForChooseColor, 8)  ; HINSTANCE hInstance
InsertInteger(0x0 ,    StructForChooseColor, 12)  ; clr.rgbResult =  0;
InsertInteger(&StructArrayForChooseColor , StructForChooseColor, 16)  ; COLORREF *lpCustColors
InsertInteger(0x00000100 , StructForChooseColor, 20)  ; Flag: Anycolor
InsertInteger(0x0 ,    StructForChooseColor, 24)  ; LPARAM lCustData
InsertInteger(0x0 ,    StructForChooseColor, 28)  ; LPCCHOOKPROC lpfnHook
InsertInteger(0x0 ,    StructForChooseColor, 32)  ; LPCTSTR lpTemplateName


Gui, Show
return

ButtonSelectFont:
nRC := DllCall("comdlg32\ChooseColorA", str, StructForChooseColor)  ; Display the dialog.
if (errorlevel <> 0) || (nRC = 0)
{
   MsgBox error while calling ChooseColor Errorlevel: %errorlevel% - RC: %nRC%
   return
}

; Otherwise, the user pressed OK in the dialog, so determine what was selected.
;GuiControl,, Color, % BGRtoRGB(ExtractInteger(StructForChooseColor, 12))
SetFormat, integer, hex  ; Show RGB color extracted below in hex format.
GuiControl,, Color, % BGRtoRGB(ExtractInteger(StructForChooseColor, 12))
SetFormat, integer, d
return

#h::reload

GuiClose:
ExitApp

ExtractInteger(ByRef pSource, pOffset = 0, pIsSigned = false, pSize = 4)
; See DllCall documentation for details.
{
   SourceAddress := &pSource + pOffset  ; Get address and apply the caller's offset.
   result := 0  ; Init prior to accumulation in the loop.
   Loop %pSize%  ; For each byte in the integer:
   {
      result := result | (*SourceAddress << 8 * (A_Index - 1))  ; Build the integer from its bytes.
      SourceAddress += 1  ; Move on to the next byte.
   }
   if (!pIsSigned OR pSize > 4 OR result < 0x80000000)
      return result  ; Signed vs. unsigned doesn't matter in these cases.
   ; Otherwise, convert the value (now known to be 32-bit) to its signed counterpart:
   return -(0xFFFFFFFF - result + 1)
}

InsertInteger(pInteger, ByRef pDest, pOffset = 0, pSize = 4)
; To preserve any existing contents in pDest, only pSize number of bytes starting at
; pOffset are altered in it. The caller must ensure that pDest has sufficient capacity.
{
   mask := 0xFF  ; This serves to isolate each byte, one by one.
   Loop %pSize%  ; Copy each byte in the integer into the structure as raw binary data.
   {
      DllCall("RtlFillMemory", UInt, &pDest + pOffset + A_Index - 1, UInt, 1  ; Write one byte.
         , UChar, (pInteger & mask) >> 8 * (A_Index - 1))  ; This line is auto-merged with above at load-time.
      mask := mask << 8  ; Set it up for isolation of the next byte.
   }
}

BGRtoRGB(oldValue)
{
  Value := (oldValue & 0x00ff00)
  Value += ((oldValue & 0xff0000) >> 16)
  Value += ((oldValue & 0x0000ff) << 16) 
  return Value
}
return

MsgBox, % ChooseColor() 

ChooseColor( Color=0x0, hWnd=0x0, Flags=0x2 )  { ; CC_FULLOPEN := 0x2
 VarSetCapacity(CC,36+64,0), NumPut(36,CC), NumPut(hWnd,CC,4), NumPut(Color,CC,12)
 NumPut(&CC+36,CC,16), NumPut(Flags,CC,20), DllCall( "comdlg32\ChooseColorA", Str,CC )
 Return NumGet(CC,12,"UChar") "." NumGet(CC,13,"UChar") "." NumGet(CC,14,"UChar")   
}

MsgBox, % ChooseColorH() 

ChooseColorH( Color=0x0, hWnd=0x0, Flags=0x2 )  { ; CC_FULLOPEN := 0x2
 VarSetCapacity(CC,36+64,0), NumPut(36,CC), NumPut(hWnd,CC,4), NumPut(Color,CC,12)
 NumPut(&CC+36,CC,16), NumPut(Flags,CC,20), DllCall( "comdlg32\ChooseColorA", Str,CC )
 Hex:="123456789ABCDEF0",   RGB:=&CC+11
 Loop 3 
  HexColorCode .=  SubStr(Hex, (*++RGB >> 4), 1) . SubStr(Hex, (*RGB & 15), 1)
Return HexColorCode 
}

Gui, 99:+LastFound
Gui, 99:Show, w453 h324 Hide
hwnd := WinExist()
MsgBox, % ChooseColorH( 0x0, hwnd )

ChooseColorH( Color=0x0, hWnd=0x0, Flags=0x2 )  { ; CC_FULLOPEN := 0x2
 VarSetCapacity(CC,36+64,0), NumPut(36,CC), NumPut(hWnd,CC,4), NumPut(Color,CC,12)
 NumPut(&CC+36,CC,16), NumPut(Flags,CC,20), DllCall( "comdlg32\ChooseColorA", Str,CC )
 Hex:="123456789ABCDEF0",   RGB:=&CC+11
 Loop 3
  HexColorCode .=  SubStr(Hex, (*++RGB >> 4), 1) . SubStr(Hex, (*RGB & 15), 1)
Return HexColorCode
}

; Example:
; Start with some random colors (optional)
Col:=0xFF0000
CColors:=Object()
Loop 16
  CColors.Insert(A_Index,A_Index*1036335)

If ChooseColor(Col,CColors)=1
{
  SetFormat, Integer, HEX
  b:=Col
  a:="Chosen: " b "`r`nCustom:`r`n"
  Loop 16
  a .= A_Index ": " CColors[A_Index] "`r`n"
  MsgBox, %a%
}
else Msgbox, Cancel!

; Function:

ChooseColor( ByRef Color, ByRef CustColors, hWnd=0x0, Flags=0x103 )
{
;  CC_FULLOPEN := 0x2  CC_RGBINIT := 0x1
  VarSetCapacity(CC,36+64,0)
  NumPut(36,CC)
  NumPut(hWnd,CC,4)
  NumPut(Color,CC,12)
  Loop 16
    NumPut(CustColors[A_Index],CC,32+A_Index*4)
  NumPut(&CC+36,CC,16)
  NumPut(Flags,CC,20)
  RVal:=DllCall( "comdlg32\ChooseColorW", Str,CC )
  Color:=NumGet(CC,12,"UInt")
  CustColors:=
  CustColors:=Object()
  Loop 16
  {
    CustColors.Insert(A_Index,Numget(CC,32+A_Index*4,"UInt"))
  }
  Return RVal ; 1 if OK; 0 if Cancel or Closed
}