GDIPlus with 4-bit graphics?

[a440hz]

I can't seem to get it.

I'm trying to create a 720 x 480 bitmap mask for a DVD menu subpicture. For my purposes, this must be done invisibly and saved as a 4 bit png.

I'm able to create an empty bitmap, fill it with white and create black button boxes. The problem is that the result can only be saved as 32 bit color. I don't know how to either convert to 4 bit before saving or how to work in 4 bit color space top begin with.

_GDIPlus_BitmapCloneArea does not appear to allow conversion between different color bit depths.

I also tried creating a blank white 4 bit image in Photoshop and opening it with GDI but the result is still a 32bit file. I don't see a way to work with RGB brushes instead of ARGB.

Here's a sample of my code. If anyone can point me in the right direction I would be extremely thankful.

-a440Hz

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#include <GDIPlus.au3>
#include <WinAPI.au3>

Global $hWnd, $hDC, $hBitmap1, $hImage1, $hGraphics1, $hBrush
Global $ARGB, $RGB, $Alpha
Global $DVDWidth = 720
Global $DVDHeight = 480
Global $DVDBgColor = "0xFFFFFF"
Global $DVDBgAlpha = "FF"
Global $DVDButtonColor = "0x000000"
Global $SafeArea = 0.1
Global $DVDButtonHeight = 24
Global $DVDButtonSpacing = 2
Global $DVDTitleVerticalOffset = 48

; Start GDI+ library
_GDIPlus_Startup ()

;Create DVD Menu Background
$hWnd = _WinAPI_GetDesktopWindow ()
$hDC = _WinAPI_GetDC ($hWnd)
$hBitmap1 = _WinAPI_CreateCompatibleBitmap ($hDC, $DVDWidth, $DVDHeight)
_WinAPI_ReleaseDC ($hWnd, $hDC)

;Draw Background
$hImage1 = _GDIPlus_BitmapCreateFromHBITMAP ($hBitmap1)
$hGraphics1 = _GDIPlus_ImageGetGraphicsContext ($hImage1)

;Fill With Solid White  
$hBrush = _GDIPlus_BrushCreateSolid (_Color($DVDBgColor,$DVDBgAlpha))
_GDIPlus_GraphicsFillRect ($hGraphics1,0, 0, $DVDWidth, $DVDHeight,$hBrush) 

;Create greatest number of button masks (normally would be the number of songs) 
$hBrush = _GDIPlus_BrushCreateSolid (_Color($DVDButtonColor,$DVDBgAlpha))
For $i = 1 to 15
    _GDIPlus_GraphicsFillRect ($hGraphics1,($DVDWidth * $SafeArea)/2, _
    ($i * ($DVDButtonHeight + $DVDButtonSpacing)) + $DVDTitleVerticalOffset, $DVDWidth-($DVDWidth * $SafeArea), $DVDButtonHeight)   
Next    

; Save DVD Menu Mask
_GDIPlus_ImageSaveToFile ($hImage1, @ScriptDir & "\track_menu_mask.png")    

; Clean up resources
_GDIPlus_ImageDispose ($hImage1)    
_GDIPlus_BrushDispose ($hBrush)
_WinAPI_DeleteObject ($hBitmap1)
_GDIPlus_GraphicsDispose ($hGraphics1)


; Shut down GDI+ library
_GDIPlus_ShutDown ()



Func _Color($RGB,$Alpha)
    $ARGB = StringLeft($RGB,2) & $Alpha & StringRight($RGB,6)
    Return $ARGB
EndFunc

Edited April 5, 2009 by a440hz