DllStructSetData issue

November 5, 2008

Hi Folks,

I have a problem with DllStructSetData(), it says after a few correct settings that the Array is out of range, but I don't understand why !

The loop seems to be OK, but it although throws an error after a few cycles ...

I've marked the "critical section" like this:

;*********** Here's the problem ****************
     For $y = 0 To $ulBitmapHeight
        For $x = 1 To $ulBitmapWidth
             DllStructSetData ($stBits, 1, 0x000000FF,  $x + ($y * $ulBitmapWidth)); oO ???
         Next
     Next
;***********************************************

#Region                 Alpha Blending a Bitmap

;    The following code sample divides a window into three horizontal areas.
;    Then it draws an alpha-blended bitmap in each of the window areas as follows: 

;       * In the top area, constant alpha = 50% but there is no source alpha. 

#include <WindowsConstants.au3>
#include <WinAPI.au3>

Global Const $tagBITMAPINFOHEADER = 'dword Size;' & _
                                    'long Width;' & _
                                    'long Height;' & _
                                    'ushort Planes;' & _
                                    'ushort BitCount;' & _
                                    'dword Compression;' & _
                                    'dword SizeImage;' & _
                                    'long XPelsPerMeter;' & _
                                    'long YPelsPerMeter;' & _
                                    'dword ClrUsed;' & _
                                    'dword ClrImportant;'

Global Const $tagPAINTSTRUCT    =   'hwnd hDC;' & _
                                    'int  fErase;' & _
                                    'long rcPaint[4];' & _
                                    'int  fRestore;' & _
                                    'int  fIncUpdate;' & _
                                    'byte rgbReserved[32]'
Global $NULL = Ptr (0)
Global Const $DIB_RGB_COLORS = 0
; Blending
Global Const $AC_SRC_OVER   = 0x00
Global Const $AC_SRC_ALPHA   = 0x01

Global Const $BI_RGB    = 0

; Fensterstile
Global Const $WS_EX_COMPOSITED = 0x2000000  ; Gegen "Flackern"

; Nachricht zum Zeichnen abfangen.
GUIRegisterMsg ($WM_PAINT, 'MY_WM_PAINT')

; Das übliche ...
$hWnd = GUICreate ('AlphaBlend - Demo', 400, 350, -1, -1, _
                    $WS_OVERLAPPEDWINDOW, $WS_EX_COMPOSITED)
GUISetBkColor (0xFFFFFF, $hWnd)

GUISetState (@SW_SHOW)


While True
    
    Switch GUIGetMsg ()
        Case -3
            ExitLoop
    EndSwitch
WEnd


Func MY_WM_PAINT ($hWnd, $msg, $lParam, $wParam)
    
     Local $hDC, $ps, $lpPs

    ; Zeichenstruktur erzeugen
     $ps   = DllStructCreate ($tagPAINTSTRUCT)
     $lpPs = DllStructGetPtr ($ps)
     
    ; Gerätekontext wird in WM_PAINT von BeginPaint zurückgegeben
     $hDC = BeginPaint ($hWnd, $lpPs)
     
     DrawAlphaBlend ($hWnd, $hDC)
    
    ; Am Ende von WM_PAINT muss der Gerätekontext
    ; mit EndPaint wieder freigegeben werden !
     EndPaint ($hWnd, $lpPs)
     Return

EndFunc

Func DrawAlphaBlend ($hWnd, $hdcwnd)

; http://msdn.microsoft.com/en-us/library/ms532295(VS.85).aspx
     Local $hdc;          handle of the DC we will create
     Local $hbitmap;      bitmap handle
     Local $bf   = DllStructCreate ($tagBLENDFUNCTION); structure for alpha blending
     Local $bmi = DllStructCreate ($tagBITMAPINFO); bitmap header
     Local $pvBits = DllStructCreate ('ptr pvBits') ;   pointer to DIB section
     Local $ulWindowWidth, $ulWindowHeight;   window width/height
     Local $ulBitmapWidth, $ulBitmapHeight;   bitmap width/height
     Local $rt;          used for getting window dimensions
     Local $x, $y;        stepping variables
     Local $ubAlpha;        used for doing transparent gradient
     Local $ubRed
     Local $ubGreen
     Local $ubBlue
     Local $fAlphaFactor;   used to do premultiply
    
    
   ; get window dimensions
     $rt = _WinAPI_GetClientRect ($hWnd)
     $rtLeft    = DllStructGetData ($rt, "Left")
     $rtTop  = DllStructGetData ($rt, "Top")
     $rtRight   = DllStructGetData ($rt, "Right")
     $rtBottom  = DllStructGetData ($rt, "Bottom")

   ; calculate window width/height
     $ulWindowWidth  = $rtRight  - $rtLeft
     $ulWindowHeight = $rtBottom - $rtTop

   ; make sure we have at least some window size
     If ((Not $ulWindowWidth) Or (Not $ulWindowHeight)) Then _
         Return
         
   ; divide the window into 3 horizontal areas
     $ulWindowHeight = $ulWindowHeight / 3

   ; create a DC for our bitmap -- the source DC for AlphaBlend
     $hdc = _WinAPI_CreateCompatibleDC ($hdcwnd)

     $ulBitmapWidth  = $ulWindowWidth  - ($ulWindowWidth  / 5) * 2
     $ulBitmapHeight = $ulWindowHeight - ($ulWindowHeight / 5) * 2


   ; setup bitmap info
   ; set the bitmap width and height to 60% of the width and height of each of the three horizontal areas. Later on, the blending will occur in the center of each of the three areas.
     DllStructSetData ($bmi, 'Size' ,      DllStructGetSize (DllStructCreate ($tagBITMAPINFOHEADER)))
     DllStructSetData ($bmi, 'Width',      $ulBitmapWidth)
     DllStructSetData ($bmi, 'Height',    $ulBitmapHeight)
     DllStructSetData ($bmi, 'Planes',    1)
     DllStructSetData ($bmi, 'BitCount',    32 );  four 8-bit components
     DllStructSetData ($bmi, 'Compression', $BI_RGB)
     DllStructSetData ($bmi, 'SizeImage',   $ulBitmapWidth * $ulBitmapHeight * 4)

   ; create our DIB section and select the bitmap into the DC
     $hbitmap = CreateDIBSection ($hdc, DllStructGetPtr ($bmi), $DIB_RGB_COLORS, DllStructGetPtr ($pvBits), $NULL, 0x0)
     _WinAPI_SelectObject ($hdc, $hbitmap)

    $stBits = DllStructCreate ('uint[' & DllStructGetData ($bmi, 'Width') _ 
                                       * DllStructGetData ($bmi, 'Height') & ']', DllStructGetPtr ($pvBits))

   ; in top window area, constant alpha = 50%, but no source alpha
   ; the color format for each pixel is 0xaarrggbb
   ; set all pixels to blue and set source alpha to zero
    
;*********** Here's the problem ****************
     For $y = 0 To $ulBitmapHeight
        For $x = 1 To $ulBitmapWidth
             DllStructSetData ($stBits, 1, 0x000000FF,  $x + ($y * $ulBitmapWidth)); oO ???
         Next
     Next
;***********************************************
    
     DllStructSetData ($bf, 'Op'    , $AC_SRC_OVER)
     DllStructSetData ($bf, 'Flags' , 0)
     DllStructSetData ($bf, 'Alpha' , 0x7F);  half of 0xff = 50% transparency
     DllStructSetData ($bf, 'Format', 0);   ignore source alpha channel

     If (Not AlphaBlend ($hdcwnd, $ulWindowWidth / 5, $ulWindowHeight / 5, _
                         $ulBitmapWidth, $ulBitmapHeight, _
                         $hdc, 0, 0, $ulBitmapWidth, $ulBitmapHeight, $bf)) Then _
         Return;     // alpha blend failed
    
   ; do cleanup
     _WinAPI_DeleteObject ($hbitmap)
     _WinAPI_DeleteDC ($hdc)


EndFunc


;***********************************************************************
;*      The funky Funcs ...

Func AlphaBlend ($hdcDest, $nXOriginDest, $nYOriginDest, $nWidthDest, $nHeightDest, _
                         $hdcSrc,  $nXOriginSrc,  $nYOriginSrc,  $nWidthSrc,  $nHeightSrc, ByRef $blendFunction )
    
    Local $aRes = DllCall ('msimg32.dll', 'int', 'AlphaBlend', _
                                                'ptr', $hdcDest,      _ ;  // handle to destination DC
                                                'int', $nXOriginDest, _ ;  // x-coord of upper-left corner
                                                'int', $nYOriginDest, _ ;  // y-coord of upper-left corner
                                                'int', $nWidthDest,   _ ;  // destination width
                                                'int', $nHeightDest,  _ ;  // destination height
                                                'ptr', $hdcSrc,    _ ;  // handle to source DC
                                                'int', $nXOriginSrc,  _ ;  // x-coord of upper-left corner
                                                'int', $nYOriginSrc,  _ ;  // y-coord of upper-left corner
                                                'int', $nWidthSrc,  _ ;  // source width
                                                'int', $nHeightSrc,   _ ;  // source height
                                                'ptr', $blendFunction)  ;  // alpha-blending function
    Return $aRes[0]

EndFunc

Func CreateDIBSection ($hdc, $pbmi, $iUsage, $ppvBits, $hSection, $dwOffset)

    Local $aRes = DllCall('gdi32.dll', 'ptr', 'CreateDIBSection', _
                                            'ptr',   $hdc,    _; // handle to DC
                                            'ptr',   $pbmi,  _; // bitmap data
                                            'uint',  $iUsage,   _; // data type indicator
                                            'ptr*',  $ppvBits,  _; // bit values
                                            'ptr',   $hSection, _; // handle to file mapping object
                                            'dword', $dwOffset ) ; // offset to bitmap bit values
    Return $aRes[0]
    
EndFunc


Func BeginPaint($hWnd, $lpPaint)
    
    Local $aResult = DllCall('user32.dll', 'hwnd', 'BeginPaint', 'hwnd', $hWnd, 'ptr', $lpPaint)
    Return $aResult[0]
    
EndFunc

Func EndPaint($hWnd, $lpPaint)
    
    Local $aResult = DllCall('user32.dll', 'int', 'EndPaint', 'hwnd', $hWnd, 'ptr', $lpPaint)
    Return $aResult[0]
    
EndFunc


#EndRegion
;***************************************************************************

Thanks a lot for audience/patience ...

Greetz

Greenhorn

Edited November 5, 2008 by Greenhorn

November 5, 2008

Hi Folks,

I have a problem with DllStructSetData(), it says after a few correct settings that the Array is out of range, but I don't understand why !

The loop seems to be OK, but it although throws an error after a few cycles ...

I've marked the "critical section" like this:

;*********** Here's the problem ****************
     For $y = 0 To $ulBitmapHeight
        For $x = 1 To $ulBitmapWidth
             DllStructSetData ($stBits, 1, 0x000000FF,  $x + ($y * $ulBitmapWidth)); oO ???
         Next
     Next
;***********************************************

; ... <snip>

    $stBits = DllStructCreate ('uint[' & DllStructGetData ($bmi, 'Width') _ 
                                       * DllStructGetData ($bmi, 'Height') & ']', DllStructGetPtr ($pvBits))

 ; in top window area, constant alpha = 50%, but no source alpha
 ; the color format for each pixel is 0xaarrggbb
 ; set all pixels to blue and set source alpha to zero
    
;*********** Here's the problem ****************
     For $y = 0 To $ulBitmapHeight
        For $x = 1 To $ulBitmapWidth
             DllStructSetData ($stBits, 1, 0x000000FF,  $x + ($y * $ulBitmapWidth)); oO ???
         Next
     Next
;***********************************************

; ... <snip>

Thanks a lot for audience/patience ...

Greetz

Greenhorn

So you created the array with size = DllStructGetData($bmi, 'Width') * DllStructGetData($bmi, 'Height'). What did that come out to? Are you checking it?

Then you access the array at index = $x + ($y * $ulBitmapWidth). What did that come out to? Are you checking it?

Put some error handling in your function to check how those values are coming out.

:mellow:

Edited November 5, 2008 by PsaltyDS

November 5, 2008

So you created the array with size = DllStructGetData($bmi, 'Width') * DllStructGetData($bmi, 'Height'). What did that come out to? Are you checking it?

Then you access the array at index = $x + ($y * $ulBitmapWidth). What did that come out to? Are you checking it?

Put some error handling in your function to check how those values are coming out.

I forgot to copy back the "- 1" in the first For/Next loop, sorry. (my test script is a desaster in the moment ... )

But even then it will fail ...

So, I set in the double-loop the bit values for every pixel, right ?

Doing this by scanning each bitmap line in $y and setting the values in the array with $x, which I have to multiplicate with the length of one line in the bitmap, because, for example, if the bitmap has a size of 250x150 pixels, pixel 0, 1 is at array index 251 ($x=1 + ($y=1 *$ulBitmapWidth), pixel 0, 2 is at array index 501($x=1 + ($y=2 *$ulBitmapWidth), right ?

I did the error handling, the size of the struct is 67200 bytes, the same like $ulBitmapWidth * $ulBitmapHeight * 4(bytes), so it's OK ... *brooding*

...

EDIT:

Always after the 13th setting commes the error ... :mellow:

If I read out the values in the loop it's no error, but the script also fails ...

;*********** Here's the problem ****************
     For $y = 0 To $ulBitmapHeight - 1
        For $x = 1 To $ulBitmapWidth
             DllStructSetData ($stBits, 1, 0x000000FF, $x + ($y * $ulBitmapWidth)); oO ???
            ;DllStructGetData ($stBits, 1, $x + ($y * $ulBitmapWidth)); oO ???
             if @error then ConsoleWrite ('Index : '&$x + ($y * $ulBitmapWidth)&'; Error : '&@error&@crlf)
         Next
     Next
;***********************************************

Greetz

Greenhorn

Edited November 5, 2008 by Greenhorn

November 5, 2008

I forgot to copy back the "- 1" in the first For/Next loop, sorry. (my test script is a desaster in the moment ... )

But even then it will fail ...

So, I set in the double-loop the bit values for every pixel, right ?
Doing this by scanning each bitmap line in $y and setting the values in the array with $x, which I have to multiplicate with the length of one line in the bitmap, because, for example, if the bitmap has a size of 250x150 pixels, pixel 0, 1 is at array index 251 ($x=1 + ($y=1 *$ulBitmapWidth), pixel 0, 2 is at array index 501($x=1 + ($y=2 *$ulBitmapWidth), right ?

Careful how you do that. Pixel numbering is 0-based (there is a pixel at 0,0). AutoIt arrays are 0-based, which is why so many For/Next loops have that -1 in there. But DLL struct arrays are 1-based. There is no DLL struct array element at [0]. So pixel 0,0 is at [1]. That's $x=0 and $y=0, so index = $x + 1 + ($y * $ulBitmapWidth). Pixel 0,1 is at 251 like you indicated.

I did the error handling, the size of the struct is 67200 bytes, the same like $ulBitmapWidth * $ulBitmapHeight * 4(bytes), so it's OK ... *brooding*

...

EDIT:
Always after the 13th setting commes the error ...
If I read out the values in the loop it's no error, but the script also fails ...
;*********** Here's the problem ****************
     For $y = 0 To $ulBitmapHeight - 1
        For $x = 1 To $ulBitmapWidth
             DllStructSetData ($stBits, 1, 0x000000FF, $x + ($y * $ulBitmapWidth)); oO ???
    ;DllStructGetData ($stBits, 1, $x + ($y * $ulBitmapWidth)); oO ???
             if @error then ConsoleWrite ('Index : '&$x + ($y * $ulBitmapWidth)&'; Error : '&@error&@crlf)
         Next
     Next
;***********************************************
Greetz
Greenhorn

I meant more like a temporary debug breakpoint:

; ... <snip>

$iArraySize = DllStructGetData($bmi, 'Width') * DllStructGetData($bmi, 'Height')
$stBits = DllStructCreate('uint[' & $iArraySize & ']', DllStructGetPtr($pvBits))

; in top window area, constant alpha = 50%, but no source alpha
; the color format for each pixel is 0xaarrggbb
; set all pixels to blue and set source alpha to zero

;*********** Here's the problem ****************
For $y = 0 To $ulBitmapHeight
    For $x = 1 To $ulBitmapWidth
        $iPixelIndex = $x + ($y * $ulBitmapWidth)
        If ($iPixelIndex > 0) And ($iPixelIndex <= $iArraySize) Then
            DllStructSetData($stBits, 1, 0x000000FF, $iPixelIndex)
        Else
            MsgBox(16, "Debug", "Error!  Array index out of bounds:" & @CRLF & _
                    "DllStructGetData($bmi, 'Width') = " & DllStructGetData($bmi, 'Width') & @CRLF & _
                    "DllStructGetData($bmi, 'Height') = " & DllStructGetData($bmi, 'Height') & @CRLF & _
                    "Calculated $iArraySize = " & $iArraySize & @CRLF & _
                    "$x = " & $x & "  $y = " & $y & @CRLF & _
                    "$ulBitmapWidth = " & $ulBitmapWidth & @CRLF & _
                    "Calculated $iPixelIndex = " & $iPixelIndex)
            Exit
        EndIf
    Next
Next
;***********************************************

; ... <snip>

Checking the value of $iPixelIndex will slow it down, so you may not want that in there permanently, but it should pop the MsgBox() with diagnostic info before it crashes for that particular problem.

P.S. I just notice you do your loop with "For $x = 1 To $ulBitmapWidth", which is correct, but above that you have "For $y = 0 To $ulBitmapHeight". Shouldn't that be "For $y = 0 To $ulBitmapHeight - 1"?

:mellow:

Edited November 6, 2008 by PsaltyDS

November 6, 2008

If what you are doing is journey based, a learning exercise, good luck. Looks like headache material. May you have lots of enthusiastic perseverance.

If you want to accomplish a task by any means, the functions from gdiplus.dll are better suited to manipulate 0xAARRGGBB color format.

Example:-

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

Global $GuiSizeX = 500, $GuiSizeY = 500

$hGui = GUICreate("GDIPlus Example", $GuiSizeX, $GuiSizeY)
GUISetState()

_GDIPlus_Startup()
; Create Double Buffer, so doesn't need to be repainted on PAINT-Event
$hGraphicGUI = _GDIPlus_GraphicsCreateFromHWND($hGui)
$hBMPBuff = _GDIPlus_BitmapCreateFromGraphics($GuiSizeX, $GuiSizeY, $hGraphicGUI)
$hGraphic = _GDIPlus_ImageGetGraphicsContext($hBMPBuff)
;End Double Buffer add-in 1 of 3

;Graphics here
_GDIPlus_GraphicsClear($hGraphic, 0xFFFFFFFF)  ; White background 
$hBrush3 = _GDIPlus_BrushCreateSolid(0xFF0000FF) ; 100% opaque Blue, 0% transparency - Alpha channel FF
$hBrush2 = _GDIPlus_BrushCreateSolid(0xA00000FF) ; [(0xA0/0xFF)*100] % opaque, [(0xff-0xA0/0xFF)*100] % transparency
$hBrush1 = _GDIPlus_BrushCreateSolid(0x500000FF) ;
_GDIPlus_GraphicsFillRect($hGraphic, 0, 0, $GuiSizeX, $GuiSizeY / 3, $hBrush1) ; Top third of window
_GDIPlus_GraphicsFillRect($hGraphic, 0, $GuiSizeY / 3, $GuiSizeX, $GuiSizeY / 3, $hBrush2) ; Middle third of GUI
_GDIPlus_GraphicsFillRect($hGraphic, 0, $GuiSizeY * 2 / 3 - 1, $GuiSizeX, $GuiSizeY / 3 + 1, $hBrush3)
;End of graphics

; Double Buffer
GUIRegisterMsg(0xF, "MY_PAINT"); Register PAINT-Event 0x000F = $WM_PAINT (WindowsConstants.au3)
GUIRegisterMsg(0x85, "MY_PAINT") ; $WM_NCPAINT = 0x0085 (WindowsConstants.au3)Restore after Minimize.
_GDIPlus_GraphicsDrawImage($hGraphicGUI, $hBMPBuff, 0, 0)
;End Double Buffer add-on 2 of 3

;To save GUI image, un-comment the next two lines.
;_GDIPlus_ImageSaveToFile($hBMPBuff, @DesktopDir & "\TestWrite1.png")
;ShellExecute(@DesktopDir & "\TestWrite1.png")

While 1
    $msg = GUIGetMsg()
    Switch $msg
        Case $GUI_EVENT_CLOSE
            _GDIPlus_BrushDispose($hBrush1)
            _GDIPlus_BrushDispose($hBrush2)
            _GDIPlus_BrushDispose($hBrush3)
            _GDIPlus_GraphicsDispose($hGraphic)
            _GDIPlus_GraphicsDispose($hGraphicGUI)
            _WinAPI_DeleteObject($hBMPBuff)
            _GDIPlus_Shutdown()
            Exit
    EndSwitch
WEnd

;Func to redraw on PAINT MSG
Func MY_PAINT($hWnd, $msg, $wParam, $lParam)
    ; Check, if the GUI with the Graphic should be repainted
    _GDIPlus_GraphicsDrawImage($hGraphicGUI, $hBMPBuff, 0, 0)
    _WinAPI_RedrawWindow($hGui, "", "", BitOR($RDW_INVALIDATE, $RDW_UPDATENOW, $RDW_FRAME)) ; , $RDW_ALLCHILDREN
    Return $GUI_RUNDEFMSG
EndFunc   ;==>MY_PAINT

November 9, 2008

Thanks to both of you for taking notice and giving advice !

Also thx to Malkey, I've seen this script before in my searches for CreateDIBSection(). But I want to get even this function to run.

It seems I got solved the problems with the Bitmap-Bits pointer.

All return values seem to be OK, but no bitmap is drawn. :mellow:

#Region                 Alpha Blending a Bitmap

;    The following code sample divides a window into three horizontal areas.
;    Then it draws an alpha-blended bitmap in each of the window areas as follows: 

;       * In the top area, constant alpha = 50% but there is no source alpha. 

#include <WindowsConstants.au3>
#include <WinAPI.au3>

Global Const $tagBITMAPINFOHEADER = 'dword Size;' & _
                                    'long Width;' & _
                                    'long Height;' & _
                                    'ushort Planes;' & _
                                    'ushort BitCount;' & _
                                    'dword Compression;' & _
                                    'dword SizeImage;' & _
                                    'long XPelsPerMeter;' & _
                                    'long YPelsPerMeter;' & _
                                    'dword ClrUsed;' & _
                                    'dword ClrImportant;'

Global Const $tagPAINTSTRUCT    =   'hwnd hDC;' & _
                                    'int  fErase;' & _
                                    'long rcPaint[4];' & _
                                    'int  fRestore;' & _
                                    'int  fIncUpdate;' & _
                                    'byte rgbReserved[32]'
Global $NULL = Ptr (0)
Global Const $DIB_RGB_COLORS = 0
; Blending
Global Const $AC_SRC_OVER    = 0x00
Global Const $AC_SRC_ALPHA   = 0x01

Global Const $BI_RGB    = 0

; Fensterstile
Global Const $WS_EX_COMPOSITED = 0x2000000   ; Gegen "Flackern"

; Nachricht zum Zeichnen abfangen.
GUIRegisterMsg ($WM_PAINT, 'MY_WM_PAINT')

; Das übliche ...
$hWnd = GUICreate ('Alpha Blending a Bitmap', 400, 350, -1, -1, _
                    $WS_OVERLAPPEDWINDOW, $WS_EX_COMPOSITED)
GUISetBkColor (0xFFFFFF, $hWnd)

GUISetState (@SW_SHOW)


While True
    
    Switch GUIGetMsg ()
        Case -3
            ExitLoop
    EndSwitch
WEnd


Func MY_WM_PAINT ($hWnd, $msg, $lParam, $wParam)
    
     Local $hDC, $ps, $lpPs

     ; Zeichenstruktur erzeugen
     $ps   = DllStructCreate ($tagPAINTSTRUCT)
     $lpPs = DllStructGetPtr ($ps)
     
     ; Gerätekontext wird in WM_PAINT von BeginPaint zurückgegeben
     $hDC = BeginPaint ($hWnd, $lpPs)
     
     DrawAlphaBlend ($hWnd, $hDC)
    
     ; Am Ende von WM_PAINT muss der Gerätekontext
     ; mit EndPaint wieder freigegeben werden !
     EndPaint ($hWnd, $lpPs)
     Return 0

EndFunc

Func DrawAlphaBlend ($hWnd, $hdcwnd)

    ; http://msdn.microsoft.com/en-us/library/ms532295(VS.85).aspx
     Local $hdc         ; handle of the DC we will create
     Local $hbitmap     ; bitmap handle
     Local $bf     = DllStructCreate ($tagBLENDFUNCTION); structure for alpha blending
     Local $bmi    = DllStructCreate ($tagBITMAPINFO);    bitmap header
     Local $pvBits   ; pointer to DIB section
     Local $ulWindowWidth, $ulWindowHeight  ; window width/height
     Local $ulBitmapWidth, $ulBitmapHeight  ; bitmap width/height
     Local $rt            ; used for getting window dimensions
     Local $x, $y         ; stepping variables
     Local $ubAlpha       ; used for doing transparent gradient
     Local $ubRed
     Local $ubGreen
     Local $ubBlue
     Local $fAlphaFactor  ; used to do premultiply
    
    
    ; get window dimensions
     $rt = _WinAPI_GetClientRect ($hWnd)
     $rtLeft    = DllStructGetData ($rt, "Left")
     $rtTop     = DllStructGetData ($rt, "Top")
     $rtRight   = DllStructGetData ($rt, "Right")
     $rtBottom  = DllStructGetData ($rt, "Bottom")

    ; calculate window width/height
     $ulWindowWidth  = $rtRight  - $rtLeft
     $ulWindowHeight = $rtBottom - $rtTop

    ; make sure we have at least some window size
     If ((Not $ulWindowWidth) Or (Not $ulWindowHeight)) Then _
         Return
         
    ; divide the window into 3 horizontal areas
     $ulWindowHeight = $ulWindowHeight / 3

    ; create a DC for our bitmap -- the source DC for AlphaBlend
     $hdc = _WinAPI_CreateCompatibleDC ($hdcwnd)

     $ulBitmapWidth  = $ulWindowWidth  - ($ulWindowWidth  / 5) * 2
     $ulBitmapHeight = $ulWindowHeight - ($ulWindowHeight / 5) * 2


    ; setup bitmap info
    ; set the bitmap width and height to 60% of the width and height of each of the three horizontal areas.
    ; Later on, the blending will occur in the center of each of the three areas.
     DllStructSetData ($bmi, 'Size' ,       DllStructGetSize (DllStructCreate ($tagBITMAPINFOHEADER)))
     DllStructSetData ($bmi, 'Width',       $ulBitmapWidth)
     DllStructSetData ($bmi, 'Height',      $ulBitmapHeight)
     DllStructSetData ($bmi, 'Planes',      1)
     DllStructSetData ($bmi, 'BitCount',    32) ; four 8-bit components
     DllStructSetData ($bmi, 'Compression', $BI_RGB)
     DllStructSetData ($bmi, 'SizeImage',   $ulBitmapWidth * $ulBitmapHeight * 4)

    ; create our DIB section and select the bitmap into the DC
     $hbitmap = CreateDIBSection ($hdc, DllStructGetPtr ($bmi), $DIB_RGB_COLORS, $pvBits, $NULL, 0x0)
     _WinAPI_SelectObject ($hdc, $hbitmap)

    ; in top window area, constant alpha = 50%, but no source alpha
    ; the color format for each pixel is 0xaarrggbb
    ; set all pixels to blue and set source alpha to zero
     For $y = 0 To $ulBitmapHeight - 1
        For $x = 1 To $ulBitmapWidth
             DllStructSetData ($pvBits, 1, 0x000000FF, $x + ($y * $ulBitmapWidth))
         Next
     Next


     DllStructSetData ($bf, 'Op'    , $AC_SRC_OVER)
     DllStructSetData ($bf, 'Flags' , 0)
     DllStructSetData ($bf, 'Alpha' , 0x7F) ;  half of 0xff = 50% transparency
     DllStructSetData ($bf, 'Format', 0)    ;  ignore source alpha channel

     If (Not AlphaBlend ($hdcwnd, $ulWindowWidth / 5, $ulWindowHeight / 5, _
                         $ulBitmapWidth, $ulBitmapHeight, _
                         $hdc, 0, 0, $ulBitmapWidth, $ulBitmapHeight, $bf)) Then _
         Return ;  alpha blend failed
    
    ; do cleanup
     _WinAPI_DeleteObject ($hbitmap)
     _WinAPI_DeleteDC ($hdc)


EndFunc


;***********************************************************************
;*        The funky Funcs ...

Func AlphaBlend ($hdcDest, $nXOriginDest, $nYOriginDest, $nWidthDest, $nHeightDest, _
                 $hdcSrc,  $nXOriginSrc,  $nYOriginSrc,  $nWidthSrc,  $nHeightSrc, ByRef $blendFunction )
    
    Local $aRes = DllCall ('msimg32.dll', 'int', 'AlphaBlend', _
                                                    'ptr', $hdcDest,      _  ;  // handle to destination DC
                                                    'int', $nXOriginDest, _  ;  // x-coord of upper-left corner
                                                    'int', $nYOriginDest, _  ;  // y-coord of upper-left corner
                                                    'int', $nWidthDest,   _  ;  // destination width
                                                    'int', $nHeightDest,  _  ;  // destination height
                                                    'ptr', $hdcSrc,       _  ;  // handle to source DC
                                                    'int', $nXOriginSrc,  _  ;  // x-coord of upper-left corner
                                                    'int', $nYOriginSrc,  _  ;  // y-coord of upper-left corner
                                                    'int', $nWidthSrc,    _  ;  // source width
                                                    'int', $nHeightSrc,   _  ;  // source height
                                                    'ptr', $blendFunction)   ;  // alpha-blending function
    Return $aRes[0]

EndFunc

Func CreateDIBSection ($hdc, $pbmi, $iUsage, ByRef $ppvBits, $hSection, $dwOffset)

    Local $aRes = DllCall('gdi32.dll', 'ptr', 'CreateDIBSection', _
                                                'ptr',   $hdc,      _ ; // handle to DC
                                                'ptr',   $pbmi,     _ ; // bitmap data
                                                'uint',  $iUsage,   _ ; // data type indicator
                                                'ptr*',  $ppvBits,  _ ; // bit values
                                                'ptr',   $hSection, _ ; // handle to file mapping object
                                                'dword', $dwOffset )  ; // offset to bitmap bit values
    Local $cbSize = DllStructGetData (DllStructCreate ($tagBITMAPINFOHEADER, $pbmi), 'SizeImage')
    $ppvBits = DllStructCreate ('uint[' & $cbSize / 4 & ']', $aRes[4])
    Return $aRes[0]
    
EndFunc


Func BeginPaint($hWnd, $lpPaint)
    
    Local $aResult = DllCall('user32.dll', 'hwnd', 'BeginPaint', 'hwnd', $hWnd, 'ptr', $lpPaint)
    Return $aResult[0]
    
EndFunc

Func EndPaint($hWnd, $lpPaint)
    
    Local $aResult = DllCall('user32.dll', 'int', 'EndPaint', 'hwnd', $hWnd, 'ptr', $lpPaint)
    Return $aResult[0]
    
EndFunc


#EndRegion
;***************************************************************************

Does somebody have any suggestions ?

Greetz

Greenhorn

Edited November 9, 2008 by Greenhorn

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DllStructSetData issue

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