Win2000, 24-bit DIB section

[Semen Matusovski]

Decided to save a memory a little (to use 24 bit DIB section instead of 32 bit) and found something very strange ...

According MSDN, bm.bmWidthBytes should be divisable 2.
I create 24-bit DIB section (hMemBmp), retrive bitmap (GetObject hMemBmp, Len(BITMAP), bm) and then work with scan lines directly.

bm.bmWidth = 31
bm.bmWidthBytes = 94 (as expected, because 31 * 3 = 93)

In calculations I accept that distance beetween scan lines is bm.bmWidthBytes.
All works fine, for example, in 98SE.

But not under Win2000.
If to use DWORD alignment (bm.bmWidthBytes = 96), all works fine here too.
But I see nothing in MSDN about DWORD alignment.
Like idea, Windows by itself should also use original "bm.bmWidthBytes" (means 94 here).

Did somebody notice the same ?


Below is a subroutine, which I debug (analog of FillRect ... CreatePatternBrush, but w/o limit 8*8 pixels).
Change 32 to 24 and you will see troubles under 2000.

   Global gBackground_BmpFile  As String ' <--- name of background bmp-file
   Global gBackground_hBmp As Long

   Sub MemCopy (ByVal Dest As Dword, ByVal Source As Dword, ByVal ln As Dword)

    ! cld
    ! mov esi, Source
    ! mov edi, Dest
    ! mov ecx, ln

    ! shr ecx, 2
    ! rep movsd

    ! mov ecx, ln
    ! And ecx, 3
    ! rep movsb

   End Sub

   Function DrawBackground(hDC As Long, rc As RECT) As Long

      Static gBackground_BmpFile_Old As String, gBackground_hBmp As Long, bmBkg As BITMAP
      Local bmi As BITMAPINFO, hMemBmp As Long, bm As BITMAP, hMem1DC As Long, hMem2DC As Long, rcMem As RECT
      Local i1 As Long, i2 As Long, j1 As Long, j2 As Long
      Local l1 As Long, l2 As Long, l As Long, p1 As Byte Ptr, p2 As Byte Ptr
                                             

      If gBackground_BmpFile_Old <> gBackground_BmpFile Then
         If gBackground_hBmp <> 0 Then DeleteObject gBackground_hBmp: gBackground_hBmp = 0
         gBackground_BmpFile_Old = gBackground_BmpFile

         hMemBmp = LoadImage(ByVal 0, ByVal StrPtr(gBackground_BmpFile), %IMAGE_BITMAP, 0, 0, _
                      %LR_CREATEDIBSECTION Or %LR_DEFAULTSIZE Or %LR_LOADFROMFILE)

         If hmemBmp Then
            hMem1DC = CreateCompatibleDC(hDC)
            hMem2DC = CreateCompatibleDC(hMem1DC)
            GetObject hMemBmp, SizeOf(bm), bm
            bmi.bmiHeader.biSize = SizeOf(bmi.bmiHeader)
            bmi.bmiHeader.biWidth = bm.bmWidth
            bmi.bmiHeader.biHeight = bm.bmHeight
            bmi.bmiHeader.biPlanes = 1
            bmi.bmiHeader.biBitCount = 32
            bmi.bmiHeader.biCompression = %BI_RGB
            gBackground_hBmp = CreateDIBSection(hMem1DC, bmi, %DIB_RGB_COLORS, 0, 0, 0)
            GlobalLock gBackground_hBmp

            SelectObject hMem1DC, hMemBmp
            SelectObject hMem2DC, gBackground_hBmp
            BitBlt hMem2DC, 0, 0, bm.BmWidth, bm.BmHeight, hMem1Dc, 0, 0, %SRCCOPY
            DeleteDC hMem1DC
            DeleteDC hMem2DC
            DeleteObject hMemBmp
            GetObject gBackground_hBmp, Len(BITMAP), bmBkg
         End If
      End If

      rcMem.nLeft = 0
      rcMem.nTop = 0
      rcMem.nRight = rc.nRight - rc.nLeft
      rcMem.nBottom = rc.nBottom - rc.nTop

      hMem1DC = CreateCompatibleDC(hDC)
      bmi.bmiHeader.biSize = SizeOf(bmi.bmiHeader)
      bmi.bmiHeader.biWidth = rcMem.nRight
      bmi.bmiHeader.biHeight = rcMem.nBottom
      bmi.bmiHeader.biPlanes = 1
      bmi.bmiHeader.biBitCount = 32
      bmi.bmiHeader.biCompression = %BI_RGB
      hMemBmp = CreateDIBSection(hMem1DC, bmi, %DIB_RGB_COLORS, 0, 0, 0)
      GlobalLock hMemBmp
      SelectObject hMem1DC, hMemBmp
      GetObject hMemBmp, Len(BITMAP), bm
  
      For j1 = bm.bmHeight - 1 To 0 Step -1
         If j2 = 0 Then j2 = bmBkg.bmHeight
         Decr j2
         p1 = bm.bmBits    + bm.bmWidthBytes    * j1
         p2 = bmBkg.bmBits + bmBkg.bmWidthBytes * j2

         l1 = bm.bmWidthBytes
         l2 = bmBkg.bmWidthBytes

         l = l2
         If l > l1 Then l = l1
         If l > 0 Then MemCopy p1, p2, l
         p2 = p1 + l
         l = l1 - l
         If l > 0 Then MemCopy p2, p1, l

      Next

      If gPalette Then
         SelectPalette hDC, gPalette, 0
         RealizePalette hDC
      End If

      DrawEdge hMem1DC, rcMem, %EDGE_SUNKEN, %BF_RECT
      BitBlt hDC, rc.nLeft, rc.nTop, rc.nRight - rc.nLeft, rc.nBottom - rc.nTop, hMem1Dc, 0, 0, %SRCCOPY
      DeleteObject hMem1DC
      DeleteObject hMemBmp

   End Function

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[This message has been edited by Semen Matusovski (edited October 17, 2001).]

[Jules Marchildon]

"CreatePatternBrush, but w/o limit 8*8 pixels" I thought only for Win95?

I know not exactly your needs, but works well with just plain old bitmap.

'-----------------------------------------------------------------------------
' Tile a bitmap within defined RECT
'
'-----------------------------------------------------------------------------
SUB FillWithBitmap( ByVal dc AS LONG, ByVal hbmp AS LONG, rc AS RECT )
 
    LOCAL w     AS LONG, h  AS LONG
    LOCAL x     AS LONG, y  AS LONG, z AS LONG
    LOCAL bx    AS LONG, by AS LONG
    LOCAL memdc AS LONG
 
    IF ISFALSE(hbmp) THEN EXIT SUB
 
    memdc = CreateCompatibleDC( dc )
    Call SelectObject( memdc, hbmp )
 
    w = rc.nright - rc.nleft
    h = rc.nbottom - rc.ntop
 
    bx = GetBitmapWidth( hbmp )
    by = GetBitmapHeight( hbmp )
 
    y = rc.nTop
    DO WHILE y < h
       IF (y+by) > h THEN by = h-y
       z = bx
       x = rc.nLeft
       DO WHILE x < w
          IF  (x+z) > w THEN z = w-x
          Call BitBlt (dc, x, y, z, by, memdc, 0, 0, %SRCCOPY )
          x = x + z
       LOOP
       y = y + by
    LOOP
    Call DeleteDC( memdc )
END SUB

[Semen Matusovski]

Jules --
I was afraid a lot of BitBlt.
For example, rect size is 1000 * 800, a size of Bmp - 31 * 30.
About 1000 calls.

Compared two methods in different resolutions /color depth.
In some combinations (first of all, 32-bit regime) my method 20-25% faster, but in more typical cases (16/24 bit) - not (because I build big DIB section anyway).

So, I decided do not investigate bicycle and to use BitBlt.
Thanx.



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[Brad D Byrne]

Two quick questions---- Please

Semen, What were you referancing with "bicycle" ?

And, I've been using Compatable Bitmaps---- and they have
been working quite well----What is the advantage of DIB's ?

Thanks, B.

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[Semen Matusovski]

Brad --
At the second part of 19th century a lot of guys offered own models of bicycles - three cycles; one big cycle, another small and so on.
So in Russian language appeared a special termin, which is possible to translate as "to invent a bicycle" and which means to do absurd work, because actually it's impossible to find a bew variant.

I use DIBs to work with pixels directly (as with array of RGB values).
For example, you want to change "brightness". To do this you need to multiply RGB of each pixel per coefficient.
It's possible to do using Get/SetPixel, but these functions are very slowly (imagine a screen of 1024 * 768; 1 mln API calls to get and 1 mln to set).

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E-MAIL: [email protected]

[Torsten Rienow]

Hi Semen,
you should try the following.

'instead of
Local bm as BITMAP
GetObject hMemBmp, SizeOf(bm), bm

'you should
TYPE DIBSECTION
    dsBm                        AS BITMAP
    dsBmih                      AS BITMAPINFOHEADER
    dsBitfields(2)              AS DWORD
    dshSection                  AS DWORD
    dsOffset                    AS DWORD
END TYPE
LOCAL bm as DIBSECTION
GetObject hMemBmp, SizeOf(bm), bm

'And you should also
LOCAL bmBitsPtr AS LONG
gBackground_hBmp = CreateDIBSection(hMem1DC, bmi, %DIB_RGB_COLORS, bmBitsPtr , 0, 0)
'to get a Pointer to the DIB Bits

i am very certain, that this will solve
your problems

regards,

Torsten

P.S.: Short Comment:
Because you are obtaining a BITMAP with GetObjct,
you get a BITMAP wich is DWORD aligned. If you
obtain a DIBSECTION, you get a DIBSECTION wich is
WORD aligned.
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[This message has been edited by Torsten Rienow (edited October 18, 2001).]

[Brad D Byrne]

Interesting,---And Thanks, Semen

Seems I may have been Bicycling my own version of DIB! B.

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