GetPixel SetPixel DirectX replacement?

[Patrice Terrier]

I am looking for a fast GetPixel/SetPixel replacement.

Do you know if there are any DirectX functions to perform the same purpose?



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Patrice Terrier
mailto[email protected][email protected]</A>

[Chris Boss]

Patrice;

The problem with DirectX functions is that they "don't work" with a regular DC, like the GDI. DirectX has its own method of creating an area to draw on which means you have to use DirectX completely or the GDI completely. Normally, they are not mixed together.

While I have seen a development tool that mixes DirectX and GDI drawing together, this "hybrid" combination of GDI and DirectX is actually slower than either DirectX or GDI alone. A conversion process must be added to make them work together.

Unless you are ready to go 100% DirectX, you will have to stick with the GDI.

I think that when using the GDI, using DIB functions to draw is faster than using SetPixel. SetPixel is terribly slow. Likely the higher GDI functions don't use SetPixel, but another undocumented API call. Functions that draw a line or a Rectangle are always faster than using your own that draw with SetPixel.

Also, don't most "fast" graphic apps draw first to a memory DC and then always BitBlt to the window DC ? Drawing directly to a Windows DC with lower level GDI functions is always slow.


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[Semen Matusovski]

patrice --
don't know about directx, but there is one interesting technique, which i found on codeguru.com (if necessary, i will post links).
you can see this technique in action in http://www.powerbasic.com/support/pb...ad.php?t=22687
(replacement of slowly getpixel).

shortly, idea is following.
imagine that you want to retrieve all pixels of hmem2dc.
1)create dib-section of the same size and select it into hmem1dc.
2) bitblt hmem2dc -> hmem1dc (%srccopy)
after this you can have direct access using bm.bmbits of dib-section.
i should add, that after discussion with florent, it's looks, that it's better to add globallock/unlock for handle of dib-section.

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[Patrice Terrier]

Indeed what I want is to speed up this as much as possible

FUNCTION GetRValue?(BYVAL Colr&)
    FUNCTION = (Colr& AND &H000000FF???)
END FUNCTION

FUNCTION GetGValue?(BYVAL Colr&)
    SHIFT RIGHT Colr&, 8
    FUNCTION = (Colr& AND &H000000FF???)
END FUNCTION

FUNCTION GetBValue?(BYVAL Colr&)
    SHIFT RIGHT Colr&, 16
    FUNCTION = (Colr& AND &H000000FF???)
END FUNCTION

FUNCTION skTransRGB&(BYVAL hDC1&, BYVAL x1&, BYVAL y1&, BYVAL hDC2&, BYVAL x2&, BYVAL y2&, BYVAL Percent&) EXPORT
        
  ' Get the color of the first picture and extract the r&,g&,b& values
    Colr1& = GetPixel(hDC1&, x1&, y1&)
    r1& = GetRValue(Colr1&)
    b1& = GetBValue(Colr1&)
    g1& = GetGValue(Colr1&)
       
  ' Get the color of the second picture and extract the r&,g&,b& values
    Colr2& = GetPixel(hDC2&, x2&, y2&)
    r2& = GetRValue(Colr2&)
    b2& = GetBValue(Colr2&)
    g2& = GetGValue(Colr2&)

  ' Mix the colors based on the specified percent& to create a new color
  ' that's a perfect combination of the previous two
    Complement& = 100 - percent&
    r& = ((Complement& * r1&) + (percent& * r2&)) \ 100
    g& = ((Complement& * g1&) + (percent& * g2&)) \ 100
    b& = ((Complement& * b1&) + (percent& * b2&)) \ 100
    
    FUNCTION = RGB(r&, g&, b&)
        
END FUNCTION

' Performs transluscency
SUB skTransLusBlt(BYVAL hDC&, _
               BYVAL xDest&, BYVAL yDest&, BYVAL nWidth&, BYVAL nHeight&, _
               BYVAL hSrcBMP&, _
               BYVAL xSrc&, BYVAL ySrc&, _
               BYVAL Percent&) EXPORT
'   hDC&           Destination device context
'   xDest&, yDest& Upper-left destination coordinates (pixels)
'   nWidth&        Width of destination
'   nHeight&       Height of destination
'   hSrcBMP&       Handle of the source bitmap
'   xSrc&, ySrc&   Upper-left source coordinates (pixels)
'   Percent&       Tansluscency percentage
'
'   32-Bit Transluscency BitBlt Function
    
    REGISTER x&, y&               

    hSrcDC& = CreateCompatibleDC(hDC&)
    CALL SelectObject(hSrcDC&, hSrcBMP&)
    
    '*'IF TransColor& < 0 THEN TransColor& = GetPixel(hSrcDC&, 0, 0)
    
    ResultDC& = CreateCompatibleDC(hDC&)
    hResultBmp& = CreateCompatibleBitmap(hDC&, nWidth&, nHeight&)
    hDestPrevBmp& = SelectObject(ResultDC&, hResultBmp&)
    CALL BitBlt(ResultDC&, 0, 0, nWidth&, nHeight&, hDC&, xDest&, yDest&, %SRCCOPY)

    '*'WasPercent& = Percent&
    FOR x& = xDest& TO nWidth& - 1
        FOR y& = yDest& TO nHeight& - 1
            '*'IF GetPixel(hSrcDC&, x&, y&) = TransColor& THEN Percent& = 0
            PixelColr& = skTransRGB(hDC&, x&, y&, hSrcDC&, x&, y&, Percent&)
            CALL SetPixel(ResultDC&, x&, y&, PixelColr&)
            '*'Percent& = WasPercent&
        NEXT
    NEXT

  ' Display transparent bitmap on background.
    CALL BitBlt(hDC&, xDest&, yDest&, nWidth&, nHeight&, ResultDC&, 0, 0, %SRCCOPY)

  ' Select original objects back.
    CALL SelectObject(ResultDC&, hDestPrevBmp&)

  ' Deallocate system resources.
    CALL DeleteObject(hResultBmp&)
    CALL DeleteDC(ResultDC&)
    CALL DeleteDC(hSrcDC&)

END SUB

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Patrice Terrier
mailto[email protected][email protected]</A>

[This message has been edited by Patrice Terrier (edited June 15, 2000).]

[Eric Pearson]

Patrice --

If speed is more important than anything else, you might compare your SHIFT-based functions to these:

FUNCTION GetRValue?(BYVAL Colr&)
    FUNCTION = (Colr& AND &h0000FF&)
END FUNCTION
FUNCTION GetGValue?(BYVAL Colr&)
    FUNCTION = (Colr& AND &h00FF00&) \ &h100&
END FUNCTION
FUNCTION GetBValue?(BYVAL Colr&)
    FUNCTION = (Colr& AND &hFF0000&) \ &h10000&
END FUNCTION

I think they'll be faster, according to my old notes.

For that matter, I'd get rid of the functions altogether, at least in the speed-critical sections of code. Hard-code the AND operations where you need them, to avoid the speed penalty of calling a function. This is especially true because your functions are returning BYTE values, which are handled more slowly than LONGs.

Also, have you looked at the SetPixelV function? It is faster than SetPixel, and since you are not using the return value anyway, you may as well use SetPixelV.

-- Eric



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Perfect Sync: Perfect Sync Development Tools
Email: mailto:[email protected][email protected]</A>

[Eric Pearson]

Patrice --

If you really want to go "industrial strength"...

Instead of getting and processing the pixels one by one, you might consider using the GetDIBits API to get the two bitmaps and place them into two buffers where you can access the pixels as LONG values. If I'm not mistaken (it's been a while since I used GetDIBits) you can specify the data format that you want the API to put in the buffers, so you would be able to use LONGs regardless of the color depth of the display.

Once you have two buffers that contain the bitmaps, you could go crazy with the processing. Use pointers, or whatever you need to do, to optimize for speed. Then when all of the pixels have been processed, BitBlt them as a block to the visible DC.

I'm making it sound easier than it is. {G} GetDIBits can be a nightmare to work with. But once you got it working, it should fly compared to get-pixel-draw-pixel. At least theoretically...

-- Eric

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Perfect Sync: Perfect Sync Development Tools
Email: mailto:[email protected][email protected]</A>

[Patrice Terrier]

Eric --

I have used also assembly to speed-up things but I don't feel comfortable with it

I will also try to use SetPixelV.

FUNCTION GetBValue?(BYVAL nColor&) EXPORT
DIM F AS INTEGER
! mov AL, Byte Ptr nColor&[2]
! xor AH, AH
! mov F, AX
FUNCTION = CBYT(F)
END FUNCTION
FUNCTION GetGValue?(BYVAL nColor&) EXPORT
DIM F AS INTEGER
! mov AL, Byte Ptr nColor&[1]
! xor AH, AH
! mov F, AX
FUNCTION = CBYT(F)
END FUNCTION
FUNCTION GetRValue?(BYVAL nColor&) EXPORT
DIM F AS INTEGER
! mov AL, Byte Ptr nColor&[0]
! xor AH, AH
! mov F, AX
FUNCTION = CBYT(F)
END FUNCTION

Thanks to all of you for your suggestions !


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Patrice Terrier
mailto[email protected][email protected]</A>

[Chris Boss]

Patrice;

SetPixelV is definitely faster than SetPixel. SetPixel "returns" the actual color value used (which may be different than the color requested), whereas SetPixelV does not. This means less processing , so it is faster.

SetPixel likely was never intended for fast graphics drawing, pixel by pixel. The optimum way to draw pixel by pixel is to do it in a memory DC using DIBs and then BitBlt it back into the Windows DC.

If you must draw directly into the Windows DC, pixel by pixel, then try using the LineTo function and when ever the number of pixels of the same color is > 1 you will get a speed increase because of drawing multiple pixels at once.


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[Patrice Terrier]

Chris --

>>Try using the LineTo function and when ever the number of pixels of the same color is > 1 you will get a speed increase because of drawing multiple pixels at once.

Using "LineTo" in order to perform a run length of pixels could not be used in most situation because the function must match pixels from 2 distincts DC that do not use linear colors.

Among things, I plan to use transluscency to produce a perfect shadow behind any type of WinLIFT's windows.

If you want I can send you a example (with source code) of my TRANSLUS demo program, this will help you to understand the effect I want to perform, and why I need it to be very fast.







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Patrice Terrier
mailto[email protected][email protected]</A>

[Semen Matusovski]

Patrice --
try this.
Of course, for "industrial" purpose, it's necessary to use Assembler in cycles.

   #Compile Exe
   #Register None
   #Dim All
   #Include "win32api.inc"
   #Resource "gt1.pbr" ' #1 #2
   
   Function MixColor (hWndDst As Long, hWndSrc1 As Long, hWndSrc2 As Long, percent As Long) As Long
      Register i As Long, j As Long
      Dim k As Long, p1 As Long, p2 As Long
      Dim rc As RECT, pWidth As Long, pHeight As Long
      Dim hWnd(2) As Long, Bm(2) As BITMAP, hTmpBmp(2) As Long, hDC(2) As Long, hTmpDC(2) As Long
      Dim bmi As BITMAPINFO, pBits0 As Byte Ptr, pBits1 As Byte Ptr, pBits2 As Byte Ptr
      
      hWnd(0) = hWndDst: hWnd(1) = hWndSrc1: hWnd(2) = hWndSrc2
      For k = 2 To 0 Step -1
         hDC(k) = GetDC(hWnd(k))
         hTmpDC(k) = CreateCompatibleDC (hDC(k))
         If k = 2 Then
            GetClientRect hWnd(k), rc
            pWidth = rc.nRight - rc.nLeft
            pHeight = rc.nBottom - rc.nTop
            bmi.bmiHeader.biSize = SizeOf(bmi.bmiHeader)
            bmi.bmiHeader.biWidth = pWidth
            bmi.bmiHeader.biHeight = pHeight
            bmi.bmiHeader.biPlanes = 1
            bmi.bmiHeader.biBitCount = 32
            bmi.bmiHeader.biCompression = %BI_RGB
         End If
         hTmpBmp(k) = CreateDIBSection(hTmpDC(k), bmi, %DIB_RGB_COLORS, 0, 0, 0)
         GlobalLock hTmpBmp(k): SelectObject hTmpDC(k), hTmpBmp(k)
         If k <> 0 Then BitBlt hTmpDC(k), 0, 0, pWidth, pHeight, hDC(k), 0, 0, %SRCCOPY
         GetObject hTmpBmp(k), SizeOf(bm(k)), bm(k)
         If k = 0 Then pBits0 = bm(k).bmBits Else _
         If k = 1 Then pBits1 = bm(k).bmBits Else pBits2 = bm(k).bmBits
         p1 = 100 - percent: p2 = percent
         If k = 0 Then
            For j = pHeight - 1 To 0 Step - 1
               For i = 0 To pWidth - 1
                  @pBits0[2] = ((p1 * @pBits1[2] + p2 * @pBits2[2])) \ 100
                  @pBits0[1] = ((p1 * @pBits1[1] + p2 * @pBits2[1])) \ 100
                  @pBits0[0] = ((p1 * @pBits1[0] + p2 * @pBits2[0])) \ 100
                  pBits0 = pBits0 + 4: pBits1 = pBits1 + 4: pBits2 = pBits2 + 4
               Next
            Next
            BitBlt hDC(k), 0, 0, pWidth, pHeight, hTmpDC(k), 0, 0, %SRCCOPY
         End If
      Next
      For k = 0 To 2: ReleaseDC hWnd(k), hDC(k): DeleteDC hTmpDC(k): _
         DeleteObject hTmpBmp(k): Next
   End Function
  
   CallBack Function DlgProc
      Select Case CbMsg
         Dim t1 As Single, t2 As Single
         Case %WM_COMMAND
            If CbCtl = 104 Then
               t1 = Timer
               MixColor GetDlgItem(CbHndl, 103), GetDlgItem(CbHndl, 101), _
                        GetDlgItem(CbHndl, 102), 40
               t2 = Timer
               SetWindowText CbHndl, Format$(1000 * (t2 - t1), "# ms")
            End If
      End Select
   End Function

   Function PbMain
      Dim hDlg As Long
      Dialog New 0, "", , , 420, 400, %WS_CAPTION Or %WS_SYSMENU To hDlg
      Control Add ImageX, hDlg, 101, "#1", 10, 10,  400, 100
      Control Add ImageX, hDlg, 102, "#2", 10, 120, 400, 100
      Control Add Label, hDlg, 103, "", 10, 240, 400, 100
      Control Add Button, hDlg, 104, "Mix", 10, 360, 400, 15
      Dialog Show Modal hDlg Call DlgProc
   End Function

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[Patrice Terrier]

Semen --

The full source code of the demo has been posted to you.
I will try your code as soon as I can.

Looks like you have a permanent link to this forum

Thank you.

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Patrice Terrier
mailto[email protected][email protected]</A>

[Tom Hanlin]

GetPixel and SetPixel are inherently inefficient. There's a fair amount of overhead involved in making an API call. For pixel operations, where you're liable to have a great many pixels, you will get the most significant improvements by bypassing these operations altogether. Optimizing relatively fast local operations like GetRValue is not going to have any noticeable effect until you get rid of the real bottleneck. The suggestions here to get a DIB and deal with it directly are fully sensible.

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Tom Hanlin
PowerBASIC Staff

[Patrice Terrier]

Hi all of you.

Thank you everybody for your suggestions.

Things are already done using DIB and pointers, the overall speed is now very good, thus this thread is over.



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Patrice Terrier
mailto[email protected][email protected]</A>