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VB 5/6-Tipp 0253: Helligkeit und Kontrast einer 24-Bit Bitmap ändern

 von ActiveVB

Schwierigkeitsgrad:

Verwendete API-Aufrufe: BitBlt, RtlMoveMemory (CopyMemory), GetObjectA (GetObject), VarPtr (VarPtrArray)

Download: Download des Beispielprojektes [30,99 KB]

'Dieser Quellcode stammt von http://www.activevb.de
'und kann frei verwendet werden. Für eventuelle Schäden
'wird nicht gehaftet.

'Um Fehler oder Fragen zu klären, nutzen Sie bitte unser Forum.
'Ansonsten viel Spaß und Erfolg mit diesem Source!

'------------- Anfang Projektdatei Project1.vbp -------------
'--------- Anfang Formular "Form1" alias Form1.frm  ---------
' Steuerelement: Horizontale Scrollbar "HScroll2"
' Steuerelement: Horizontale Scrollbar "HScroll1"
' Steuerelement: Bildfeld-Steuerelement "Picture1"
' Steuerelement: Bildfeld-Steuerelement "Picture2"
' Steuerelement: Beschriftungsfeld "Label2"
' Steuerelement: Beschriftungsfeld "Label1"


'Der Tip wird erst zur .exe kompiliert zum wahren Genuß!

Option Explicit

Private Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As _
        Long, ByVal x As Long, ByVal y As Long, ByVal nWidth _
        As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, _
        ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As _
        Long) As Long

Private Declare Function GetObject Lib "gdi32" Alias _
        "GetObjectA" (ByVal hObject As Long, ByVal nCount As _
        Long, lpObject As Any) As Long

Private Declare Function VarPtrArray Lib "msvbvm50.dll" Alias _
        "VarPtr" (Ptr() As Any) As Long

Private Declare Sub CopyMemory Lib "kernel32" Alias _
        "RtlMoveMemory" (pDst As Any, pSrc As Any, ByVal _
        ByteLen As Long)

Private Type SAFEARRAYBOUND
  cElements As Long
  lLbound As Long
End Type

Private Type SAFEARRAY1D
  cDims As Integer
  fFeatures As Integer
  cbElements As Long
  cLocks As Long
  pvData As Long
  Bounds(0 To 0) As SAFEARRAYBOUND
End Type

Private Type SAFEARRAY2D
  cDims As Integer
  fFeatures As Integer
  cbElements As Long
  cLocks As Long
  pvData As Long
  Bounds(0 To 1) As SAFEARRAYBOUND
End Type


Private Type BITMAP
  bmType As Long
  bmWidth As Long
  bmHeight As Long
  bmWidthBytes As Long
  bmPlanes As Integer
  bmBitsPixel As Integer
  bmBits As Long
End Type

Private Const SRCCOPY = &HCC0020

Dim Brightness!, Contrast!
Dim TableBright(255) As Byte


Private Sub Form_Load()
  Picture1.Picture = LoadPicture(App.Path & "\Bild.jpg")
  Picture2.Picture = LoadPicture(App.Path & "\Bild.jpg")
End Sub

Private Sub HScroll1_Change()
  Dim x%, Temp!
  
    Brightness = Exp(HScroll1.Value / 50) / 5 - 0.2

    For x = 0 To 255
      Temp = x * Brightness
      If Temp > 255 Then Temp = 255
      TableBright(x) = Temp
    Next
    
    Call MakeBitmap
    Picture1.Refresh
End Sub

Private Sub HScroll2_Change()
  Dim x%, Temp!
  
    Contrast = Exp(HScroll2.Value / 30) / 20 - 0.05

    For x = 0 To 255
      Temp = ((x - 127) * Contrast) + 127
      If Temp > 255 Then Temp = 255
      If Temp < 0 Then Temp = 0
      TableBright(x) = Temp
    Next x
    
    Call MakeBitmap
    Picture1.Refresh
End Sub

Private Sub MakeBitmap()
  Dim Pic() As Byte, PicBuff() As Byte
  Dim SA As SAFEARRAY2D, Bmp As BITMAP
  Dim SABuff As SAFEARRAY2D, BmpBuff As BITMAP
  Dim x%, y%

    Call GetObject(Picture1.Picture, Len(Bmp), Bmp)
    Call GetObject(Picture2.Picture, Len(BmpBuff), BmpBuff)
  
    If Bmp.bmBitsPixel <> 24 Then
      MsgBox "Es werden nur 24-Bit Bitmaps unterstützt!"
      Exit Sub
    End If
    
    With SA
      .cbElements = 1
      .cDims = 2
      .Bounds(0).lLbound = 0
      .Bounds(0).cElements = Bmp.bmHeight
      .Bounds(1).lLbound = 0
      .Bounds(1).cElements = Bmp.bmWidthBytes
      .pvData = Bmp.bmBits
    End With
    
    Call CopyMemory(ByVal VarPtrArray(Pic), VarPtr(SA), 4)
        
    With SABuff
      .cbElements = 1
      .cDims = 2
      .Bounds(0).lLbound = 0
      .Bounds(0).cElements = BmpBuff.bmHeight
      .Bounds(1).lLbound = 0
      .Bounds(1).cElements = BmpBuff.bmWidthBytes
      .pvData = BmpBuff.bmBits
    End With
    
    Call CopyMemory(ByVal VarPtrArray(PicBuff), VarPtr(SABuff), 4)
    
    For x = 0 To UBound(Pic, 1)
      For y = 0 To UBound(Pic, 2)
        Pic(x, y) = TableBright(PicBuff(x, y))
      Next y
    Next x

    Call CopyMemory(ByVal VarPtrArray(Pic), 0&, 4)
    Call CopyMemory(ByVal VarPtrArray(PicBuff), 0&, 4)
End Sub
'---------- Ende Formular "Form1" alias Form1.frm  ----------
'-------------- Ende Projektdatei Project1.vbp --------------

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