Option Explicit
Private Declare Function CreateDIBSection Lib "gdi32" (ByVal hDC As Long, pBitmapInfo As BITMAPINFO24, ByVal un As Long, lplpVoid As Long, ByVal handle As Long, ByVal dw As Long) As Long
Private Declare Function GetDC Lib "user32" (ByVal hWnd As Long) As Long
Private Declare Function CreateCompatibleDC Lib "gdi32" (ByVal hDC As Long) As Long
Private Declare Function ReleaseDC Lib "user32" (ByVal hWnd As Long, ByVal hDC As Long) As Long
Private Declare Function SelectObject Lib "gdi32" (ByVal hDC As Long, ByVal hObject As Long) As Long
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 DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Private Declare Function DeleteDC Lib "gdi32" (ByVal hDC As Long) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (Destination As Any, Source As Any, ByVal Length As Long)
Private Declare Function VarPtrArray Lib "msvbvm60.dll" Alias "VarPtr" (Ptr() As Any) As Long
 
Private Type RGBQUAD
    rgbBlue As Byte
    rgbGreen As Byte
    rgbRed As Byte
    rgbReserved As Byte
End Type
 
Private Type BITMAPINFOHEADER
    biSize As Long
    biWidth As Long
    biHeight As Long
    biPlanes As Integer
    biBitCount As Integer
    biCompression As Long
    biSizeImage As Long
    biXPelsPerMeter As Long
    biYPelsPerMeter As Long
    biClrUsed As Long
    biClrImportant As Long
End Type
 
Private Type BITMAPINFO24
    bmiHeader As BITMAPINFOHEADER
    bmiColors() As RGBQUAD
End Type
 
Private Type SAFEARRAYBOUND
    cElements As Long
    lLbound As Long
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 Const DIB_RGB_COLORS = 0
Private Const BI_RGB = 0&
 
 
Public Sub BuscarContornos(Pic As PictureBox)
    Dim BytesPerLine As Long
    Dim WinDC As Long
    Dim TmpDC As Long
    Dim hBmp As Long
    Dim OldBmp As Long
    Dim Addrs As Long
    Dim X As Long
    Dim Y As Long
    Dim lpBits() As Byte
    Dim M_BitmapInfo As BITMAPINFO24
    Dim SA As SAFEARRAY2D
    Dim R As Byte, G As Byte, B As Byte
 
    BytesPerLine = ScanAlign(Pic.ScaleWidth * 3)
 
    With M_BitmapInfo.bmiHeader
        .biSize = Len(M_BitmapInfo.bmiHeader)
        .biWidth = Pic.ScaleWidth
        .biHeight = Pic.ScaleHeight
        .biPlanes = 1
        .biBitCount = 24
        .biCompression = BI_RGB
        .biSizeImage = BytesPerLine * Pic.ScaleHeight
    End With
 
    WinDC = GetDC(0)
    TmpDC = CreateCompatibleDC(WinDC)
    hBmp = CreateDIBSection(WinDC, M_BitmapInfo, DIB_RGB_COLORS, Addrs, 0, 0)
 
    Call ReleaseDC(0, WinDC)
 
    With SA
        .cbElements = 1
        .cDims = 2
        .Bounds(0).lLbound = 0
        .Bounds(0).cElements = Pic.ScaleHeight
        .Bounds(1).lLbound = 0
        .Bounds(1).cElements = BytesPerLine
        .pvData = Addrs
    End With
 
    CopyMemory ByVal VarPtrArray(lpBits), VarPtr(SA), 4
 
    OldBmp = SelectObject(TmpDC, hBmp)
 
    Call BitBlt(TmpDC, 0, 0, Pic.ScaleWidth, Pic.ScaleHeight, Pic.hDC, 0, 0, vbSrcCopy)
 
    For Y = 0 To Pic.ScaleHeight - 1
        For X = 0 To (Pic.ScaleWidth * 3) - 1 Step 3
 
            B = lpBits(X + 2, Y)
            G = lpBits(X + 1, Y)
            R = lpBits(X, Y)
 
            '----------------------------------
            '
            'Aca modificas el R,G,B a tu gusto
            '
            '----------------------------------
 
            lpBits(X, Y) = R
            lpBits(X + 1, Y) = G
            lpBits(X + 2, Y) = B
 
        Next X
    Next Y
 
    CopyMemory ByVal VarPtrArray(lpBits), 0&, 4
    Call BitBlt(Pic.hDC, 0, 0, Pic.ScaleWidth, Pic.ScaleHeight, TmpDC, 0, 0, vbSrcCopy)
    Call DeleteObject(SelectObject(TmpDC, OldBmp))
    Call DeleteDC(TmpDC)
 
 
 
End Sub
 
Private Function ScanAlign(WidthBmp As Long) As Long
    ScanAlign = (WidthBmp + 3) And &HFFFFFFFC
End Function
 

Private Sub Command1_Click()
    BuscarContornos PicTratamiento
    PicTratamiento.Refresh
End Sub
 
Private Sub Form_Load()
    PicTratamiento.AutoRedraw = True
    PicTratamiento.ScaleMode = vbPixels
End Sub