Visual Basic Bitmap Routines
ExtFloodFill: Fill Polygonal Regions
     
Posted:   Tuesday January 16, 2001
Updated:   Monday December 26, 2011
     
Applies to:   VB4-32, VB5, VB6
Developed with:   VB4-32, Windows 95
OS restrictions:   None
Author:   VBnet, Tanner Helland
       
 Prerequisites
None.

Here's a quickie one-form demo that shows how to use the ExtFloodFill API to construct a child's drawing canvas that can save and reload a picture.

When the left mouse is pressed, lines are drawn on the picturebox in response to a drag. When the right mouse is pressed, a random colour fills the interior of the bounded shape. If the mouse is over the lines, they change colour instead. The code is based on the "Simple Paint and Fill Demo" by Tanner Helland.

 BAS Module Code
None.

 Form Code
Add two command buttons (Command1, Command2) to a form along with the following code:

Option Explicit
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Copyright 1996-2011 VBnet/Randy Birch, All Rights Reserved.
' Some pages may also contain other copyrights by the author.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' Distribution: You can freely use this code in your own
'               applications, but you may not reproduce 
'               or publish this code on any web site,
'               online service, or distribute as source 
'               on any media without express permission.
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Option Explicit
         
Private Declare Function ExtFloodFill Lib "Gdi32" _
  (ByVal hdc As Long, _
   ByVal X As Long, _
   ByVal Y As Long, _
   ByVal crColor As Long, _
   ByVal wFillType As Long) As Long
   
'variables used for drawing and filling
Dim X1 As Single
Dim Y1 As Single
Dim bDraw As Boolean


Private Sub Form_Load()

  'used to create a random fill colour
   Randomize Time
   
  'initialize picturebox 
   With Picture1
     .AutoRedraw = True
     .ScaleMode = vbPixels
     .FillStyle = vbFSSolid
   End With
       
End Sub


Private Sub Form_Resize()

   Picture1.Move 120, 600, Me.ScaleWidth - 240, Me.ScaleHeight - 1300
   
End Sub


Private Sub Command1_Click()

   On Error Resume Next
   
   With CommonDialog1
      .CancelError = True
      .Flags = cdlOFNExplorer Or cdlOFNFileMustExist Or cdlOFNLongNames
      .Filter = "*.bmp|*.bmp"
      .ShowOpen
      
      If Len(.FileName) > 0 Then
         Picture1.Picture = LoadPicture(.FileName)
      End If
      
   End With
      
load_exit:
   Exit Sub
   
load_error:
   Resume load_exit
   
End Sub


Private Sub Command2_Click()

   On Error Resume Next
   
   With CommonDialog1
      .CancelError = True
      .Flags = cdlOFNExplorer Or cdlOFNFileMustExist Or cdlOFNLongNames
      .Filter = "*.bmp|*.bmp"
      .ShowSave
      
      If Len(.FileName) > 0 Then
         SavePicture Picture1.Image, .FileName
      End If
      
   End With
      
save_exit:
   Exit Sub
   
save_error:
   Resume save_exit
   
End Sub


Private Sub Picture1_MouseDown(Button As Integer, Shift As Integer, X As Single, Y As Single)

  'enable drawing
   bDraw = True
   
  'if left mouse button, set up the line drawing
   If Button = vbLeftButton Then
   
      X1 = X
      Y1 = Y
   
  'if right mouse button, fill
   ElseIf Button = vbRightButton Then
      
       Picture1.FillColor = RGB(Int(Rnd * 255), Int(Rnd * 255), Int(Rnd * 255))
       ExtFloodFill Picture1.hdc, X, Y, Picture1.Point(X, Y), 1
       
   End If
   
End Sub


Private Sub Picture1_MouseMove(Button As Integer, Shift As Integer, X As Single, Y As Single)

  'if left mouse button, draw a
  'line between the original point
  'and the current one, but only
  'if drawing is enabled
   If bDraw Then
      If Button = vbLeftButton Then
      
         Picture1.Line (X1, Y1)-(X, Y)
         X1 = X
         Y1 = Y
         
      End If
      
   End If

End Sub

Private Sub Picture1_MouseUp(Button As Integer, Shift As Integer, X As Single, Y As Single)

  'disable drawing
   bDraw = False
   
End Sub
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