Module1

Public Declare Function GetObjectAPI Lib "gdi32" Alias "GetObjectA" (ByVal hObject As Long, ByVal nCount As Long, lpObject As Any) As Long

Public Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long

Public Declare Function SetWindowRgn Lib "user32" (ByVal hwnd As Long, ByVal hRgn As Long, ByVal bRedraw As Boolean) As Long

Public Declare Function CreateRectRgn Lib "gdi32" (ByVal X1 As Long, ByVal Y1 As Long, ByVal X2 As Long, ByVal Y2 As Long) As Long

Public Declare Function CombineRgn Lib "gdi32" (ByVal hDestRgn As Long, ByVal hSrcRgn1 As Long, ByVal hSrcRgn2 As Long, ByVal nCombineMode As Long) As Long

Public Const RGN_OR = 2

Public Declare Function GetBitmapBits Lib "gdi32" (ByVal hBitmap As Long, ByVal dwCount As Long, lpBits As Any) As Long

Public Type BITMAP '14 bytes
bmType As Long
bmWidth As Long
bmHeight As Long
bmWidthBytes As Long
bmPlanes As Integer
bmBitsPixel As Integer
bmBits As Long
End Type

Dim bmByte() As Byte

Public Declare Function ReleaseCapture Lib "user32" () As Long

Public Declare Function SendMessage Lib "user32" Alias "SendMessageA" (ByVal hwnd As Long, ByVal wMsg As Long, ByVal wParam As Long, lParam As Any) As Long

'Public Const WM_SYSCOMMAND = &H112
'Public Const SC_MOVE = &HF012
Public Const HTCAPTION = 2
Public Const WM_NCLBUTTONDOWN = &HA1

Public Sub SetAutoRgn(hForm As Form, Optional transColor As Byte = vbNull)
Dim X As Long, Y As Long
Dim Rgn1 As Long, Rgn2 As Long
Dim SPos As Long, EPos As Long
Dim bm As BITMAP
Dim hbm As Long
Dim Wid As Long, Hgt As Long
Dim xoff As Long, yoff As Long

hbm = hForm.Picture
GetObjectAPI hbm, Len(bm), bm
Wid = bm.bmWidth
Hgt = bm.bmHeight

ReDim bmByte(1 To Wid, 1 To Hgt)
GetBitmapBits hbm, Wid * Hgt, bmByte(1, 1) 獲取圖像數組

If transColor = vbNull Then transColor = bmByte(1, 1)

Rgn1 = CreateRectRgn(0, 0, 0, 0)

For Y = 1 To Hgt 逐行掃描
X = 0
Do
X = X + 1

While (bmByte(X, Y) = transColor) And (X < Wid)
X = X + 1 跳過是透明色的點
Wend
SPos = X
While (bmByte(X, Y) <> transColor) And (X < Wid)
X = X + 1 跳過不是透明色的點
Wend
EPos = X - 1

'這一段是合并區域
If SPos <= EPos Then
Rgn2 = CreateRectRgn(SPos - 1, Y - 1, EPos, Y)
CombineRgn Rgn1, Rgn1, Rgn2, RGN_OR
DeleteObject Rgn2
End If
Loop Until X >= Wid
Next Y

SetWindowRgn hForm.hwnd, Rgn1, True 設定窗體形狀區域
DeleteObject Rgn1

End Sub

Form1

Private Sub Form_Load()

Form1.Left = Screen.Width / 2 - Form1.Width / 2
Form1.Top = Screen.Height / 2 - Form1.Height / 2

If Me.Picture <> 0 Then Call SetAutoRgn(Me)

End Sub

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

If Button = vbLeftButton Then
ReleaseCapture
SendMessage Me.hwnd, WM_NCLBUTTONDOWN, HTCAPTION, 0&

End If
End Sub