Option Explicit

'APIの宣言をします
Private Declare Function AlphaBlend Lib "msimg32.dll" _
    (ByVal hDCDest As Long, _
    ByVal nXDest As Long, ByVal nYDest As Long, _
    ByVal nWidthDest As Long, ByVal nHeightDest As Long, _
    ByVal hDCSrc As Long, _
    ByVal nXSrc As Long, ByVal nYSrc As Long, _
    ByVal nWidthSrc As Long, ByVal nHeightSrc As Long, _
    ByVal nBlendFunc As Long) As Long

'フォームをロードします
Private Sub Form_Load()
    'プロパティの設定をします
    Picture1.ScaleMode = vbPixels
    Picture2.ScaleMode = vbPixels
    Picture1.AutoRedraw = True
    Picture2.AutoRedraw = True
End Sub

'開始ボタンを押しました
Private Sub Command1_Click()
    Dim j As Long
    
    '2度押しを防ぐためにEnabedをFalseにします
    Command1.Enabled = False
    
    '描画を開始します
    Picture2.Cls
    Picture2.Refresh
    For j = 0 To 255
        AlphaBlend _
                Picture2.hDC, 0, 0, Picture2.ScaleWidth, Picture2.ScaleHeight _
                , Picture1.hDC, 0, 0, Picture1.ScaleWidth, Picture1.ScaleHeight _
                , j * &H10000
        Picture1.Refresh
        Picture2.Refresh
    Next
    
    Command1.Enabled = True
End Sub