円・楕円を描画するには(塗りつぶしなし)

円・楕円を描画してみます。
キーワードは「Ellipse()関数」です。
Ellipse()関数は円を包含する矩形を指定することで円・楕円を描画する関数です。
矩形を定義するだけで円を描画できるので何かと役に立ちます。

実行時の様子


'円・楕円を描画する
Private Declare Function Ellipse Lib "gdi32.dll" _
    (ByVal hdc As Long, ByVal nLeftRect As Long, ByVal nTopRect As Long, _
    ByVal nRightRect As Long, ByVal nBottomRect As Long) As Long
'現在の位置を変更する
Private Declare Function MoveToEx Lib "gdi32.dll" _
    (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal lpCoord As Long) As Long
Private Type RECT
    x As Long
    y As Long
    dx As Long
    dy As Long
End Type
'矩形の周囲に指定のブラシで境界線を書く
Private Declare Function FrameRect Lib "user32.dll" _
        (ByVal hdc As Long, lpRect As RECT, ByVal hbr As Long) As Long
'デバイスコンテキストにオブジェクトを選択する
Private Declare Function SelectObject Lib "gdi32.dll" _
    (ByVal hdc As Long, ByVal hgdiobj As Long) As Long
'グラフィックスオブジェクトを削除し、システムリソースを開放する
Private Declare Function DeleteObject Lib "gdi32.dll" (ByVal hObject As Long) As Long
'ソリッドカラー(純色）で論理ブラシを作成する
Private Declare Function CreateSolidBrush Lib "gdi32.dll" _
    (ByVal crColor As Long) As Long

 

Private Sub Form_Load()
    Me.Picture1.ScaleMode = 3           'ピクセルモード
End Sub


Private Sub Picture1_Paint()
    Dim lpRect As RECT, hbr As Long, hOld As Long
    With Me.Picture1
        .BackColor = vbWhite            '背景色
        
        '枠線を描画
        lpRect.x = 10
        lpRect.y = 10
        lpRect.dx = .ScaleWidth - 10
        lpRect.dy = .ScaleHeight - 10
        hbr = CreateSolidBrush(RGB(180, 180, 180))
        Call FrameRect(.hdc, lpRect, hbr)
        Call DeleteObject(hbr)
        
        .ForeColor = vbRed             'ペンの色
        '円弧を描画
        Call Ellipse(.hdc, 10, 10, .ScaleWidth - 10, .ScaleHeight - 10)
        
    End With
End Sub

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