Public Class Form1
    Public SC As Double, XST As Double, YST As Double, DT As Double
    Public Function Comp(A0 As Double, B0 As Double, C As Double, D As Double) As Integer  ' 収束・発散の計算
        Dim A As Double, B As Double, AA As Double
        Dim BB As Double, DA As Double, DB As Double
        A = A0 : B = B0 : Comp = 100
        For i = 0 To 100
            AA = A : BB = B : Comp = i
            A = AA * AA - BB * BB + C : B = 2 * AA * BB + D
            If A * A + B * B >= 4 Then Exit Function '発散
            DA = A - AA : DB = B - BB
            If DA * DA + DB * DB < 0.001 Then Exit Function '収束
        Next
    End Function
    Private Sub setScale() ' 描画スケール定義
        Dim XED As Double
        XST = Val(TextBox3.Text) : XED = Val(TextBox4.Text)
        YST = Val(TextBox5.Text)
        SC = 200 / (XED - XST) : DT = 1.0 / SC
    End Sub
    Private Sub Draw(XX As Single, YY As Single, N As Integer) ' 色設定を変更してみよう
        Dim g As Graphics = PictureBox1.CreateGraphics()
        Dim CH As Integer, CC As Color, X As Single, Y As Single

        X = (XX - XST) * SC : Y = 100 - (YY - YST) * SC / 2
        CH = (N Mod 5) * 51 : If CH > 255 Then CH = 255
        CC = Color.FromArgb(CH, CH, CH)
        Dim b As New SolidBrush(CC)
        g.FillRectangle(b, X, Y, X + 1, Y + 1)
    End Sub
    Private Sub Mandel()   ' マンデルブロ集合：標準的な初期値は(0,0)とする
        Dim A As Double, B As Double, C As Double, D As Double
        Dim i As Integer, j As Integer, N As Integer, LP As Integer
        Dim g As Graphics = PictureBox1.CreateGraphics()
        A = Val(TextBox1.Text) : B = Val(TextBox2.Text) : DT = Val(TextBox3.Text)
        setScale() : g.Clear(Color.Black) : C = XST - DT
        For i = 0 To 200 : C = C + DT : D = YST - DT
            For j = 0 To 200 : D = D + DT
                N = Comp(A, B, C, D) : Draw(C, D, N)
            Next
        Next
    End Sub
    Private Sub Julia()   ' 充填ジュリア集合
        Dim C As Double, D As Double, i As Integer, j As Integer
        Dim N As Integer, A As Double, B As Double
        Dim g As Graphics = PictureBox1.CreateGraphics()
        C = Val(TextBox1.Text) : D = Val(TextBox2.Text)
        setScale() : g.Clear(Color.Black) : A = XST - DT
        For i = 0 To 200 : A = A + DT : B = YST - DT
            For j = 0 To 200 : B = B + DT
                N = Comp(A, B, C, D) : Draw(A, B, N)
            Next
        Next
       

    End Sub

    Private Sub Button1_Click(sender As System.Object, e As System.EventArgs) Handles Button1.Click
        Mandel()
    End Sub

    Private Sub Button2_Click(sender As System.Object, e As System.EventArgs) Handles Button2.Click
        Julia()
    End Sub
End Class