Нарисовать прямоугольний треугольник. Прошу направить на путь истинный

Imports System.Drawing
Imports System.Drawing.Imaging
 
Public Class Form1
    Dim BMP As Bitmap
 
    Private Sub DrawLine(ByRef bm As Bitmap, ByVal X1 As Integer, ByVal Y1 As Integer, ByVal X2 As Integer, ByVal Y2 As Integer, ByVal C As Color)
        Dim y As Integer
 
        If X1 = X2 Then
            For i As Integer = Y1 To Y2
                bm.SetPixel(X1, i, C)
            Next
        ElseIf Y1 = Y2 Then
            For i As Integer = X1 To X2
                bm.SetPixel(i, Y1, C)
            Next
        Else
            For i As Integer = X1 To X2
                y = ((Y2 - Y1) / (X2 - X1) * i) + Y1
                bm.SetPixel(i, y, C)
            Next
        End If
    End Sub
 
 
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim bm As New Bitmap(PictureBox1.Width, PictureBox1.Height)
        BMP = bm
    End Sub
 
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim X1, X2, Y1, Y2 As Integer
 
        X1 = Xtext.Text
        Y1 = Ytext.Text
        X2 = X1 + Wtext.Text
        Y2 = Y1 + Htext.Text
 
        DrawLine(BMP, X1, Y1, X2, Y2, PictureBox2.BackColor)
        DrawLine(BMP, X1, Y1, X2, Y1, PictureBox2.BackColor)
        DrawLine(BMP, X2, Y1, X2, Y2, PictureBox2.BackColor)
 
        PictureBox1.Image = Nothing
        PictureBox1.Image = BMP
    End Sub
 
    Private Sub PictureBox2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PictureBox2.Click
        If ColorDialog1.ShowDialog = Windows.Forms.DialogResult.OK Then
            sender.Backcolor = ColorDialog1.Color
        End If
    End Sub
 
    Private Sub Wtext_Validating(ByVal sender As System.Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles Wtext.Validating, Htext.Validating
        If Not IsNumeric(sender.text) Then
            e.Cancel = True : Exit Sub
        End If
        If sender.text < 1 Or sender.text > 250 Then
            e.Cancel = True : Exit Sub
        End If
    End Sub
 
 
    Private Sub Xtext_Validating(ByVal sender As System.Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles Xtext.Validating, Ytext.Validating
        If Not IsNumeric(sender.text) Then
            e.Cancel = True : Exit Sub
        End If
        If sender.text < 0 Or sender.text > 250 Then
            e.Cancel = True : Exit Sub
        End If
    End Sub

Imports System.Drawing
Imports System.Drawing.Imaging
Public Class Form1
    Dim BMP As Bitmap
    Private Sub DrawLine(ByRef bm As Bitmap, ByVal pnt1 As PointF, ByVal pnt2 As PointF, ByVal c As Color)
        Dim i As Integer
        Const N = 500
        Dim dx As Double = (pnt2.X - pnt1.X) / N
        Dim dy As Double = (pnt2.Y - pnt1.Y) / N
        Dim X1 As Double = pnt1.X
        Dim Y1 As Double = pnt1.Y
        For i = 0 To N
            Dim X As Double = X1 + dx * i
            Dim Y As Double = Y1 + dy * i
            Try
                bm.SetPixel(X, Y, c)
            Catch ex As Exception
                'MsgBox(ex.ToString)
            End Try
        Next
    End Sub
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
        If OpenFileDialog1.ShowDialog = Windows.Forms.DialogResult.OK Then
            Dim bm As New Bitmap(OpenFileDialog1.FileName)
            Dim bm1 As New Bitmap(bm, Button1.Width, Button1.Height)
            Button1.Text = ""
            Button1.BackgroundImage = bm1
        End If
    End Sub
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        OpenFileDialog1.Filter = "*.jpg|*.jpg|*.bmp|*.bmp|*.png|*.png"
        OpenFileDialog1.FilterIndex = 1
        OpenFileDialog1.FileName = ""
        Dim bm As New Bitmap(PictureBox1.Width, PictureBox1.Height)
        BMP = bm
    End Sub
    Private Sub Button2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button2.Click
        Dim pnt1 As PointF
        Dim pnt2 As PointF
        Dim pnt3 As PointF
        BMP = New Bitmap(PictureBox1.Width, PictureBox1.Height)
        pnt1.X = CSng(txtX1.Text)
        pnt1.Y = CSng(txtY1.Text)
        pnt2.X = CSng(txtX2.Text)
        pnt2.Y = CSng(txtY2.Text)
        Dim Alpha As Double
        Alpha = Math.PI / 2 - Math.Atan2((pnt2.X - pnt1.X), (pnt2.Y - pnt1.Y))
        Dim R As Double = txtK1.Text
        pnt3.X = pnt2.X - R * Math.Sin(Alpha)
        pnt3.Y = pnt2.Y + R * Math.Cos(Alpha)
        DrawLine(BMP, pnt1, pnt2, PictureBox2.BackColor)
        DrawLine(BMP, pnt2, pnt3, PictureBox2.BackColor)
        DrawLine(BMP, pnt1, pnt3, PictureBox2.BackColor)
        PictureBox1.Image = Nothing
        PictureBox1.Image = BMP
    End Sub
    Private Sub PictureBox2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles PictureBox2.Click
        If ColorDialog1.ShowDialog = Windows.Forms.DialogResult.OK Then
            sender.Backcolor = ColorDialog1.Color
        End If
    End Sub
    Private Sub txtY1_Validating(ByVal sender As System.Object, ByVal e As System.ComponentModel.CancelEventArgs) Handles txtX2.Validating, txtY2.Validating, _
    txtK1.Validating, txtK2.Validating, txtX1.Validating, txtY1.Validating
        If Not IsNumeric(sender.text) Then
            e.Cancel = True : Exit Sub
        End If
        If sender.text < 0 Or sender.text > 250 Then
            e.Cancel = True : Exit Sub
        End If
    End Sub
End Class