Trage câteva linii pe o imagine cu mouse-ul muta

Question 1

Vreau să atrag câteva linii pe o imagine Folosind mouse-ul muta în vb.net. Problema mea este că atunci când am începe să desenați următoarea linie, linia anterioară dispare! Poate cineva să mă ajute? Mi-am pus cod, împreună cu o fotografie a rula proiectul meu

Dim st, en As New Point
Dim p As Pen
Private mouseButtonPressed As Boolean = False

Private Sub PictureBox1_Paint(sender As Object, e As PaintEventArgs) Handles PictureBox1.Paint
    p = New Pen(Color.Black, 2)
    Dim g As Graphics = e.Graphics
    g.DrawLine(p, st, en)
End Sub

Private Sub PictureBox1_MouseUp(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseUp
    mouseButtonPressed = False
End Sub

Private Sub PictureBox1_MouseMove(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseMove
    If mouseButtonPressed Then
        PictureBox1.Invalidate()
        en = e.Location
    End If
End Sub

Private Sub PictureBox1_MouseDown(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseDown
    If e.Button = MouseButtons.Left Then
        st = New Point(e.X, e.Y)
        mouseButtonPressed = True
    End If
End Sub

GIF of my run project

Question 2

Puteți stoca linii într-o listă ca ei a lua finalizat, apoi trage toate liniile anterioare, atunci când sunt de desen pe cel viu

Private st, en As New Point
Private mouseButtonPressed As Boolean = False

Private lines As New List(Of (st As Point, en As Point))

Private Sub PictureBox1_Paint(sender As Object, e As PaintEventArgs) Handles PictureBox1.Paint
    Dim p = New Pen(Color.Black, 2)
    Dim g As Graphics = e.Graphics
    g.DrawLine(p, st, en)
    For Each line In lines
        g.DrawLine(p, line.st, line.en)
    Next
End Sub

Private Sub PictureBox1_MouseUp(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseUp
    mouseButtonPressed = False
    lines.Add((st, en))
End Sub

Private Sub PictureBox1_MouseMove(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseMove
    If mouseButtonPressed Then
        PictureBox1.Invalidate()
        en = e.Location
    End If
End Sub

Private Sub PictureBox1_MouseDown(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseDown
    If e.Button = MouseButtons.Left Then
        st = New Point(e.X, e.Y)
        mouseButtonPressed = True
    End If
End Sub

Lista deține Tuple(of Point, Point)

djv · Answer 1 · 2021-11-23T15:48:51

Puteți stoca linii într-o listă ca ei a lua finalizat, apoi trage toate liniile anterioare, atunci când sunt de desen pe cel viu

Private st, en As New Point
Private mouseButtonPressed As Boolean = False

Private lines As New List(Of (st As Point, en As Point))

Private Sub PictureBox1_Paint(sender As Object, e As PaintEventArgs) Handles PictureBox1.Paint
    Dim p = New Pen(Color.Black, 2)
    Dim g As Graphics = e.Graphics
    g.DrawLine(p, st, en)
    For Each line In lines
        g.DrawLine(p, line.st, line.en)
    Next
End Sub

Private Sub PictureBox1_MouseUp(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseUp
    mouseButtonPressed = False
    lines.Add((st, en))
End Sub

Private Sub PictureBox1_MouseMove(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseMove
    If mouseButtonPressed Then
        PictureBox1.Invalidate()
        en = e.Location
    End If
End Sub

Private Sub PictureBox1_MouseDown(sender As Object, e As MouseEventArgs) Handles PictureBox1.MouseDown
    If e.Button = MouseButtons.Left Then
        st = New Point(e.X, e.Y)
        mouseButtonPressed = True
    End If
End Sub

Lista deține Tuple(of Point, Point)

Trage câteva linii pe o imagine cu mouse-ul muta

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