Solved

Draw a circle that follows the mouse cursor without latent circles

Posted on 2009-03-31
4
941 Views
Last Modified: 2013-12-17
I have a form and would like to have a circle follow the mouse cursor.  Similarly to what is shown in Adobe Photoshop when you are in line brush mode and you can see the size of the brush you are about to draw.  My problem occurs when I place a background image on the form.

To use the example code below.  Create form and paste the code into the form (the size of my form is 804X584).  Run the application.  Initially you will have great performance.  However if you give the form a background image.  In my situation I just used C:\Documents and Settings\All Users\Documents\My Pictures\Sample Pictures\Blue hills.jpg and you will see some latent circles when you move the mouse very fast.  The attached picture shows you the latent circles.

I've tried using the OvalShape from Microsoft.VisualBasic.PowerPacks but the performance of that was even worse.

Some notes about the code below:
1.  I pretty draw the circle in the function ShowQualityCircle (called from MouseMove).  Here I call Invalidate without any arguments.  When I tried it with a rectangle I got a number of latent circles.  I even tried a larger rectangles but when I moved the mouse very fast I still got latent circles.
2.  Without the call to draw the circle in the Paint routine I got a number of latent rectangles, so that was necessary.

You help would be greatly appreciated.

Public Class Form1

  Private QCircle As New Rectangle(0, 0, 0, 0)
 

  Private Sub Form1_MouseMove(ByVal sender As Object, ByVal e As System.Windows.Forms.MouseEventArgs) Handles Me.MouseMove

    ShowQualityCircle((e.X), (e.Y), 20)

  End Sub
 

  Private Sub Form1_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles Me.Paint

    If QCircle.Width > 0 AndAlso QCircle.Height > 0 Then

      DrawCircle(e.Graphics, Color.Red, QCircle.X, QCircle.Y, QCircle.Width, QCircle.Height, 0, 360)

    End If

  End Sub
 

  Private Sub DrawCircle(ByRef g As Graphics, ByVal currentColor As Color, ByVal x As Single, ByVal y As Single, ByVal width As Single, ByVal height As Single, ByVal startAngle As Single, ByVal sweepAngle As Single)

    Dim myBrush As New SolidBrush(currentColor)

    Dim myPen As New Pen(myBrush)

    myPen.Width = 1

    g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias

    g.DrawArc(myPen, x, y, width, height, startAngle, sweepAngle)

  End Sub
 

  Private Sub ShowQualityCircle(ByVal imgX As Integer, ByVal imgY As Integer, ByVal mypenradius As Integer)

    QCircle = New Rectangle(imgX - mypenradius, imgY - mypenradius, mypenradius * 2, mypenradius * 2)

    Dim g As Graphics = Me.CreateGraphics()

    DrawCircle(g, Color.Red, QCircle.X, QCircle.Y, QCircle.Width, QCircle.Height, 0, 360)

    g.Dispose()

    'Me.Refresh()

    Me.Invalidate()

  End Sub

End Class

Open in new window

doublecircle.png
0
Comment
Question by:tedunni
  • 3
4 Comments
 
LVL 85

Accepted Solution

by:
Mike Tomlinson earned 250 total points
ID: 24033304
Create a CURSOR instead of trying to draw that puppy all over the place...  ;)
Public Class Form1
 

    Private radius As Integer = 20

    Private startAngle As Integer = 0

    Private sweepAngle As Integer = 360

    Private currentColor As Color = Color.Red
 

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load

        CreateCursor()

    End Sub
 

    Private Sub CreateCursor()

        Dim bmp As New Bitmap(radius * 2, radius * 2)

        Dim g As Graphics = Graphics.FromImage(bmp)

        Dim myPen As New Pen(currentColor, 1)

        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.AntiAlias

        g.DrawArc(myPen, 0, 0, bmp.Width - 1, bmp.Height - 1, startAngle, sweepAngle)

        g.Dispose()

        myPen.Dispose()
 

        Dim C As New Cursor(bmp.GetHicon)

        Me.Cursor = C

    End Sub
 

End Class

Open in new window

0
 

Author Closing Comment

by:tedunni
ID: 31564963
Thanks, this solution is perfect.
0
 

Author Comment

by:tedunni
ID: 24051593
Idle_Mind, I'm going to ask a related question regarding this, but if I were to have a radius of say 48 it only draws part of the circle.  Additionally, if the radius gets quite large (try 576), then I get a GDI+ exception.  Any suggestions.  

Btw, the related question wizard keeps asking me to assign a title for the question (Even when I assign one), and so I'm posting here but once I get that figured out I'll post the link to the related question.
0
 

Author Comment

by:tedunni
ID: 24051610
0

Featured Post

DevOps Toolchain Recommendations

Read this Gartner Research Note and discover how your IT organization can automate and optimize DevOps processes using a toolchain architecture.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

In my previous two articles we discussed Binary Serialization (http://www.experts-exchange.com/A_4362.html) and XML Serialization (http://www.experts-exchange.com/A_4425.html). In this article we will try to know more about SOAP (Simple Object Acces…
Creating an analog clock UserControl seems fairly straight forward.  It is, after all, essentially just a circle with several lines in it!  Two common approaches for rendering an analog clock typically involve either manually calculating points with…
This is used to tweak the memory usage for your computer, it is used for servers more so than workstations but just be careful editing registry settings as it may cause irreversible results. I hold no responsibility for anything you do to the regist…
Internet Business Fax to Email Made Easy - With eFax Corporate (http://www.enterprise.efax.com), you'll receive a dedicated online fax number, which is used the same way as a typical analog fax number. You'll receive secure faxes in your email, fr…

910 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question

Need Help in Real-Time?

Connect with top rated Experts

21 Experts available now in Live!

Get 1:1 Help Now