Q: Persistent Graphics on Form or PicBox: a real pain!!!

Q: Persistent Graphics on Form or PicBox: a real pain!!!

• Samer Selo

  All right!! for the first time I am starting to see light at the end of the tunnel (has costed me many days).

  That discussion by John has actually yielded persistent graphics in selfdefined cartesian coordinate system!! Thanks.

  BUT to show the graphics with this approach is unbelievably slow, in my approach, because I have to draw millions of line pieces and after each one want to see an update. The update is by

  <Form>

  Dim myGraphics As Graphics

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

  Dim penred As New Pen(Color.Red, 0.1) 'this routine: code stolen from Johns example mixed with mine

  PicBox3.Image = New System.Drawing.Bitmap(PicBox3.ClientRectangle.Width, PicBox3.ClientRectangle.Height, Imaging.PixelFormat.Format32bppRgb)

  PicBox3.Image = New System.Drawing.Bitmap(PicBox3.ClientRectangle.Width, PicBox3.ClientRectangle.Height)

  myGraphics = Graphics.FromImage(PicBox3.Image)

  Dim mx3 As New Matrix((PicBox3.Width / 50), 0, 0, (-PicBox3.Height / (4 - -1)), 0, 0) 'THIS scales X 0 to 50, Y -1 to 4

  mx3.Translate(0, -4) 'Move 0,0 to mid left

  myGraphics.Transform = mx3

  End Sub

  'and THIS is what gets so slow:

  Private Sub BtnCalculation01_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles BtnCalculation01.Click

  Dim i As Integer

  Dim penorange As New Pen(Color.Orange, 0.001

  For i = 0 To 50000000

  myGraphics.DrawLine(penorange, 0, 0, i/1000000, sin(i/1000000)) 'just an example formula to show the idea. it actually

  'plots the results of a simulation

  PicBox3.Refresh() 'THIS step takes forever because it is executed 50 million times

  Next

  End Sub

  Anybody with any ideas to resolve this

  Thanks, Kesim.

  
  

• Ute

  see johns discussion in this thread:

  http://forums.microsoft.com/MSDN/ShowPost.aspx PostID=919200&SiteID=1

  
  
  

• Jessie Zhao

  Hi Kesim,

  Sorry for the late reply I've been out of action due to some knee surgery. Happily Dman1 posted a link to my other thread where I spent some time documenting the techniques you needed.

  Thank you for posting your code. I cut and pasted it into project and fired it up. I see what you mean about the slow speed draws. This is seems to be caused by the picturebox coping the bitmap from memory to its display surface. My guess would be that the larger the bitmap the slower the draws would become.

  There's a couple of things you can do to overcome this problem, but from your source code I don't see any need to make the solution too complex. If you're going to draw everthing in a loop, then the application will be unable to respond to external paint events (requests to repaint part or all of the application in Windows). With this in mind you can simply draw on the picture box itself as well as a bitmap in memory. Once the loop completes you can copy the bitmap from memory to the picturebox.image property. Using this technique will speed things up but it will also result in some ugly looking forms if a user starts messing with other applications that require a repaint of your application.

  Private Sub cmdNonPersist_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdNonPersist.Click

  '3)----The next lines are needed for NON-persistent graphics only

  'Create an off screen bitmap in memory
  Dim myOSB As New System.Drawing.Bitmap(PicBox1.ClientRectangle.Width, PicBox1.ClientRectangle.Height, Imaging.PixelFormat.Format32bppRgb)

  Dim myGraph As Graphics

  'Assign a graphics object to my bitmap in memory
  myGraph = Graphics.FromImage(myOSB)

  'clear my bitmap in memory setting its background color to the same color as my picture box
  myGraph.Clear(PicBox2.BackColor)

  grafiekNonPersist = PicBox2.CreateGraphics

  '------HERE THE GRAFIEK IS SET TO POINT TO picbox1.graphics, which is NON-persistent

  grafiekNonPersist.Transform = MT 'rescale the stuff
  myGraph.Transform = MT 'rescale the off screen image as well

  For i As Long = 1 To 10000
  grafiekNonPersist.DrawLine(penred, data(i - 1, 0), data(i - 1, 1), data(i, 0), data(i, 1)) 'THIS LINE and the next are all it takes

  'make a copy of the line on my off screen bitmap
  myGraph.DrawLine(penred, data(i - 1, 0), data(i - 1, 1), data(i, 0), data(i, 1))

  Next

  'copy the off screen bitmap to my picture box for persistance.
  PicBox2.Image = myOSB

  End Sub

  Johnny

  
  

• John Lieurance

  Interesting; but I think if you drop a picturebox on a form, doc it to form fill, create a bitmap and assign it to the picturebox.image property of the picture box upon the form load event you should get what you need. Realatively simple; however, very different from VB6.

  
  

• Ashish Saxena

  THIS is what I came up with in the end. It works OK but I am open to any suggestions to further improve it.

  Thanks for all who helped.

  Kesim

  Public Class Form1

  'KEES example persistent en non-persistent graphics in VB.net

  'Idea is this: in VB6, you could just draw on a picbox, and setting

  'autoredraw was sufficient to get persistent graphics.

  'In .Net, you have to do that differently.

  '****First, you can graph in a picbox by directly plotting to the graphics object

  'resulting in NON-PERSISTENT graphics.

  '****Second, you can plot to a BitMap that is within a PicBox, and that will yield

  'persistent plots. However, you need to call the refresh method to update the

  'screen after each plotted section.

  'NOTE that a reference to System.Drawing.Drawing2D must be set!!!

  'Form contains PicBox1 and PicBox2 (equal size) and 3 cmdButtons

  Dim grafiekPersist As Graphics 'accesible from all subroutines

  Dim grafiekNonPersist As Graphics 'accesible from all subroutines

  'now just define some things

  Dim penred As New Pen(Color.Red, 0.001)

  Dim Xmax As Single = 10000 'some scaling parameters to make Cartesian coordinates

  Dim Ymin As Single = -1.1 'between 0 < X < 10000 and -1.1 < Y < 1.3, par example

  Dim Ymax As Single = 1.3

  Dim MT As Matrix

  Dim data(10000, 1) As Single

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

  'prepare scaling matrix for Cartesian scale

  Dim transforMatrix As New Matrix((PicBox1.Width / Xmax), 0, 0, (-PicBox1.Height / (Ymax - Ymin)), 0, 0)

  transforMatrix.Translate(0, -Ymax) 'Move 0,0 to mid left

  MT = transforMatrix 'MT is globally accesible

  'now prepare some data

  For i As Single = 0 To 10000

  data(i, 0) = i

  data(i, 1) = Math.Sin(i / 100)

  Next

  End Sub

  'Example 1: persistent, SLOW. A MINIMAL version that refreshes after each line so it is very slow

  Private Sub cmdPersist_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdPersist.Click

  '1)----The next lines are needed for persistent graphics only

  '------create a bitmap in memory and display it in the picture box.

  PicBox1.Image = New System.Drawing.Bitmap(PicBox1.ClientRectangle.Width, PicBox1.ClientRectangle.Height, Imaging.PixelFormat.Format32bppRgb)

  PicBox1.Image = New System.Drawing.Bitmap(PicBox1.ClientRectangle.Width, PicBox1.ClientRectangle.Height)

  '------this latter statement is needed to make it white

  grafiekPersist = Graphics.FromImage(PicBox1.Image) 'HERE THE GRAFIEK IS SET TO POINT TO THE IMAGE, which is persistent

  grafiekPersist.Transform = MT 'rescale the stuff

  For i As Long = 1 To 10000

  grafiekPersist.DrawLine(penred, data(i - 1, 0), data(i - 1, 1), data(i, 0), data(i, 1)) 'THIS LINE and the next are all it takes

  PicBox1.Refresh()

  Next

  End Sub

  'Example 2: persistent, FAST

  Private Sub cmdPersistFast_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdPersistFast.Click

  '2)----The next lines are needed for persistent graphics only

  '------create a bitmap in memory and display it in the picture box.

  PicBox1.Image = New System.Drawing.Bitmap(PicBox1.ClientRectangle.Width, PicBox1.ClientRectangle.Height, Imaging.PixelFormat.Format32bppRgb)

  PicBox1.Image = New System.Drawing.Bitmap(PicBox1.ClientRectangle.Width, PicBox1.ClientRectangle.Height)

  '------this latter statement is needed to make it white

  grafiekPersist = Graphics.FromImage(PicBox1.Image) 'HERE THE GRAFIEK IS SET TO POINT TO THE IMAGE, which is persistent

  grafiekPersist.Transform = MT 'rescale the stuff

  For i As Long = 1 To 10000

  grafiekPersist.DrawLine(penred, data(i - 1, 0), data(i - 1, 1), data(i, 0), data(i, 1)) 'THIS LINE and the next are all it takes

  If i Mod 50 = 0 Then PicBox1.Refresh() 'take this line out for even faster response

  Next

  PicBox1.Refresh()

  End Sub

  'Example 3: NON-persistent, very fast

  Private Sub cmdNonPersist_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles cmdNonPersist.Click

  '3)----The next lines are needed for NON-persistent graphics only

  grafiekNonPersist = PicBox2.CreateGraphics

  '------HERE THE GRAFIEK IS SET TO POINT TO picbox1.graphics, which is NON-persistent

  grafiekNonPersist.Transform = MT 'rescale the stuff

  For i As Long = 1 To 10000

  grafiekNonPersist.DrawLine(penred, data(i - 1, 0), data(i - 1, 1), data(i, 0), data(i, 1)) 'THIS LINE and the next are all it takes

  Next

  End Sub

  End Class

  
  

• shitbhar

  John, could you elaborate a bit on that Or point me to an info source on that

  Thanks, Kesim

  
  

• joeycalisay

  OK. After hours and hours of further searching I found out that THIS IS SIMPLY NO LONGER POSSIBLE!!!

  It is a fundamental choice of vb.net to no longer support this type of things. Workarounds may be perceived by grabbing all graphics into a bitmap that has to be saved by the user, but this of course is not the real thing (because it does not allow later scaling etc).

  See the excellent paper on this by sp!ke in vbcity forum:

  http://vbcity.com/forums/topic.asp tid=128254

  again, too bad. Why doesn't MS simply offer us the choice

  kesim

  
  
• Q: Persistent Graphics on Form or PicBox: a real pain!!!