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# How to change picturebox coordinate system?

Posted on 2011-09-23
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Last Modified: 2012-05-12
Hey everyone, so I have this graphing program that graphs regression lines. As of now it works well with small numbers, and the size of the picturebox scales with how large the points are. However when dealing with large numbers the graph lags out because it is way to large. I need to be able to scale the graphs coordinates so that it always shows the regression line no matter how big. Default origin is the top left corner (0,0). If i have plot points at like (297400, 10000, etc etc) I need to orgin to change for those numbers. Heres some pictures

This is the graph with small numbers:
screen3up.jpg

Large Numbers - lags out from the graph size being too large
screen4b.jpg

The large numbers being plotted are {69400, 2500, 109000, 5000, 207900, 7500, 297200, 10000, 346500, 12500}

I know those numbers are valid because oither graphing prgrams plot them perfectly, because the coordinate system scales.

Heres my code, if you could give me some tips you would make me very happy, as well as my boss!!

``````Public Class Form1

'Declare variables
'-----------------------------------------------------
Private Structure PointType
Dim X As Double
Dim Y As Double
End Structure

Dim Reg As New RegressionObject
Private LastEndPoint As New Point(0, 0)

'Graph lines and points
Dim regLine As New Series
Dim points As New Series

'The radius
Const R = 100

'Point
Dim P(0 To 200) As PointType

'Array that holds X and Y values for graphing
Dim MyData() As Single = New Single() {69400, 2500, 109000, 5000, 207900, 7500, 297200, 10000, 346500, 12500}

'Scale graph to stay within the picturebox
Dim HorizontalScaleFactor As Single

'The array for the points on the graph
Dim DataPoints(MyData.Length - 1) As PointF

'Points where the number labels are drawn
Dim labels As PointF

'The font
Dim drawFont As New Font("Arial", 16)
Dim cordFont As New Font("Arial", 8)

'Regression degrees
Dim deg As Integer

Dim flag As Boolean
Dim loaded As Boolean

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

For i As Integer = 1 To 10
degBox.Items.Add(i)
Next
loaded = False
flag = False
degBox.Text = "3"
Reg.Degree = deg
End Sub

'This updates the picturebox everytime it is redrawn
Private Sub picboxPulseCurve_Paint(ByVal sender As Object, ByVal e As System.Windows.Forms.PaintEventArgs) Handles picboxPulseCurve.Paint

Dim i As Integer

e.Graphics.SmoothingMode = Drawing2D.SmoothingMode.HighQuality
'e.Graphics.DrawCure(ve(Pens.Blue, DataPoints))
regLine.Name = "Regression Curve"
regLine.ChartType = SeriesChartType.Spline
regLine.Color = Color.Maroon
With Reg
Using pn As New Pen(Color.Red, 2)
For i = 0 To .XYCount
DrawACircle(e, pn, New Point(P(i).X, P(i).Y), R / 10)
Next i
End Using

LastEndPoint = New Point(0, .RegVal(CDbl(Me.ClientRectangle.Height)))
Dim CurrentPoint As Point
For i = 0 To Me.ClientRectangle.Width Step R
CurrentPoint = New Point(i, .RegVal(CDbl(i)))
Using pn As New Pen(Color.BlueViolet, 3)
e.Graphics.DrawLine(pn, LastEndPoint, CurrentPoint)
End Using
e.Graphics.DrawLine(Pens.Red, 0, MyData.Max + 150, 0, 0)
e.Graphics.DrawLine(Pens.Red, MyData.Max + 150, 0, 0, 0)
If (flag = False) Then
regLine.Points.AddXY(-CurrentPoint.X, -CurrentPoint.Y)
End If
LastEndPoint = CurrentPoint
Next i
If (flag = False) Then
graph.Series.Add(regLine)
graph.Series.Add(points)
End If
End With
End Sub

'Draws a circle at the given points
Private Sub DrawACircle(ByVal e As System.Windows.Forms.PaintEventArgs, ByVal P As Pen, ByVal center As Point, ByVal radius As Integer)
' Create a bounding rectangle and make its center the center of our point
' Then make its width 2 * the radius
' Then draw our ellipse
points.Name = "Points"
points.ChartType = SeriesChartType.Point
points.Color = Color.Black
Dim rect As New Rectangle(center, New Size(0, 0))

For i = -3000 To MyData.Max + 150 Step 50
labels = New Point(i, 0)
e.Graphics.DrawString(i.ToString(), drawFont, Brushes.Black, labels)
e.Graphics.DrawLine(Pens.Black, i, 0, i, MyData.Max + 150)
Next

For i = -3000 To MyData.Max + 150 Step 50
labels = New Point(0, i)
e.Graphics.DrawString(i.ToString(), drawFont, Brushes.Black, labels)
e.Graphics.DrawLine(Pens.Black, 0, i, MyData.Max + 150, i)
Next

rect.Inflate(radius, radius)
e.Graphics.DrawEllipse(P, rect)
e.Graphics.DrawString(center.X.ToString() + " " + center.Y.ToString(), cordFont, Brushes.Black, New PointF(center.X + 8, center.Y))
If (flag = False) Then
points.Points.AddXY(-center.X, -center.Y)
End If
End Sub

'This button resets the graphs and data
Private Sub resetBtn_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles resetBtn.Click
flag = False
regLine.Points.Clear()
points.Points.Clear()
graph.Series.Clear()
txtBox.ResetText()
Reg.Init()

MsgBox("Data has been reset!")
End Sub

'This populates the program with graph points that are loaded from a file
'It also resets the graphs and data
Private Sub PopulateDataPointsArray(ByVal PictureBoxWidth As Integer)
'Scale the graph to fit the picture box:
HorizontalScaleFactor = CSng(PictureBoxWidth / DataPoints.Length)
picboxPulseCurve.Width = MyData.Max + 150
picboxPulseCurve.Height = MyData.Max + 150

If (flag = False) Then

regLine.Points.Clear()
points.Points.Clear()
graph.Series.Clear()
End If
txtBox.ResetText()
Reg.Init()

'Populate the DataPoints array:
For i As Integer = 0 To DataPoints.Length - 2
DataPoints(i).X = MyData(i)
DataPoints(i).Y = MyData(i + 1)

txtBox.Text += ("X: " + MyData(i).ToString() + " Y: " + MyData(i + 1).ToString() + vbNewLine)

With Reg
.XYAdd(DataPoints(i).X, DataPoints(i).Y)
P(.XYCount).X = DataPoints(i).X
P(.XYCount).Y = DataPoints(i).Y
End With

Next

Me.Refresh()

End Sub
``````
0
Question by:ezdrt
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17 Comments

LVL 13

Expert Comment

ID: 36588658
You are going to need a new approach.

You will have to use some easy math to scale the graph before you draw it, and keep the size of the PictureBox constant.

Scaling the ever growing picturebox is a hugely inefficient use of RAM, and as you found out, it doesn't work with large sets.
0

Author Comment

ID: 36588674
Yeah I didnt realize that until after I made the picture box size scale the way it does. Ive been searching for a way to just change the picturebox orgin. Was way easier in VB6 :(
0

LVL 13

Expert Comment

ID: 36588680
I may have jumped the gun on my answer, it seems you are already doing this to an extent. Let me actually comb through this now and I will try and give you a better response
0

LVL 13

Expert Comment

ID: 36588684
Yes I remember vb6, was my personal favorite... .NET cluttered everything up!
0

Author Comment

ID: 36588690
Thanks Id appreciate it:) Im the only programmer working on this project so a new set of eyes would help a lot.
0

LVL 13

Expert Comment

ID: 36588719
Btw, my initial response was correct ;), I was just working too quickly, I saw your scale factor and my brain assumed you were applying it differently, .... anyway.

Lets see, if you keep the picturebox costant at 1000x1000 for example, the math should be:

plotx = 64000

plotwidth = 75000

actualwidth = 1000

scalefactor = actualwidth / 75000

drawx = plotx * scalefactor

do the same for y, and this will give you multipliers that you apply to the variables before you draw them. this way, as far as vb is concerned, you are drawing withing the box, all the math happens BEFORE translation.

oh ya, and as far as the tick marks, you simply draw whatever number you want on the graph, and have it match the MATH numbers, not the pixel numbers.

(question, does it always start at 0,0?, if not, you will need to find the distance away from 0, multiplied by the scale factor, and then REMOVE this amount from the actual graphing of the reg line)

Lot of information here, let me know what you come back with :)
0

LVL 13

Accepted Solution

themrrobert earned 334 total points
ID: 36588768
Sorry, I don't think I'll be able to write you a working code snippet, I no longer have vb installed.

However, I can help get you there. For starters, you will want to have (in your Window.onResize event)

Ok, at the top, and a new Private variable PB_WIDTH and PB_HEIGHT, this amount will be updated in the routine i'm about to describe:
a route which shrinks or grows the picturebox to match the amount of room left. This should be relatively easy, you can find the new width by taking Form.width - PictureBox.Left (and the same for Top/Height)

Since this is your code, you are best prepared to modify it. With your recently populated PB_WIDTH and PB_HEIGHT variables, you can get the scale as follows (i'm not sure how you want to define the max, perhaps the highest value rounded up to nearest 10,000, you can fill in that yourself)

so you have SCALEY = PB_HEIGHT / SCALEYMAX and SCALEX = PB_WIDTH / SCALEXMAX
(the numbers i just had you find)

this gives you the multiplier you will apply to all numbers to be plotted BEFORE drawing.

hack out all of the code that scales the picturebox, and instead, keep the PB constant, and add in new code in form of (SCALEX * VARTOBEDRAWN) or similar.

Hopefully this gets you where you need. I will check back later to see if you need anymore help :)
0

Author Comment

ID: 36588791
ahh ok I see where youre going there, let me try some stuff out and ill get back to you:)

Oh and that scale factor I had in there, wasnt working at all. It would only work if you were plotting only y coordinates for some reason
0

LVL 13

Expert Comment

ID: 36588970
Yea ;) well i think you were on the right track with that, it just got lost among the easier automatic pb scaling :D

I'm sure you're well on your way to a much more powerful and robust graphing program, with a much smaller memory footprint.

I'll be back
0

LVL 86

Expert Comment

ID: 36589027
In DrawACircle(), lines #108 thru #118, why are you redrawing the labels for every circle?  Those should be drawn ONCE.  Move those lines to line #71.5 (yes...71 and a Half).  DrawACircle() should, well, just "draw a circle".  Making it also draw the labels violates the "make every sub/function do ONE thing and do it WELL" rule.  ;)

At lines #81 thru #83, you're creating a new pen instance for every single line drawn!  The Pen color/width isn't being changed for any particular line so you should create ONE Pen outside the loop and re-use it the entire time.  Move line #81 to #78.5 and line#83 to #90.5.

Make those changes first and see if the performance increases.

0

Author Comment

ID: 36589361
Yeah that did help performance a little bit, thanks Idle ;)! Sometimes I overlook stuff like that would ive been staring at this screen for 8 hours haha.

Still working on that scaling using the tips themrrobert gave me. No luck yet :(
0

LVL 86

Assisted Solution

Mike Tomlinson earned 166 total points
ID: 36589679
Another approach is to do the scaling math as proposed by themrrobert but then use the Graphics.ScaleTransform() method and plot still using the raw data:
http://msdn.microsoft.com/en-us/library/zhc2xxtx.aspx

*Leave the scaling at 1:1 to draw the grid and labels first, then scale afterwards to draw the rest of the graph.
0

Author Comment

ID: 36590464
hmmm

so scale transform seems to be working on the line :)

Now i just gotta use themrroberts logic on the pictureBox to scale that accordingly...same with the circles, they need to appear in the right spots.
0

LVL 86

Expert Comment

ID: 36590510
If they are in the same scale, then the line and circles should all be in the correct spots.  You may need to draw them bigger, though, so they are visible to the user.
0

Author Comment

ID: 36590533
Yep I just moved the line of code up a little further, now everything scales correctly. Multiplied them by a large number so you can actuall see them now.

screen5rx.jpg

0

LVL 13

Assisted Solution

themrrobert earned 334 total points
ID: 36590692
excellent! You are nearly there.

It seems you still need to adjust the the labels on the X and Y axis to match the scale, but other than that it looks good. is there anything else that you need?
0

Author Closing Comment

ID: 36590709
Nope I think I got it from here, thank both of you for your help:) A+!
0

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