|
|
Pie Chart in eVB
By Kosuri RajaSekhar, September 26, 2002.
Print version
Summary
This article helps you to display your data as a pie chart in eVB program.
It gives a sample code that you can use and modify.
Introduction
Pictures speak better than words. This article helps you to
display your data as a pie chart in eVB. We all know that
programming in eVb is easier but drawing graphical charts like
pie is not that easy as we dont have any predefined functions in
Embedded VB to draw pie charts. The application has a form consisting of
three controls PictureBox, textBox and a command Button. When You
click on the command button, the pie chart and a legend is displayed in
the Picture Box. when you click on one of the legendry boxes, details
of that particular sector are displayed in the textbox.
What You Need
Preface
Before answering your question "How can I use this Pie Chart in my application?",
let me first tell you what are the API calls and functions that have been used
in this application. To your surprise, drawline and drawcircle are the only
functions used in drawing the pie chart. Calculating the sectors and painting
them is complicated and tricky. For those who aren't interested in the intricacies can
directly add the form to their application and with minor changes done can represent
their data as a pie chart.
In Command1_Click(), Initialize the variable max_values and the array
input_values with the total number of values and actual values used in
drawing the pie chart.
Here it is:
<![CDATA[
Private Sub Command1_Click()
Command1.Enabled = False
Dim input_values() As Integer
Dim max_values As Integer
max_values = 4
ReDim input_values(max_values)
input_values(0) = 10
input_values(1) = 30
input_values(2) = 75
input_values(3) = 60
Draw_Pie (input_values)
End Sub
]]>
Private Sub Draw_Pie(). This method does three important things
- Calculates the points on the circle which are used to draw the sectors.
- Starts painting each sector with different colors.
- Also draws legendry boxes, later when clicked on each of these boxes, the details of the respective sector are displayed.
<![CDATA[
Private Sub Draw_Pie(values() As Integer)
Const c_x = 1200 'axis co-ordinates
Const c_y = 1200 'axis co-ordinates
Const radius = 1200 'radius
Dim angle() As Integer
Dim pts() As Integer
Dim i As Integer
Dim total As Integer
Dim cum_angle As Integer
Dim x_off As Integer
Dim y_off As Integer
ReDim angle(UBound(values))
ReDim Info(UBound(values))
ReDim colour_matrix(UBound(values), 5)
ReDim Info(UBound(values))
ReDim pts(UBound(values) + 1, 2)
pb.DrawWidth = 1
total = 0
For i = 0 To UBound(values) - 1
total = total + values(i)
Next
For i = 0 To UBound(values) - 1
angle(i) = values(i) / total * 360
Info(i) = Round((values(i) / total) * 100, 2) & "%"
Next
cum_angle = 0
pts(0, 0) = c_x
pts(0, 1) = c_y - radius
For i = 0 To UBound(angle) - 2
cum_angle = cum_angle + angle(i)
x_off = 0
y_off = 0
If cum_angle < 90 Then
If (cum_angle Mod 90) < 45 Then
y_off = radius
x_off = calculate_offset(cum_angle Mod 90, radius)
Else
x_off = radius
y_off = calculate_offset(90 - cum_angle Mod 90, radius)
End If
pts(i + 1, 0) = c_x + x_off
pts(i + 1, 1) = c_y - y_off
End If
If cum_angle >= 90 And cum_angle < 180 Then
If cum_angle Mod 90 < 45 Then
x_off = radius
y_off = calculate_offset(cum_angle Mod 90, radius)
Else
y_off = radius
x_off = calculate_offset(90 - cum_angle Mod 90, radius)
End If
pts(i + 1, 0) = c_x + x_off
pts(i + 1, 1) = c_y + y_off
End If
If cum_angle >= 180 And cum_angle < 270 Then
If cum_angle Mod 90 < 45 Then
y_off = radius
x_off = calculate_offset(cum_angle Mod 90, radius)
Else
x_off = radius
y_off = calculate_offset(90 - cum_angle Mod 90, radius)
End If
pts(i + 1, 0) = c_x - x_off
pts(i + 1, 1) = c_y + y_off
End If
If cum_angle >= 270 And cum_angle < 360 Then
If cum_angle Mod 90 < 45 Then
x_off = radius
y_off = calculate_offset(cum_angle Mod 90, radius)
Else
y_off = radius
x_off = calculate_offset(90 - cum_angle Mod 90, radius)
End If
pts(i + 1, 0) = c_x - x_off
pts(i + 1, 1) = c_y - y_off
End If
Next
pts(UBound(angle), 0) = c_x
pts(UBound(angle), 1) = c_y - radius
'/////////////////////////////
'Fill colour logic
'/////////////////////////////
Dim x As Integer
Dim y As Integer
Dim r As Integer
Dim g As Integer
Dim b As Integer
Dim x_box As Integer
Dim y_box As Integer
Dim tot_height_boxes
If (UBound(pts) > 10) Then
tot_height_boxes = 10 * 200
Else
tot_height_boxes = UBound(pts) * 200
End If
x_box = c_x + radius
y_box = pb.Top + CInt((pb.Height - tot_height_boxes) / 2)
r = 20
g = 58
b = 150
i = 1
colour_matrix(0, 0) = r
colour_matrix(0, 1) = g
colour_matrix(0, 2) = b
y = c_y - radius
x = c_x
While x < c_x + radius
If x > pts(i, 0) And y = pts(i, 1) And pts(i, 0) > pts(i - 1, 0) Then
r = (b + 345) Mod 255
g = (r + 535) Mod 255
b = (g + 615) Mod 255
If (i < UBound(angle)) Then
colour_matrix(i, 0) = r
colour_matrix(i, 1) = g
colour_matrix(i, 2) = b
End If
i = i + 1
End If
pb.DrawLine c_x, c_y, x, y, RGB(r, g, b)
x = x + 15
Wend
x = c_x + radius
y = c_y - radius
While y < c_y + radius
If y > pts(i, 1) And x = pts(i, 0) Then
r = (b + 345) Mod 255
g = (r + 535) Mod 255
b = (g + 615) Mod 255
If (i < UBound(angle)) Then
colour_matrix(i, 0) = r
colour_matrix(i, 1) = g
colour_matrix(i, 2) = b
End If
i = i + 1
End If
pb.DrawLine c_x, c_y, x, y, RGB(r, g, b)
y = y + 15
Wend
y = c_y + radius
x = c_x + radius
While x > c_x - radius
If x < pts(i, 0) And y = pts(i, 1) Then
r = (b + 345) Mod 255
g = (r + 535) Mod 255
b = (g + 615) Mod 255
If (i < UBound(angle)) Then
colour_matrix(i, 0) = r
colour_matrix(i, 1) = g
colour_matrix(i, 2) = b
End If
i = i + 1
End If
pb.DrawLine c_x, c_y, x, y, RGB(r, g, b)
x = x - 15
Wend
x = c_x - radius
y = c_y + radius
While y > c_y - radius
If y < pts(i, 1) And x = pts(i, 0) Then
r = (b + 345) Mod 255
g = (r + 535) Mod 255
b = (g + 615) Mod 255
If (i < UBound(angle)) Then
colour_matrix(i, 0) = r
colour_matrix(i, 1) = g
colour_matrix(i, 2) = b
End If
i = i + 1
End If
pb.DrawLine c_x, c_y, x, y, RGB(r, g, b)
y = y - 15
Wend
y = c_y - radius
x = c_x - radius
While x < c_x
If x > pts(i, 0) And y = pts(i, 1) And pts(i, 0) > pts(i - 1, 0) Then
r = (b + 345) Mod 255
g = (r + 535) Mod 255
b = (g + 615) Mod 255
If (i < UBound(angle)) Then
colour_matrix(i, 0) = r
colour_matrix(i, 1) = g
colour_matrix(i, 2) = b
End If
i = i + 1
End If
pb.DrawLine c_x, c_y, x, y, RGB(r, g, b)
x = x + 15
Wend
pb.DrawLine c_x, c_y, c_x, y, RGB(r, g, b)
pb.DrawWidth = 50
pb.DrawCircle c_x, c_y, radius + 150, RGB(255, 255, 255), 1
'pb.DrawWidth = 1
'pb.DrawCircle c_x, c_y, radius - 215, RGB(0, 0, 0), 1
'/////////////////////////////
' Draw Legend Boxes
'/////////////////////////////
y = y_box
pb.DrawWidth = 10
For i = 0 To UBound(colour_matrix) - 1
If (i Mod 10) = 0 Then
x_box = x_box + 200
y_box = y
End If
colour_matrix(i, 3) = x_box
colour_matrix(i, 4) = y_box
pb.DrawPoint x_box, y_box, RGB(colour_matrix(i, 0), colour_matrix(i, 1), colour_matrix(i, 2))
y_box = y_box + 200
Next
End Sub
]]>
The On_Click event on the legendry boxes is handled in the
Sub pb_MouseDown(). When you click on any one of the legendry box,
the data related to that sector is read from an array "info" and
displayed in the "Text1" textbox. If you want to customize the data
related to each sector you can append the details in this function
as shown below.
<![CDATA[
Private Sub pb_MouseDown(ByVal Button As Long, ByVal Shift As Long, ByVal x As Double, ByVal y As Double)
Dim i As Integer
For i = 0 To UBound(colour_matrix) - 1
If x > colour_matrix(i, 3) - 75 And x < colour_matrix(i, 3) + 75
And y > colour_matrix(i, 4) - 75 And y < colour_matrix(i, 4) + 75 Then
Text1.Text = Info(i)
Exit For
End If
Next
End Sub
]]>
I hope this article will be helpful to all those programmers who are
searching for free tools to draw pie charts in eVB. If anyone is
interested in understanding the logic behind, they can always contact
me at Kosuri RajaSekhar.
Source code
You can download source code mentioned in this article - Source code (696 Kb).
Related resources:
Discuss
Discuss this article.
Here you can write your comments and read comments of other developers.
|
