5. Projects using Intrinsic and Professional ActiveX Controls(4)

     In this lesson we will consider the construction of the following Graphic Projects:

·        1.  Drawing the graph for any function

·        2.  Drawing Pie Chart

·        3.  Colored Pixels

·        4.  Color Gradient

One can place Graphics on three controls:

1. Form
2. PictureBox
3. ImageBox

The main difference between these three controls is that the ImageBox is specially designed for displaying bitmaps, whereas the other two controls provide drawing methods, which let you design graphics at run time.

1. Project for Graphing any Function:

Drag a Picture box, and two command button  in the form, size them, caption them and position them as shown in the figure 1.     Open the code window of the command button and enter the codes as shown in the figure 1a.  Save and run the project.   You will get the graph for the function cos(3x)*sin(5x).   You can try with different types of functions and see how the scale properties are calculated for each function and the graphs are drawn.   A typical output is shown in the figure 2. 

                              Figure 1

Private Sub Command1_Click()

Dim t, functionval As Double

Dim xmin, xmax, ymin, ymax As Double

ymin = 1E+33: ymax = -1E+33

xmin = 2: xmax = 10

Picture1.Cls

Picture1.ScaleMode = 3

xpixels = Picture1.ScaleWidth - 1

'calculate min and max for y axis

For i = 1 To xpixels

t = xmin + (xmax - xmin) * i / xpixels

functionval = functioneval1(t)

If functionval > ymax Then ymax = functionval

If functionval < ymin Then ymin = functionval

Next

'set a user defined scale mode

Picture1.Scale (xmin, ymin)-(xmax, ymax)

'plot the function

For i = 0 To xpixels

t = xmin + (xmax - xmin) * i / xpixels

Picture1.Line -(t, functioneval1(t))

Next

End Sub

Function functioneval1(ByVal x As Double) As Double

functioneval1 = Cos(3 * x) * Sin(5 * x)

End Function

Private Sub Command2_Click()

End

End Sub 

    Figure 1a

                              Figure 2