How to Use SetPixel Method to Draw a Function in VB.NET

This article shows how to use the SetPixel method to draw some mathematical functions. I created the MathGraph project under VB.NET (2003) to draw the following functions:



1- f(X) = x^2
2- f(X) = X^3
3- f(X) = sin(X)
4- f(X) = cos(X)
5- f(X) = |X^2- 4|
6- f(X) = |sin(X)|

The MathGraph project has one form (frmGraph) with the following controls:

• ListBox control (lstFunction) to select a function.
• Label control (lblFunctionName) to display function definition.
• PictureBox control (PicView) to display the function graph, this control has a background image from the file (..\..\images\Axis.jpg).
• Button control (btnDraw) to draw the function graph.
• Button control (btnExit) to close the program.

The Code

' Variables of my program
Dim PointArray As ArrayList = New ArrayList   ' series of points
Dim PageWidth As Integer ' Width of "ImageToDraw" Object
Dim PageHeight As Integer  ' Height of "ImageToDraw" Object
Dim xCenter As Integer  ' x coordinate of center
Dim yCenter As Integer  ' x coordinate of center
Dim ImageToDraw As Bitmap
Dim Pi As Double = Math.PI ' 22/7

//Set the Center coordinates and load ListBox with Functions:
Private Sub frmGraph_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles MyBase.Load
        ' Width of "PicView" control
        PicView.Width = 500 'don't change (it is for background image
        ' Height of "PicView" control
        PicView.Height = 380 'don't change (it is for background image

        ' Width of "ImageToDraw" Object as Width of  "PicView" control
        PageWidth = PicView.Width
        xCenter = Int(PageWidth / 2)
        ' Height of "ImageToDraw" Object as Height of  "PicView" control
        PageHeight = PicView.Height
        yCenter = Int(PageHeight / 2)

        ' Fill ListBox
        lstFunction.Items.Add("Function 1")
        lstFunction.Items.Add("Function 2")
        lstFunction.Items.Add("Function 3")
        lstFunction.Items.Add("Function 4")
        lstFunction.Items.Add("Function 5")
        lstFunction.Items.Add("Function 6")
        lstFunction.SelectedIndex = 0
End Sub

// Draw the function: f(X) = |Sine(X)|
Private Sub Function6()
        Dim W As Double = PageWidth / 20
        Dim H As Double = PageHeight / 4
        ImageToDraw = New Bitmap(PageWidth, PageHeight)
        ' Draw the function f(X) = |Sine(X)|.
        For X As Double = -2 * Pi To 2 * Pi Step 0.01
            Dim Z As Double = Math.Sin(X)
            Dim Y As Double = Math.Abs(Z)
            Dim PX As Double = xCenter + W * X
            Dim PY As Double = yCenter - H * Y
            ImageToDraw.SetPixel(Int(PX), Int(PY), Color.Blue)
        Next
        PicView.Image = ImageToDraw
        ImageToDraw = Nothing
    End Sub

Summary

In this article we have learned how to use the SetPixel method to draw curves. You can go to the source code file to read the code for drawing the other functions. If you have any idea about this code, please tell me. Thanks for C# Corner team and thanks for all.