Create Custom Component in C# - Draw a Compass

Create Custom Component in C# - Draw a Compass

Hello everyone, in this article we are going to create a custom component with C# in Visual Studio. We are going to create an Aircraft Compass Component and we use it in our winform application.

Let's begin.

Before we starting, I strongly recommend to take a look at below article if you have no idea how to create a Custom Component with C# in Visual Studio. I talked about it before.
How to create custom components in CSharp (C#)

Firstly we need to create a new project and add a new component element in the project.

  • First step : Right Click on Project Add New Folder Name as you want
  • Second Step : Right Click on created Folder Add New Item Select Custom Control Name as you want and add it.

Below image you can see my component folder and my custom control. Create a Custom Control in Related Folder

Do not forget to Rebuild the project. Otherwise you can not see this component on the Toolbox. This is essential.

And now we are ready to drag-drop the component on the form and write some code to create our custom compass.

Before I started to write for compass drawing method, I want to talk about a method which I used. Normally all characters will be texted at the center of the compass, so I need to spread them to the related location. According to this requirement I will create a hidden circle and I will text these characters on this circle. I will decide the readius of this circle with below function.

This function return the needed distance from center of the compass for the required markings of the compass

public static double charSpread(double swidth)
     return swidth / 6;

Now let's write the compass drawing method in CustomCompass class related method.

Declare a method name Draw compass with degree parameter which returns a Bitmap:

public Bitmap DrawCompass(double degree)

Firstly we are going to create our configuration variables:

First we need to know the component size.
Then we create an image object and then a graphic object from this image. We needgraphic object to make some drawings which in need for a compass
Set a black background for the compass

Size s = this.Size;

Bitmap compassImage = new Bitmap(s.Width, s.Height);
Graphics g = Graphics.FromImage(compassImage);

SolidBrush blackBrush = new SolidBrush(Color.Black);
Rectangle rect = new Rectangle(0, 0, compassImage.Width, compassImage.Height);
g.FillRectangle(blackBrush, rect);

In here first we are going to declare some essential variables.
  • maxRadius variable will hold the max radius of compass. It will make the compass fit to the window.
  • sizeRatio variable will make the textx and lines appropraite according to window dimensions
  • outerradius and innerradius will specify the compass lines locations. Starting and ending points of the compass lines
  • markingsRadius will hold the radius of hidden circle of which hold the markings location

double maxRadius = s.Width > s.Height ? s.Height / 2 : s.Width / 2;
double sizeRatio = maxRadius / 360;
double outerradius = maxRadius - sizeRatio * 60;
double innerradius = maxRadius - sizeRatio * 90;
double markingsRadius = maxRadius - sizeRatio * 135; 

Here we need to configuration of the marking texts and lines styles. We will hold their sizes and colors here

Font font1 = new Font("Arial", (float)(25 * sizeRatio));
SolidBrush brushWhite = new SolidBrush(Color.FromArgb(255, 255, 255));
Pen penThick = new Pen(Color.FromArgb(255, 255, 255), ((int)(sizeRatio) < 5 ? 5 : (int)(sizeRatio)));
Pen penThin = new Pen(Color.FromArgb(255, 255, 255), ((int)(sizeRatio) < 2 ? 2 : (int)(sizeRatio)));

We are going to draw everything according to center point. So I need to hold the center points of the compass.

int xCenter = (int)(s.Width / 2);
int yCenter = (int)((s.Height / 2));

We will also need the cosinus and sinus values of angles to locate the point even if the image has been rotated by a degree.

IMPORTANT : We are subtracting 90 from the angle because we need to rotate the image by 90 to counter clockwise because the axis started from 90 degrees and right side faced.

double[] Cos = new double[360];
double[] Sin = new double[360];
for (int a = 0; a < 360; a++)
        double curAngle = ((a - 90d) - degree) / 180F * Math.PI;
        Cos[a] = Math.Cos(curAngle);
        Sin[a] = Math.Sin(curAngle);

Until here our configurations are ready and After here we are going to create a For loop for every angle which I want to draw a line for my compass.

In this for loop we are going to decide how many lines we are gonna draw. As you can see below I increased the iterator by 5. So I will draw 360/5=72 lines.

All codes after this section will be inside of below FOR LOOP


            for (int d = 0; d < 360; d += 5)

Here is the logic of the program:

  • I will draw the thick lines at every 10 and its multiplies
  • I will draw the thin lines at every 5 and its multiplies
  • I will write the angles at every 30 degree
  • And I will write the main directions N at 0, E at 90, S at 180 and W at 270 degrees.

In here we are going to specify the compass lines starting and ending points. When we rotate the compassit will divide the circle into 360 parts and it will get the starting and ending points with a hidden triangle from the center. So I will use the cos and sin calculations to locate the point on the x and y axis.

Point pOuter = new Point((int)(outerradius * Cos[d]) + xCenter, (int)(outerradius * Sin[d]) + yCenter);
Point pInner = new Point((int)(innerradius * Cos[d]) + xCenter, (int)(innerradius * Sin[d]) + yCenter);

//Here I will locate the text as the same logic above. 
Point pMarkings = new Point((int)(markingsRadius * Cos[d]) + xCenter, (int)(markingsRadius * Sin[d]) + yCenter);
//Additionally I will center the text otherwise it will not located at the next of the compass line
SizeF s1 = g.MeasureString(d.ToString(), font1);
pMarkings.X = pMarkings.X - (int)(s1.Width / 2);
pMarkings.Y = pMarkings.Y - (int)(s1.Height / 2);

I will draw the thick lines first. Also I will perform the tasks which have to be performed at 30 and 90 degrees in here I will draw the lines and text the markings in here

                if (d % 10 == 0) 
                    //It will draw the line whatever happens at every multiplied by 10
                    g.DrawLine(penThick, pOuter, pInner);

                    //At Every 30 degress it will text the marking numbers.
                    if (d % 30 == 0)
                        //And every 90 degrees it will check and text main directions if it is
                        if (d % 90 == 0)
                            switch (d)
                                case 0:
                                case 360:
                                    g.DrawString("N", font1, brushWhite, pMarkings);
                                case 90:
                                    g.DrawString("E", font1, brushWhite, pMarkings);
                                case 180:
                                    g.DrawString(" S", font1, brushWhite, pMarkings);
                                case 270:
                                    g.DrawString("W", font1, brushWhite, pMarkings);
                        else //if current degree is not a main direction, it will write the degree
                            g.DrawString(d.ToString(), font1, brushWhite, pMarkings);

It will draw the compass lines at every remain 5 degrees.

else if (d % 5 == 0)
      g.DrawLine(penThin, pOuter, pInner);

For loop ended here

When we have done our tasks in for loops we need to return the image.

//Return the built compass image.
return compassImage;

At our component class we are going to declare a heading variable and an override method as OnPaintBackground. We will have an Update method which will take the command the Heading value from the other classes. UpdateCompass method will take the Heading value and update it in this component. And then it will update the compass.

private int Heading = 0;

 protected override void OnPaintBackground(PaintEventArgs pevent)
      //And lastly we are calling the Bitmap method on Painting Background override method to show it.
       pevent.Graphics.DrawImage(this.DrawCompass(this.Heading), new Point(0, 0));

//This function is required to refresh this component
public void UpdateCompass(int _heading)
      this.Heading = _heading;

I have created a form and I located a trackbar and my customcompass component. At trackbar value changed event I updated the compass values. Also I updated the compass at form resize event. Because I used anchor and I need to update the compass when form and component size changed.

private void trackBar1_ValueChanged(object sender, EventArgs e)

private void Form1_Resize(object sender, EventArgs e)

Below image you can see my form window. Custom Compass Component Example Output

That is all in this article.

You can find the example application on Github :

Have greate finding the directions with great compasses.

Burak Hamdi TUFAN


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  • Thecodeprogram User

    Nice example, especially sometimes I confused on using imaging libraries in C#, this example is long but really good :)

    2020/06/29 20:25:37