Rotating Rectangle

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Hello everyone...
I'm drawing a rectangle using the Rectangle Class, but I want to rotate this rectangle around its Pivot. It means it stays in its location, but is rotating - it will look like roolling.

How can I do it please?

Posted 6-Nov-10 4:32am

chernobel

Updated 4-Dec-17 19:03pm

JF2015

v2

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OriginalGriff 6-Nov-10 12:38pm

See revised answer.

3 solutions

Solution 1

See MSDN: Graphics.RotateTransform method[^]

Basically, to rotate a rectangle by 20 degrees clockwise in your paint event:

e.Graphics.RotateTransform(20.0F);
e.Graphics.DrawRectangle(Pens.Red, new Rectangle(5, 5, 30, 40));

"thnx ..it worked...but if i want to execute this in the Timer_tick event .for every second a rotation happened .. is that possible..and How please ?? Thanx anyway"

Firstly, don't draw in your timer event. Instead, handle the Paint event for a Panel or the Form, and draw there. Then in your timer event, change the angle to want top draw at (in a class level variable) and use the Invalidate method on the Panel or Form.

C#

private float rotateAngle = 0.0F;
private void timer1_Tick(object sender, EventArgs e)
    {
    rotateAngle += 5.0F;        // Step the draw angle on
    if (rotateAngle > 360.0F)
        {
        rotateAngle = 0.0F;
        }
    MyPanelForDrawingRectanglesOn.Invalidate();
    }

I would prefer to use a panel as the drawing won't then go beneath any other controls, but it is up to you...

Posted 6-Nov-10 5:29am

OriginalGriff

Updated 6-Nov-10 6:38am

v2

Comments

chernobel 6-Nov-10 12:23pm

thnx ..it worked...but if i want to execute this in the Timer_tick event .for every second a rotation happened .. is that possible..and How please ?? Thanx anyway

chernobel 6-Nov-10 13:22pm

it worked very good but with a problem that the rectangle is rotating around the top left corner..
i try the method RotatAt()...to rotate around the center of the rectangle.. but it didn't work...
so how can i solve it? please.

Solution 3

'simple.
'use this matrix
mat = New Drawing2D.Matrix
mat.RotateAt(angle, New Point(x+ rect.Width / 2, y+ rect.Height / 2))
'y and x are points of drawing rectangle
Dim gr As Graphics= Me.CreateGraphics
gr.Transform = mat
gr.DrawRectangle(pen.color, x, y, rect.Width,rect.Height)

Posted 10-Sep-15 15:13pm

Yusuf M Hamza

Comments

Dave Kreskowiak 10-Sep-15 23:29pm

Don't post answers to 5 year old questions. Your answer doesn't really add anything to the discussion at all.

Member 14959834 17-Feb-23 15:31pm

it helped me almost 8 years from his solution and 13 years after question...

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Heinzzy · Accepted Answer · 2010-11-06T09:12:00

Don't forget to make TranslateTransform if you want to rotate around other then (0,0) point.

C#

public partial class Form1 : Form
    {
        Timer timer;
        int angle;
        public Form1()
        {
            InitializeComponent();
        }
        private void Form1_Load(object sender, EventArgs e)
        {
            this.Paint += new PaintEventHandler(Form1_Paint);
            angle = 0;
            timer = new Timer();
            timer.Tick += new EventHandler(timer_Tick);
            timer.Interval = 10;
            timer.Start();
        }
        void Form1_Paint(object sender, PaintEventArgs e)
        {
            Graphics g = this.CreateGraphics();
            //the central point of the rotation
            g.TranslateTransform(100, 100);
            //rotation procedure
            g.RotateTransform(angle);
            g.DrawRectangle(Pens.Red, new Rectangle(0, 0, 50, 30));
        }
        void timer_Tick(object sender, EventArgs e)
        {
            angle++;
            this.Invalidate();
        }
    }

Rotating Rectangle

3 solutions

Solution 1

Solution 2

Solution 3

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