picturebox drawlines are remove in button click.

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dear friends,

i have this code for drawlines in picturebox and i want that all lines are remove in button click , and after user mouse click then these lines are not show.

thanks

C#

int iNumberofClicks = 0;
        Point[] pointArray = new Point[100];

 private void pictureBox1_MouseClick(object sender, MouseEventArgs e)
        {
            pointArray[iNumberofClicks].X = e.X;
            pointArray[iNumberofClicks].Y = e.Y;
            Pen PenSpikes = new Pen(Color.Green);
            SolidBrush solidBrush = new SolidBrush(Color.Blue);

            if(iNumberofClicks==0)
            {
                 a = e.X;
                 b = e.Y;
            }

            iNumberofClicks++;
            if (iNumberofClicks > 1)
            {
                Point[] CurrentpointArray = new Point[iNumberofClicks];

                for (int aa = 0; aa < iNumberofClicks; aa++)
                {
                    CurrentpointArray[aa].X = pointArray[aa].X;
                    CurrentpointArray[aa].Y = pointArray[aa].Y;

                }

                Graphics offScreenDC = Graphics.FromImage(pictureBox1.Image);
                offScreenDC.DrawLines(PenSpikes, CurrentpointArray);
                offScreenDC.Dispose();
                pictureBox1.Refresh();
                //
                for (int j = 1; j < CurrentpointArray.Length;j++ )
                {
                    //int d=(Convert.ToInt16(CurrentpointArray[j].X));
                    //int f=Convert.ToInt16(CurrentpointArray[j].Y);
                    if (Convert.ToInt16(CurrentpointArray[j].X) == a  && Convert.ToInt16(CurrentpointArray[j].Y) == b  )
                    {
                        MessageBox.Show("alert");
                            break;
                    }
                }
                Array.Clear(CurrentpointArray,0,CurrentpointArray.Length);
            }
        }

Posted 18-May-12 21:06pm

indreshkumar23

Updated 18-May-12 21:09pm

Wendelius

v2

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OriginalGriff · Answer 1 · 2012-05-18T21:24:00

The problem is that you are drawing directly on the image:

C#

Graphics offScreenDC = Graphics.FromImage(pictureBox1.Image);

Which means that the Image held in the PictureBox control is modified directly. The only way to "undo" those changes is to reload the image from the original source.

BTW: If you construct a Graphics object as above, then you are responsible for calling Dispose on it - if you don't, then your program will crash unpredictably, as Graphics contexts are scarce resource.

Personally, I would handle the PictureBox Paint event, and draw all the required lines there using the Graphics context supplied, rather than drawing on the Image directly (unless you intend to save the Image afterwards, and even then I would just apply the changes immediately before I wrote the file).