I have a situation in which I want to make multiple bounding boxes on a picture and want to make them editable and moveable in my winform application.

Following is my effort

    public Graphics g;
    public Pen pen;
    public bool isMoving=false;
    public int X, Y;
    public int startX, startY;

    public Rectangle mRect;

    private void pBoxCenter_MouseDown(object sender, MouseEventArgs e)
    {
        isMoving = true;

       // X = e.X; 
        //Y = e.Y;

        startX= e.X; 
        startY = e.Y;

        pBoxCenter.Cursor = Cursors.Cross;
    }

    private void pBoxCenter_MouseMove(object sender, MouseEventArgs e)
    {
        if(isMoving && X!=-1 && Y!=-1)
        {



            g = pBoxCenter.CreateGraphics();
            pen = new Pen(Color.White, 2);
            Rectangle rectangle=getRectangle(e.X, e.Y);
            g.DrawRectangle(pen, rectangle);
            X =e.X; 
            Y=e.Y;
           
        }

    }

    private void pBoxCenter_MouseUp(object sender, MouseEventArgs e)
    {
        isMoving= false;

        X = -1;
        Y = -1;

    }
    

    private Rectangle getRectangle(int tempX,int tempY)
    {
        int X = Math.Min(startX,tempX);
        int Y = Math.Min(startY,tempY);

        int Width = Math.Abs(startX- tempX);
        int Height = Math.Abs(startY- tempY);

        mRect= new Rectangle(X,Y,Width,Height);

        return mRect;

    }

Results

I am not being able to draw a single bounding box because each time I draw , multiple bounding boxes get drawn on the location.Secondly,I am not being able to draw multiple bounding boxes on different locations as code get executed once. Finally, How can I make those bounding boxes editable beacuse I might have a situation to resize those bounding boxes , moving those bounding boxes or completely deleting them .

Regards

CodePudding user response：

First it's a pity that your approach to draw the picture box is wrong, don't call CreateGraphics, but register its Paint event.

private void pBoxCenter_Paint(object sender, PaintEventArgs e)
{
    Rectangle rectangle = getRectangle(X, Y);
    e.Graphics.DrawRectangle(pen, rectangle);
}

To draw multiple bounding boxes, store multiple points and draw with a loop.

private void pBoxCenter_Paint(object sender, PaintEventArgs e)
{
    foreach (Rectangle rectangle in rectangleList)
        e.Graphics.DrawRectangle(pen, rectangle);
}

Use Invalidate method at the appropriate time to refresh the picture box, so you just need modify the rectangles in the list to move or resize them. for example:

private void pBoxCenter_MouseDown(object sender, MouseEventArgs e)
{
    isMoving = true;
    rectangleList.Add(new Rectangle(e.X, e.Y, 0, 0));
}

private void pBoxCenter_MouseMove(object sender, MouseEventArgs e)
{
    if(isMoving)
    {
        var lastRect = rectangleList[rectangleList.Count - 1];
        rectangleList[rectangleList.Count - 1]
            = new Rectangle(lastRect.X, lastRect.Y, e.X - lastRect.X, e.Y - lastRect.Y);
        pBoxCenter.Invalidate();
    }
}