Stretch, Rotate, Rellocate ellipse in C# windows forms

[Dan]

I would like to draw an ellipse on a windows form and through mouse drags
stretch, rotate and relocate the ellipse.

Thanks in advance - Dan

 

[Qu]

I would like to draw an ellipse on a windows form and through mouse drags
stretch, rotate and relocate the ellipse.

Thanks in advance - Dan

Well, I don't know about drawing the ellipse or streching and
rotating, but I made this code recently to relocate an object. It's
not perfect (the object centre jumps to the mouse position), but it
works.

Call this on the MouseMove event of your object:

if (MouseButtons == MouseButtons.Left)
{
mousePoint = /*Your Form/Groupbox Goes
Here*/.PointToClient(new Point(MousePosition.X - /*Your Control Goes
here*/.Size.Width / 2, MousePosition.Y - /*Your Control Goes
here*/.Size.Height / 2));
/*Your Control Goes here*/.Location = mousePoint;
}

You could fix the above mentioned 'jump to mouse' by recording two
offset values on MouseDown, and adding them to the declaration of
mousePoint, replacing the (yourControl.Size.Width / 2) and
(yourControl.Size.Height /2).

On MouseDown ()
{
xOffset = MousePosition.X - /*Your Control Goes
here*/.Location.X;
yOffset = MousePosition.Y - /*Your Control Goes
here*/.Location.Y;
}

Hope this helps,
Qu.

 

[Dan]

Thanks Qu. This is part of the battle but I also really need the resizing and
rotating. Hopefully some other guru will be able to help be out.

Thanks - Dan

 

[Dan]

Your question is fairly vague, so it'd be impossible to offer very
specific advice.

However, for the UI, handling the MouseDown, MouseMove, and MouseUp events
are useful for detecting and tracking mouse input.

For drawing the ellipse, assuming you just want to use the
Graphics.DrawEllipse() method, you'll probably want to set the Transform
property of the Graphics instance you're drawing into before calling
DrawEllipse(). The actual Matrix you use will be initialized based on the
user input, to apply the desired scaling, rotating, and translation.

Pete

Pete,

Yes I would like to use the Graphics.DrawEllipse method. What I was
envisioning was like you see for example in a paint application. You have a
figure on the screen. When it is highlighted you can "grab" the corner to
stretch the figure. I would like to do this with rotation as well and be able
to move the figure. Hope this explains it a bit better....

Thanks - Dan

 

[Dan]

Not really. I mean, I already figured out all of that, and my reply
provided as much information as would be relevant for that degree of
detail.

If you find yourself with specific problems while implementing the mouse
handling and/or ellipse drawing, then please feel free to post the code
you've got, with details about what you expected it to do, what it's
actually doing, and why that's not what you want.

Other than that, there's really nothing more to offer, short of simply
writing the code for you (not something I'm interested in doing right now,
but I suppose you never know...maybe someone else would be).

Pete

How do you create a highlighted object to select?

 

[Dan]

That depends on how you're drawing the object in the first place. And on
what you mean by "highlighted". And on what you mean by "create".

Let's make some assumptions, since you haven't provided any details:

* We've got a data structure that's a collection of ellipses
* Each ellipse includes information as to size, rotation, and position
* We draw each ellipse based on this information whenever our form's
OnPaint() method is called
* We already have code in place to track mouse input
* By "highlighted" you simply mean the ellipse that is current being
adjusted by the user

Then, you'll want a way to identify which of the existing ellipses is the
one that's "highlighted", and when you are drawing all of the ellipses,
draw that one differently to indicate that it's been highlighted.

For the former, you could do it a variety of ways. Such as, keep a
reference to the "selected" object, and compare this "selected" reference
to the current object as you enumerate your collection of ellipses for
drawing. Alternatively, the objects themselves could maintain state with
respect to whether they are selected or not. You'd simply draw each
ellipse differently depending on this state. This alternative technique
has the advantage of more easily supporting multiple selected objects, but
has the disadvantage that your model data now also includes user-interface
state data.

I'm sorry if the above sounds vague. Unfortunately, it's not really
possible to provide specific advice without being presented with a
specific question.

Pete

Thanks Pete. As you can tell I am new to C# and will try to work my way
through this. Thanks for your time.