GDI+ Transormations

[Fabio]

Hi all!

A question about transformations .

Let's have this piece of code that transforms the coordinates of the
Graphics object:

---------
Graphics g = e.Graphics;
Matrix m = g.Transform;
m.RotateAt(45, new Point(100, 100));
g.Transform = m;
g.DrawRectangle (Pens.Blue, 50, 50, 100, 100);
---------

This works, ok.
But let's say that I need to get if a point falls into the transformed
rectangle, i.e.:

Rectangle r = new Rectangle(50, 50, 100, 100);
Console.Write(r .Contains(55, 55);

Obviously, this fails, since the point is computed with the "normal"
coordinates.
There is a way to transform also the coordinates of the control surface?

Thanks!

--

Free .Net Reporting Tool - http://www.neodatatype.net

[Martijn Mulder]

Re: GDI+ Transormations

> A question about transformations .[color=blue]
>
> Let's have this piece of code that transforms the coordinates of the
> Graphics object:
>
> ---------
> Graphics g = e.Graphics;
> Matrix m = g.Transform;
> m.RotateAt(45, new Point(100, 100));
> g.Transform = m;
> g.DrawRectangle (Pens.Blue, 50, 50, 100, 100);
> ---------
>
> This works, ok.
> But let's say that I need to get if a point falls into the transformed
> rectangle, i.e.:
>
> Rectangle r = new Rectangle(50, 50, 100, 100);
> Console.Write(r .Contains(55, 55);
>
> Obviously, this fails, since the point is computed with the "normal"
> coordinates.
> There is a way to transform also the coordinates of the control surface?[/color]



Bob Powell addresses this point in one of his excellent tutorials:

http://www.bobpowell.net/manipulate_graphics.htm

[Fabio]

Re: GDI+ Transormations

"Martijn Mulder" <i@m> ha scritto nel messaggio
news:445881cf$0 $23336$dbd45001 @news.wanadoo.n l...


[color=blue]
>
> Bob Powell addresses this point in one of his excellent tutorials:
>
> http://www.bobpowell.net/manipulate_graphics.htm[/color]

Wow, works great!

Thanks!

Jast a question: I don't understand why in this case I need to do a
Matrix.Invert() while it is not required when I draw on the Graphics.

[Stoitcho Goutsev \(100\)]

Re: GDI+ Transormations

Fabio,

Transformations are applied when you draw and they don't affect the data in
the Rectangle object.

I have two suuggestion:
1. Add the rectangle to a GraphicsPath, apply the transformation on the
graphics path (this will modify the coordinates inside the path) and now use
IsVisible or IsOutlineVisibl e GraphicsPath method to hit test.
2. Create a Matrix that does the oposite inversion (form trasnformed
coorinates to normal (not-trasnformed) and apply the trasnformation on the
the point you want to hittest against and then check with the rectangle.

Matrix m = new Matrix();
m.RotateAt(90, new Point(100, 100));
m.Invert();

Rectangle r = new Rectangle(50, 75, 100, 50);
Point[] pts = new Point[]{new Point(100,50)};
m.TransformPoin ts(pts);
Console.Write(r .Contains(pts[0]));


--
HTH
Stoitcho Goutsev (100)

"Fabio" <znt.fabio@virg ilio.it> wrote in message
news:eKKyyYpbGH A.3856@TK2MSFTN GP03.phx.gbl...[color=blue]
> Hi all!
>
> A question about transformations .
>
> Let's have this piece of code that transforms the coordinates of the
> Graphics object:
>
> ---------
> Graphics g = e.Graphics;
> Matrix m = g.Transform;
> m.RotateAt(45, new Point(100, 100));
> g.Transform = m;
> g.DrawRectangle (Pens.Blue, 50, 50, 100, 100);
> ---------
>
> This works, ok.
> But let's say that I need to get if a point falls into the transformed
> rectangle, i.e.:
>
> Rectangle r = new Rectangle(50, 50, 100, 100);
> Console.Write(r .Contains(55, 55);
>
> Obviously, this fails, since the point is computed with the "normal"
> coordinates.
> There is a way to transform also the coordinates of the control surface?
>
> Thanks!
>
> --
>
> Free .Net Reporting Tool - http://www.neodatatype.net
>[/color]