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Jon Lennart Aasenden · Guest

Hello again.

I guess i was not that good at explaining my problem.
I believe it is a simple task, perhaps to simple, for those of you that
replied.
I know Nils has constructed a whole polygon dtp package, so my humble
requirements became perhaps a bit blown out of proportions.

ok, here goes:

ROTATION
=========
Let's say i have a polygon of a 5 pointed star, pointing upwards like a
sherrif's badge.
I would like to rotate the points that make up this star, so (for example)
it points to the right.. or indeed, any degree between 0..359

For example:

type
TAngleRange = 0..359;

(* rotate around itself *)
Procedure RotatePoly(var APoints:Array of TPoint;Const Angle:TAngleRange);

(* rotate around a external fixed point *)
Procedure Procedure RotatePolyEx(var APoints:Array of
TPoint;Origo:TPoint;Const Angle:TAngleRange);

RotatePoly could probably call RotatePolyEx with a center point from the
original polygon.
Does anyone have somthing like this around that does not need a whole
support unit?

SCALING
========

Again, let's assume i have a 5 pointed star as a polygon.
It exists within a rectangle of 10,10 .. 110,110.
I would like to inflate it by say, 6 pixels, so it spans from 4,4..116,116
or deflate it :)

perhaps somthing like:

Procedure InflateRect(var APoints:Array of TPoint;Const Pixels:Word);

One of those that replied mentioned somthing about placing the origo at
x0/y0?
That would mean that the above would look exist within a rectangle of
-50,-50 .. 50,50 right?

While i understand the logic of it, (left & top is negative, right bottom is
positive) i need an example to see the matrix stuff in action. Could anyone
help me out? It would mean a lot.
Math was never my strong side im afraid, i have a learning problem there.

I will ofcourse check out TPolygon32 as a reference and try my best to
understand it.
I seem to remember that Nils had some sort of tutorial for this online?

Kind regards

Jon Lennart Aasenden

Alfred ten Hoeve · Guest

Here is a small unit you can use.

unit Transformations;

interface

uses windows;

type
PointArray = array of TPoint;

TPunt = record // something like TPoint, but now for reals
r : extended;
phi : extended
end;

function Zwaartepunt(InPoints : array of TPoint): TPoint; // Center of
gravity
function Multiply(factor : extended; InPoints : array of TPoint; Center :
TPoint) : PointArray; // scaling
function Rotate(angle : extended; InPoints : array of TPoint; Center :
TPoint) : PointArray;

implementation

uses Math;

function Zwaartepunt(InPoints : array of TPoint): TPoint;
var
i, num : integer;
begin
num := High(InPoints);
Result.X := 0;
Result.Y := 0;
for i := 0 to num do
begin
Result.X := Result.X + InPoints[i].X;
Result.Y := Result.Y + InPoints[i].Y;
end;
Result.X := Round(Result.X / (num+1));
Result.Y := Round(Result.Y / (num+1));
end;

function Multiply(factor : extended; InPoints : array of TPoint; Center :
TPoint) : PointArray;
var
i, num : integer;
Q : array of TPunt;
begin
num := High(InPoints);
SetLength(Result, num + 1);
SetLength(Q, num + 1);
for i := 0 to num do
begin
Q[i].r := factor * sqrt(sqr(InPoints[i].X - Center.X) +
sqr(InPoints[i].Y - Center.Y));
Q[i].phi := arcTan2(InPoints[i].Y - Center.Y, InPoints[i].X - Center.X);

Result[i].X := Round(Center.X + Q[i].r * cos(Q[i].phi));
Result[i].Y := Round(Center.Y + Q[i].r * sin(Q[i].phi));
end;
end;

function Rotate(angle : extended; InPoints : array of TPoint; Center :
TPoint) : PointArray;
var
i, num : integer;
Q : array of TPunt;
begin
num := High(InPoints);
SetLength(Result, num + 1);
SetLength(Q, num + 1);
for i := 0 to num do
begin
Q[i].r := sqrt(sqr(InPoints[i].X - Center.X) + sqr(InPoints[i].Y -
Center.Y));
Q[i].phi := angle + arcTan2(InPoints[i].Y - Center.Y, InPoints[i].X -
Center.X);

Result[i].X := Round(Center.X + Q[i].r * cos(Q[i].phi));
Result[i].Y := Round(Center.Y + Q[i].r * sin(Q[i].phi));
end;
end;

end.

You need to draw the figures yourself.

Hope this helps.
Alfred.

Jon Lennart Aasenden · Guest

Looks like just the thing i was looking for!

Thanks for the help!

Jon Lennart Aasenden

"Alfred ten Hoeve" <Alfred.nospam (AT) nospam (DOT) nl> wrote

John Herbster · Guest

"Jon Lennart Aasenden" <post_nospam_nojunk (AT) jurasoft (DOT) no> wrote