[cl-gd-devel] just to share

[Edi Weitz]

On Tue, 22 Nov 2005 03:54:35 -0800 (PST), arry <frinkofox at yahoo.com> wrote:

> I just want to share a problem with cl-gd or maybe gd itself i don't
> know...
>
> Has anybody tried to draw an ellipse which starts and ends at a
> precise angle?  Well, I have and it turns out that the angles that i
> have specified are not drawn exact , they are either bigger or
> smaller and SOMETIMES theyy are correct!
>
> is this a problem with gd  or cl-gd?
>
> example
> I draw an ellipse that passes through two points then I want this
> ellipse to start from exactly one of the two point aand end at the
> other one. I calculate the angles with tthe help of the function
> (atan) or (asin) using the coordinates of the center of the ellipse
> and the two given points...
>
> and the angles drawn don't match with the given points That's
> funny!!! ridiculous!!!  There's always 1 or 2 maybe more degrees
> discrapency between the angles drawn and the given points

I don't have time to investigate this at the moment but if in doubt
I'd first try with a similar C program to see if the problems are in
GD.  You also might want to check if any rounding errors occur within
CL-GD.

Good luck,
Edi.