I need the bounding algorithm for a 2D arc. I have the following
parameters available.

starting point of the arc -> x,y

start angle of the arc (measured clockwise) -> startAngle

swing angle of the arc (measured clockwise from start angle) -
swingAngle

width radius = wR
height radius = hR

I couldn't figure out the earlier algorithms posted.

Can someone help?

Mukund wrote:
It should explain things a lot better. I am trying to draw that
shape on a device and the only drawing function available requires the
bounding rectangle of the arc and the start and swing angles.

Hi,

I didn't get the meaning of the parameters either from the original post
nor from the link. An image could help here to explain..

I gt the feeling that he isn't talking circles but means ellipses

Hi,

I didn't get the meaning of the parameters either from the original post
nor from the link. An image could help here to explain..

I gt the feeling that he isn't talking circles but means ellipses
oriented with major and minor axes in the horizontal and vertical
directions. Like the 'circle select' as used in photoshop for example.

Mike

It should explain things a lot better. I am trying to draw that
shape on a device and the only drawing function available requires the
bounding rectangle of the arc and the start and swing angles.

Mukund wrote:
It should explain things a lot better.   I am trying to draw that
shape on a device and the only drawing function available requires the
bounding rectangle of the arc and the start and swing angles.

Hi,

I didn't get the meaning of the parameters either from the original post
nor from the link. An image could help here to explain..

--http://kaba.hilvi.org

Well the image loads in Firefox if you directly link to it.  So that
link is below.

http://www.documentinteropinitiative.org/implnotes/loadimage.aspx?ima...

--------------------------------------

I tried the following approach assuming that the ellipse that contains
the arc is restricted along either the X-Axis or the Y-Axis.

Using the general parametric form.

h, k = center point of ellipse.
x(t) = h + a.cos(t).cos(o) - b.sin(t).sin(o)
y(t) = k + a.cos(t).sin(o) + b.sin(t).cost(o)

where (o) is either 0 or 90 degrees (angle between X axis and
alignment of ellipse) and (t) is the angle for a point of interest.

Given the fact that the ellipse is axis aligned, a = max(wR, wH), b > min(wR, wH).  a = semi major axis, b = semi minor axis.

I calculated the center of the ellipse (h, k) as below as the starting
angle(startAngle) and the starting point of the arc (startX, startY)
are known.

h = x(t) - (a.cos(t).cos(o) - b.sin(t).sin(o))
k = y(t) - (a.cos(t).sin(o) + b.sin(t).cos(o))

from the above equations.

For horizontal alignment.
Major intercepts: ( h + a,k), ( h – a,k) Minor intercepts: ( h,k + b),
( h,k – b)
Bounding box = (h - a, k -b) x (h + a, k + b)

For vertical alignment
Major intercepts: ( h, k + a) ( h, k – a) Minor intercepts: ( h + b,
k) ( h – b, k)
Bounding Box = (h - b, k - a) x (h + b, k + a)

------------------

Having said that, the vertically aligned ellipses don't work
correctly.   I am trying to figure out what I am doing wrong.  Any
ideas?

Having said that, the vertically aligned ellipses don't work
correctly. I am trying to figure out what I am doing wrong. Any
ideas?