I don’t think that will work for what he wants. He I think is
saying if he has rectangle not in the midpoint but anywhere in the
circle he wants to know if it goes outside the circle. This takes a
bit different work then you have done here I think.
Ken
From: programmingblind-bounce@xxxxxxxxxxxxx [mailto:programmingblind-bounce@xxxxxxxxxxxxx
] On Behalf Of E.J. Zufelt
Sent: Sunday, February 08, 2009 1:06 AM
To: programmingblind@xxxxxxxxxxxxx
Subject: Re: Positioning text within a circle
Good evening Ian,
It's been a while since I had to do anything like this.
If I understand correctly you need to determine if any particular
point (p) is outside of the circle.
1. You need to calculate for the right angle triangle formed between
the midpoint of the circle, the point that you are testing, and
either the intersect of that point on the x or y axis.
2. You know the hight of the triangle, and the width of the triangle
(calculated by the distance your point is vertically and
horizontally from the midpoint of the circle.
3. You know that the maximum hypotenus of the triangle is the radius
of the circle, if the hypotenus is greater than the radius then the
point is outside of the circle.
Example:
A circle with radius of 10 and midpoint (20, 20), testing for point
(10, 10).
height = 20 - 10 = 10
Width = 20 - 5 = 15
Hypotenus = sqr(10^2 + 15^2)
hypotenus = sqr(100 + 225)
Hypotenus = sqr (325)
Hypotenus = roughly 18
Since the hypotenus is greater than the radius of the circle then
the point is outside of the circle.
HTH,
Everett
On 8-Feb-09, at 1:28 AM, Ian D. Nichols wrote:
Hi Ken,
Thanks very much for your reply.
Unfortunately I didn't make it clear that I do not want to centre
the text in the circle. I want to place text anywhere in the circle
and make sure that no part of the text accidentally lands outside
the circle. What I need to obtain, or calculate for myself, are the
coordinates of a sufficient number of points on the dircumference so
that I can check to see that the corners of the rectangle containing
the text are all within the circle. I have that logic worked out
already. What I am lacking are the numbers to compare the
coordinates of the text with.
I recognize that it is a rather complicated procedure. Windows must
know how to do it because the ellipse function with equal x and y
axes draws a perfect circle.
I've calculated the coordinates of the 4 points where the diagonals
intersect the circumference, and I did it using the theorem of
Pythagarus, as you did in your reply. But only the diagonals of the
circle's bounding square coincide with the hypotenuses of right-
angled triangles, so that method is very limited in what it can do.
Thanks again. I live in hope!
All the best,
Ian
Ian D. Nichols,
Toronto, Canada
----- Original Message -----
From: Ken Perry
To: programmingblind@xxxxxxxxxxxxx
Sent: Saturday, February 07, 2009 9:07 PM
Subject: RE: Positioning text within a circle
Ok you can use the formula s1^2+s2^2=h^2 to make sure your
rectangles cross hypotenuse fits as the diameter of the circle.
From there you just need to place the center point of the rectangle
in the middle of the circle. So just Using small numbers I will say
that your long side is 4, your short side is 3 and your circle is 5
diameter. We can find if the rectangle has the same diameter by
doing:
3^2 +4^2 =5^2 Which it does. Most of the circle drawing functions I
have used draw the circle from a midpoint so you
drawCircle(10+l/2,10+s/2))
When you print the text starting at upper left hand corner of the
box 10,10 you should get it in the center
So if I am being confusing the thing I am doing is splitting your
rectangle into two right triangles. Finding the hypotenuse which
will criss cross the rectangle right in the middle. That becomes
both the center point of the rectangle and the circle. It also will
be the diameter of the circle and the rectangle. So if your
hypotenuse fits as the diameter then it fits. Then its just simply
finding the center and calculating where to place the first part so
the centers of the rectangle and the circle corresponds. If you
need help and I am being too confusing just send me your circle
drawing function and text writing function and I will try and help
you out.
Ken
From: programmingblind-bounce@xxxxxxxxxxxxx [mailto:programmingblind-bounce@xxxxxxxxxxxxx
] On Behalf Of Ian D. Nichols
Sent: Saturday, February 07, 2009 6:57 PM
To: program-l@xxxxxxxxxxxxx; programmingblind@xxxxxxxxxxxxx
Subject: Positioning text within a circle
Hi Listers,
I have a circle drawn on the monitor screen. I know its diameter
and its centre point in screen pixels.
I want to make sure that text I draw on the screen is completely
within this circle. I use the TextOut function, which uses a POINT
sructure for positioning the text. I can use GetTextExtentPoint32
to calculate the size and location of the enclosing rectangle of the
text. I need to make sure that all four of the corners of that
rectangle are going to fall within the circle.
Can some one please tell me how I can determine the location of the
circumference of the circle, so that I can check that my text
rectangle will fall completely within it? I'm more than 50 years
out of high school, and didn't study mathematics or geometry, or
whatever it is that I need, at university.
Thanks in advance.
Ian
Ian D. Nichols,
Toronto, Canada