RE: Positioning text within a circle
- From: "Ken Perry" <whistler@xxxxxxxxxxxxx>
- To: <programmingblind@xxxxxxxxxxxxx>
- Date: Sun, 8 Feb 2009 12:04:03 -0500
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 <mailto:whistler@xxxxxxxxxxxxx>
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
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