OpenEuphoria

Re: finding if point is inside irregular rectangle

• Posted by Dan Moyer <DANIELMOYER at prodigy.net> Feb 25, 2002
• 417 views

Tone,

What is the type & range of values for the points to test and of the corners
of your quadrilateral?  Are they non-integer, like when you were interested
in finding if points were inside a normal rectangle?

I ask because for integers within a certain range of values (video screen
settings), there is a very easy way to tell if a candidate point is within a
polygon of any shape at all.  You just draw the polygon on a non-displayed
screen, filled with some color other than background, and then test if the
point in question is that color.  It's probably not fast, but it's easy.

Dan Moyer

----- Original Message -----
From: <tone.skoda at siol.net>
To: "EUforum" <EUforum at topica.com>
Sent: Monday, February 25, 2002 11:22 AM
Subject: finding if point is inside irregular rectangle



Here's another problem: I need to find out if point lies inside
an irregular rectangle. Irregular rectangle has
4 corners but they don't need to be 90 degree, although they can still be.

Example of irregular rectangle:

     Please view in a fixed-width font such as
                    Courier.


         |--
         |  ----
        |       ---
        |          ----
       |               ---
       |                  ----
      |                       -\
      |                         \\
      |                           \
     |                             \
     |                              \\
    |                                 \
    |                                  \
   |                                    \\
   |------                                \
          -----------                      \
                     ----------             \\
                               -----------    \
                                          -----\


Below is function which needs to be finished. I would do it myself but I'm
not too good at math.

-- bounds parameter should define 4 points of rectangle and should have
these members:
-- 1,2: left_top_x, left_top_y,
-- 3,4: left_bottom_x, left_bottom_y,
-- 5,6: right_top_x, right_top_y,
-- 7,8: right_bottom_x, right_bottom_y.
function is_point_in_irregular_rect (sequence point, sequence bounds)
    -- This is returned.
    integer is_point_in_rect
    -- TODO
    return is_point_in_rect
end function