Hi David,
Would it help if you could calculate the area of the polygons?
The following determines the area of any singly connected (the area of a figure
8 is zero) closed polygon:
on mouseUp
put the points of grc "polygon" into tPoints
put line 1 of tPoints into tStart
put the number of lines in tPoints into n
put 0 into tArea
repeat with i = 1 to n-1
put line i+1 of tPoints into tEnd
put item 1 of tStart - item 1 of tEnd into tWidth
put (item 2 of tStart + item 2 of tEnd)/2 into tHeight --The average
height of this line.
add tWidth * tHeight to tArea
put tEnd into tStart
end repeat
put tArea into msg box
end mouseUp
Jim
>
> Message: 7
> Date: Thu, 6 Jun 2013 19:39:25 -0400
> From: David Epstein <dfepst...@comcast.net>
> To: use-livecode@lists.runrev.com
> Subject: Polygon's share of its rectangle inconsistent?
> Message-ID: <5e916091-0fde-4c67-9d52-04601757a...@comcast.net>
> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
>
> In order to properly adjust the relative area of two dissimilar
> polygons, I thought I would use a function to determine the fraction
> of each polygon's rectangle that is covered by the polygon.
>
> function coverage obLID
> set the filled of obLID to true
> put the rect of obLID into r
> repeat with x = (item 1 of r) to (item 3 of r)
> repeat with y = (item 2 of r) to (item 4 of r)
> put x,y into pt
> if within(obLID,pt) then add 1 to isIn
> add 1 to all
> end repeat
> end repeat
> return isIn/all
> end coverage
>
> This seems to work as expected, but I am perplexed by the fact that
> when I resize an object keeping its proportions constant (drag a
> corner with the shift key down; or script this) I get a surprising
> variation in the result. E.g., a fairly simple shape I tried went
> from 0.48 coverage up to 0.59 coverage when I shrank its dimensions
> by about two-thirds. With tens or hundreds of thousands of pixels
> being sampled in the calculation, I would not expect this variation.
>
> Many thanks for any insights or suggestions.
>
> David Epstein
> *************************
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