Polygon's share of its rectangle inconsistent?

[Dar Scott]

lineSize?

(aka border size)


On Jun 6, 2013, at 5:39 PM, David Epstein wrote:

> 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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