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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