Area of Irregular Polygon
bernd.niggemann at uni-wh.de
Wed Nov 11 20:01:46 EST 2015
for those on the list like me who can only iteratively add 1 to a variable
and that have 10 seconds to spare to get at the area of a polygon:
here is what the screen thinks it is:
put "poly" into pName
if not (there is a graphic pName) then
answer "couldnt find graphic to analyze"
if there is a image "ImageForArea" then delete image "ImageForArea"
put the milliseconds into start
-- set up the graphic for black
put the opaque of graphic pName into tOldOpaque
put the editMode of graphic pName into tOldEdit
put the backgroundcolor of graphic pName into tOldBackground
put the lineSize of graphic pName into tOldLinesize
put the antialiased of graphic pName into tOldAntiAliased
set the opaque of graphic pName to true -- this forces "closure" of
set the backgroundcolor of graphic pName to black
set the lineSize of graphic pName to 0
set the editMode of graphic pName to "none"
set the antialiased of grc pName to false
reset the templateGroup
set the margins of the templateGroup to 0
select graphic pName
export snapShot from the last group to tImg as png
create image "ImageForArea"
set the text of image "ImageForArea" to tImg
put the AlphaData of image "ImageForArea" into tAlphaData
put numToByte(255) into tTransparent -- 0 = transparent
put 127 into tCutOff
put 0 into tBlack
repeat for each byte aByte in tAlphaData
if byteToNum(aByte) > tCutOff then add 1 to tBlack
-- get rid of the image that was analyzed
delete image "ImageForArea"
-- restore the graphic
set the opaque of graphic pName to tOldOpaque
set the backgroundcolor of graphic pName to tOldBackground
set the lineSize of graphic pName to tOldLinesize
set the editMode of graphic pName to tOldEdit
set the antialiased of graphic pName to tOldAntiAliased
put the milliseconds - start into tTime
put "Area is " & tBlack & return \
& tTime & " milliseconds" into field "F1"
reset the templateGroup
here we count the pixel of the alphaData of a snapshot from the graphic that
have a value > 127, i.e. are more than half transparent.
10 seconds is for Hermann's graphic created with testPoints. It is pretty
close to the calculated values.
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