Chris Carroll-Davis wrote:
Dave -
Thanks so much! Yes, your routine is much faster than mine... though
I'm not sure why!!
Here is my code:
on mouseUp
put alphadata of image "black" into temp
put the milliseconds into tStart ## for speed calc
repeat with n = 1 to number of chars in imagedata of image "A1"/4
put char n*4 of imagedata of image "A1" into char n of temp
end repeat
put the milliseconds - tStart && length(tMaskData) ##speed score
set alphadata of image "black" to temp
end mouseUp
For some reason, even though my loop is only a quarter of the length
of yours with just one line of code in it (and no decisions) it is
much slower. It was slower still because I was (for daft reasons I
wont go into!) originally doing the loop backwards.
Two obvious possible reasons .... and probably more that I didn't
immediately see.
1. I suspect taking the imagedata of the image may take some time, so
instead of
repeat with n = 1 to number of chars in imagedata of image "A1"/4
put char n*4 of imagedata of image "A1" into char n of temp
I would have done
put the imagedata of image "A1" into tImageData
repeat with n = 1 to number of chars in imagedata of image "A1"/4
put char n*4 of tImageData into char n of temp
2. Putting a value into "into char N of tVar" happens quickly - but
slower that putting "after tVar"
so I'd actually make that central line be
put char n*4 of tImageData after temp
This might still be slower than the other method, because "repeat for
each char ..." is very fast - possibly fast enough that going around the
loop 4 times as often beats the cost of accessing "char N*4"
--
Alex Tweedly http://www.tweedly.net
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