Chris, when I first came to Rev from HC, I also ignored the 'repeat
for....' loop for quite a long time. Not anymore, though. It's so
much faster that it's usually worth whatever extra code (counters
etc.) that you need to put inside it. As you've found, it can make
the difference between something being practical to do and not.
Just bear in mind that when you do:
repeat for each line L in someList
doSomething with L
L is not to be changed, or you are messing with the loop variable,
and will get 'unexpected' results, so a typical use might be
repeat for each line L in someList
put L into temp -- copy L into a temporary
variable
add 4 to item 3 of temp -- modify as desired
put temp & cr after newList -- store modified line in new list
end repeat
delete char -1 of newList -- delete trailing cr from new list
There must be a huge number of loops that follow this basic theme in
all the Rev made software out there.
Best,
Mark
On 5 Jul 2006, at 10:53, Chris Carroll-Davis wrote:
Jim -
I'm sure you are correct here. I tried testing my loop against
Dave's. On a small image my loop was 75 times slower than his. On
a larger image that took about a third of a second with his
routine, I expected mine to take about 20 seconds... After 5
minutes I gave up!!!
Chipp - your compositing stack is great - wish I'd seen it a few
days ago!
With everyone's help I now have a first draft of handler that
correctly exports a transparent PNG of a field containing Japanese
text - just what I needed! (And I've also learned a couple of
scripting lessons to boot - I had never used the "repeat for each
+var" syntax before! Doh! I am a SC dinosaur and I don't think SC
has this variant). Thanks so much.
All I need now is a bigger brain.
- Chris
On 5 Jul 2006, at 07:27, Jim Ault wrote:
The key maybe the
repeat for each
which is a sequential access rather than
'evaluate the access position each loop'
I also think that the larger the data source, the slower 'repeat
with x ='
becomes.
Try these runs and see if the results are linear or exponential.
get ( number of chars in imagedata of image "A1"/4)
repeat with n = 1 to it/10
repeat with n = 1 to it/5
repeat with n = 1 to it/4
repeat with n = 1 to it/2
repeat with n = 1 to it/1
Jim Ault
Las Vegas
On 7/4/06 2:33 PM, "Chris Carroll-Davis" <[EMAIL PROTECTED]>
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.
I'll try to tweak to improve speed further, but even as it stands I
think it should be fine.
Also, thanks Ken for the links. They helped me understand what is
going on now!
Regards,
Happy Chris
On 4 Jul 2006, at 18:10, Dave Cragg wrote:
I'm not sure what calculations you are doing in the loop, but it
sounds too slow. The following routine creates alphaData from a 300
x 300 grayscale image in less than a second on my not so fast
machine. (You'll probably need to substitute the calculation inside
the loop with your own.)
I'm sure others will step up with faster alternatives. :-)
on mouseUp
put the imageData of image 1 into tImageData
put the milliseconds into tStart ## for speed calc
put 0 into tCount
repeat for each char tChar in tImageData
add 1 to tCount
if tCount = 4 then
put numToChar(255 - charToNum(tChar)) after tMaskData
put 0 into tCount
end if
end repeat
put the milliseconds - tStart && length(tMaskData) ##speed score
set the alphaData of image 1 to tMaskData
end mouseUp
Cheers
Dave
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