Images and Image Data

[Michael Crawford]

Hello,


I have modified my script to produce the appropriate image and it works
perfectly apart from one thing...


The script looks like this. Basically it loops across some tab delimited
data (which is elevation data, that is a height measurement). If that point
is above 0, ie above sealevel it makes it green (ie solid land). If it is 0
or below zero it makes it blue (ie under water)

on mouseUp
  ## get the data
  put fld "data" into tOrigData
  set the itemdelimiter to TAB

  put 571 into twidth -- data is 571 across
  put 429 into tHeight -- data is 429 lines in height

  ## create the image
  create image
  put it into tID

  set the width of tID to tWidth
  set the height of tID to tHeight

  put empty into iData
  repeat with j = 1 to tHeight
    repeat with i = 1 to tWidth
      put item i of line j of tOrigData into tDataValue
      if tDataValue > 0 then  -- above sea level
        put binaryEncode("CCCC",0,0,255,0) after iData ---make green
      else -- point is below sea level
        put binaryEncode("CCCC",0,0,0,255) after iData  --- make blue
      end if
    end repeat
  end repeat
  set the imageData of tID to iData
end mouseUp


The only problem is the speed of execution. It is painfully slow. A bit of
checking reveals that it is the line:

put item i of line j of tOrigData into tDataValue


that is causing the bottleneck. There must be a better way to do this? In
the past I have never really bothered optimising these sort of repeat loops
as it has always been fast enough for me. With 571 x 429 data points though
it is just too slow. Does any one have any suggestions?


Thanks


Michael Crawford