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Michelle, I have
explored that topic and reported what I found in “Managing Colours”, a chapter
in “MY (MI) Bag’oTricks”. And my conclusion was that there was something hidden
in the definition of the intermediate colour levels. Assuming
equal spacing between levels would lead at splitting colour components in equal
parts. As any colour is given in RGB by m*R + n*G +B, splitting the code of
each component would give the same colour as splitting the global code in equal
parts. I have tested that on several schemes and comparing calculated values
with what were the actual colours of a thematic map saved in a wor, I concluded
that the mathematical approach gave colours close to the map colours but not
right on. Thus, there must be some other procedure used by MI to determine
those intermediate levels. Do not
think that using the HSV definition would get closer colours than RGB; they are
slightly different but as far off as with RGB. I will be
more than willing to rewrite this part of my book if you (anyone among you)
could come up with a satisfactory answer. Jacques Jacques PARIS e-mail (>>>19.12.00) [EMAIL PROTECTED] For
MapInfo support, see the Paris PC Consult enr. site at http://www.total.net/~rparis/gisproducts.htm For
MapBasic questions see the J.Paris site at http://www.total.net/~jakesp/index.htm -----Original
Message----- Hi, I'm
writing a mapbasic program that gets a "start colour" and and
"end colour" from the user, then works out gradational colours
between those two - exactly the same as the range tool in thematic
mapping utility. (No I can't use that, so yes, I'm re-inventing the
wheel). So far I've got the code to work out the number of colour
variations required, and has worked out the numeric increment that is added to
the "start colour" RGB value to create a succession of new
colours. It works - i.e. I'm sort of seeing a colour variation, except
that I'm getting a variety of tones (i.e the brightness of the colours isn't
gradational), which doesn't look quite right. Anybody gone through this
process before? Or know of a decent resource that will explain the use of
RGB values? (I've read the MapBasic manual - Red x X, Green x Y
etc), but I haven't found that helpful. TIA Michelle Smith |
