[mapserver-users] Performance implications of OFFSITE usage?

[Frank Warmerdam]

Ed McNierney wrote:
> Now that I'm halfway through this I'm doubting the wisdom of it.  My
> motivation was that the use of the OFFSITE parameter was forcing
> MapServer to examine the value of every pixel rather than just process
> them in bulk.  Avoid this should be a performance win.  I'm now
> wondering whether that's a bogus assumption; when rescaling the source
> TIFFs to produce the output image, enough pixel-level processing must be
> going on that the OFFSITE comparison could be a trivial impact.

Ed, 

The drawGDAL and drawTIFF cases in mapraster.c are effectively always
checking for offsite values whether you set it or not, so the answer to your
questions is that no ... MapServer does not incur any significant performance
cost when you use offsite values. 

Best regards,

---------------------------------------+--------------------------------------
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent