# Re: sane_get_parameters before sane_start

From: Oliver Rauch (oliver.rauch@rauch-domain.de)
Date: Mon Mar 05 2001 - 13:19:39 PST

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  Frederik Ramm wrote:
  >
  > Hi,
  >
  > in the SANE spec it says:
  >
  > > While setting up the device, it is also admissible to call
  > > sane_get_parameters() to get an estimate of what the image
  > > parameters will look like once image acquisition begins.
  >
  > Does that mean in the backend I have to calculate the scan width in
  > pixels, the bytes per line value, etc. every time the user changes an
  > option? Until now, I was planning to do these calculations only once,
  > in sane_start, but that would mean that you'll get meaningless results
  > from sane_get_parameters() unless sane_start has already been called.

  When sane_start has been called sane_egt_parameters has to return
  exact values. sane_get_parameters can be called befor sane_start
  and in this case the values should be correct too, if they are not exact
  that have to be as close as possible to the correct values.

  Bye
  Oliver

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