# Re: Patch for sane.tex (image polarity)

From: Nick Lamb (njl98r@ecs.soton.ac.uk)
Date: Mon Oct 02 2000 - 22:42:39 PDT

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  On Sat, Sep 30, 2000 at 07:56:25PM -0700, David Mosberger-Tang wrote:
  > >>>>> On Sat, 30 Sep 2000 17:13:15 +0200, Henning Meier-Geinitz <hmg-ml@gmx.de> said:
  >
  > Henning> For all other bit depths, larger values mean more red,
  > Henning> green, blue, or white.
  >
  > This is potentially very confusing. Depending on whether you're
  > dealing with a subtractive or additive color synthesis, "more color"
  > could mean darker or brighter, respectively. I no expert in color
  > theory, but perhaps "larger values correspond to more luminous
  > (``brighter'') pixels" would be more accurate and but still clear?

  No experts here, I will crib from the TIFF documentation, while trying
  to stay with SANE's terminology. Actually I think there's little risk
  of people trying to do image acquisition with subtractive color models
  (think about it). How about:

  In frames of type SANE_FRAME_GRAY, when the bit depth is 1 there are
  only two sample values possible, 1 represents minimum intensity (black)
  and 0 represents maximum intensity (white).
  For all other bit depth and frame type combinations, a sample value of 0
  represents minimum intensity and larger values represent increasing
  intensity.

  (I think TIFFs choice of vocabulary "intensity" is appropriate because
  just what /is/ brighter about more xray radiation or infrared?)

  Actually, can anyone tell me (from practical experience) whether I
  am right that this only affects SANE_FRAME_GRAY? Do we have devices
  that actually send 1bit RGB frames?

  Nick.

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