CLIM mail archive


Re: clim contrasting colors

    Date: Fri, 28 Aug 1992 11:45 EDT
    From: (David A. Moon)

    [other recipients deleted]

[Added back again]

    > Date: Thu, 27 Aug 1992 10:52-0400
    > From: Scott McKay <>
    > Subject: clim contrasting colors
    > To: jmorrill@BBN.COM, clim@BBN.COM
    > Cc: faes-dev@BBN.COM,
    > In-Reply-To: <>
    >     Date: Wed, 26 Aug 1992 17:51 EDT
    >     From: Jeff Morrill <jmorrill@BBN.COM>
    >     (clim 1.1, allegro 4.1)
    >     We recently borrowed an interior decorator to decorate our windows.
    >     He decided, for color screens, that the window background should
    >     be clim:+royal-blue+ and the window foreground should be clim:+white+.
    >     I have discovered that these two inks are identical ("white") on a B&W Sun
    >     OpenWindows display.  This makes it rather difficult to use the program.
    > Huh?  This is very odd.

    You may have missed the three key letters "B&W".

    It's true on other platforms, probably all platforms, that some colors that
    contrast on a color display map to the same color on a monochrome display.
    This is just unavoidable as long as absolute colors are used by applications,
    rather than some kind of logical specifications with some semantics to them
    that can be mapped with knowledge of the specific display.  Although another
    set of recent mail in my bloated mailbox seems to indicate that some third
    party Macintosh display controllers lie when you ask them what their color
    palette is.  Grr.

Dave just pointed out that I misread this message, omitted that key
"B&W".  Sorry about that.

What happens when you draw with a color on B&W screen, is that CLIM
generates a stipple that corresponds to the "luminosity" of the color.
Unfortunately, CLIM 1.1 uses a bogus formula for figuring out the
luminosity.  The thing shafting you (Jeff) in this case is that the
CLIM actually stipples (1- luminosity), so that inks that should be dark
come out light!

Anyway, this has been fixed in CLIM 2.0.  You can either work around
this by picking a different background on B&W screens, or I can try to
get a fix to you.  (I'm frantically trying to put together a CLIM 2.0
beta release, so I would obviously prefer for you to work around the
problem for the time being...)


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