CLIM mail archive


Image Processing in CLIM

    Date: Mon, 2 Mar 1992 14:48 EST
    From: Jonathan Bachrach <!>

    We are thinking about porting OBVIUS (Object-Based Vision and Image
    Understanding System) to CLIM.  In order to do this we need precise
    control over color rendering.  It isn't clear in the CLIM 1.0
    document whether CLIM supports the functionality we need.  Here is
    what we need.  

    8-Bit Color Systems: We need to have enough control over the color
    table such that when we ask for a color, we either get it or get a
    condition.  What we need to avoid is asking for a particular color and
    then getting the closest color already in the color table.  What sort
    of support is there for this situation?  It seems that

      (clim:draw-design (clim:make-pattern array colors) medium) ; p154

    would work ok if (A) it were implemented (p154 says that this
    technique is not supported in the present implementation) and (B) it
    would use the colors you ask for and not closest approximations
    already in color-map.  Is this implemented?  If not, when or what
    other support is there for drawing 8-bit images?  Also I'm concerned
    about efficiency here, it appears that this might be inefficient to
    have to load the color-map each time draw-design is called.


    -- jonathan

We've been using CLIM 0.9 for porting Janus CL -- an electronic CAD tool -- to
Symbolics and Sun SPARCstation platforms.  This application requires explicit
control over all 256 entries in the colormap for an 8 bit color system.  Because
I had access to the source code, I was able to get what I needed by implementing
my own color objects and modifying several implementation specific graphics
routines.  Neither CLIM 0.9 or 1.0 seemed to provide explicit control over the
assignment of colors to pixel values.  I haven't gotten a look at the CLIM 2.0
specification as of yet, but it sounds to me that there too the control over the
color map will not be sufficiently explicit.

Just putting in my own two cents to see if other people have the same


Tim Blackman                   Analog Devices Inc.        181 Ballardvale St.
(617) 937-1104                 Wilmington, MA 01887


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