Path: utzoo!attcan!uunet!lll-winken!ames!ncar!gatech!bloom-beacon!bu-cs!encore!cloud9!cme
From: cme@cloud9.Stratus.COM (Carl Ellison)
Newsgroups: comp.graphics
Subject: Re: the word "bitmap"
Summary: When two worlds collide
	...
	let's label the world we're speaking from/for
Message-ID: <3155@cloud9.Stratus.COM>
Date: 10 Jan 89 20:10:45 GMT
References: <450@orbit.UUCP> <1198@hydra.riacs.edu> <1304@luth.luth.se>
Organization: Stratus Computer, Inc., Marlboro, MA
Lines: 62

In article <1304@luth.luth.se>, sow@ulmo1.mt.luth.se (Sven-Ove Westberg) writes:
> 
> Pixmap is NOT the term we should use for this type of data structures.
> 
> From ISO/DIS 8613-7, "Information processing - text and office systems -
> Office Document Architecture (ODA) and interchange format -
> 
> pel array: A two-dimensional array of pels (Picture Elements) used to
> represent a pictorial image.
> 
> bitmap: A two- or three-dimensional data field representing a pel array.
> 
> In section 9.1 "Bitmap encoding scheme"
> 
> Each element in a pel array may have one of two distinct states.
> These are the set state, corresponding to foreground colour and the
> unset state, corresponding to the background colour. For the purpose of
> representing such an array within a text unit, each pel may be
> represented by a single bit which has the value '0' or '1' depending
> on the state of that pel. .....
> 


There are two worlds trying to intercommunicate here.  Each has its own
dictionary and, unfortunately, citizens of each fail to identify their
worlds -- perhaps believing that it's all one world called Computer Graphics.


One world came from a background of alphanumeric CRT terminals which evolved
into one bit per pixel directly addressable frame stores -- and, voila', people
called that Graphics Mode.  In this world (the one quoted above and the one
using "bitmap"), the primitive graphics operation was the storing of a value
into a pixel (originally setting or clearing of a bit; later setting a 4-bit
color code (looked up in a color map for display)).  Hand someone from this
world a 24-bit per pixel RGB display and s/he'll set 24 bit pixel values and
declare that that's "doing graphics".

In that world it is.

The other world (mine) came from a background of image processing and vector
algebra.  To us, (eg., E&S in the old days), any direct manipulation of a
pixel is not graphics and a screen backed up by a single bit per pixel (eg.,
a Mac or Sun monochromatic screen) is not a graphics output device.  To us,
graphics is the creation of images from mathematically defined objects in
a vector space -- especially via transformation, projection, ....  In this
world, there are no operations directly on individual pixels and the only
raster output worth its salt has to be filtered (therefore multiple bits per
color at each pixel).

In my world, "bitmap" (or "pixmap") is a foreign term.  It comes from those
other folks who directly manipulate the pixels on screen.

Meanwhile, to me as a mathematician, both "bitmap" and "pixmap" are improper
because the word "map" makes no sense.  In both math and computer science,
"map" means a device, table, algorithm, ..., for mapping from one domain to
another.  (To Boy Scouts, it's a piece of paper with squiggles on it -- but
that doesn't fit this case either.)


--Carl Ellison          ...!harvard!anvil!es!cme    (normal mail address)
                        ...!ulowell!cloud9!cme      (usenet news reading)
(standard disclaimer)