Background Colors

[Elisabeth Roche]

Also, in your preferences, options, settings in Netscape 1.1n et al, you
should set for closest in the colour settings....

E Roche ace at opus1.com
serendipity RULES!


At 02:04 PM 3/12/96 -0800, Hillary Handwerger wrote:
>Thank you for that explanation.  I intuitively knew what was going on, 
>but it was good to see a description of the phenomena.
>
>
>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>Hillary Handwerger
>hillaryh at sme.org
>Society of Manufacturing Engineers-- CoNDUIT Project
>313 271-1500 ext 597 
>+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
>
>
>On Tue, 12 Mar 1996, JQ Johnson wrote:
>
>> kjustie at mgk.nslsilus.org (Kevin Justie) asks why his background colors
>> (that look fine on a Mac) appear dithered when viewed with Netscape on a
>> PC.  The answer is slightly complex.  Basically, the problem is that not
>> all colors an author might want are available; the display hardware is
>> typically capable of showing only 256 colors on the screen (not just in the
>> window) at a time, and the system reserves some colors, making the set of
>> colors Netscape has available less than 256. Netscape allocates a color
>> cube, normally 6x6x6 (216 colors in all), then if it needs to display a
>> color not in its color cube dithers the image to approximate it using
>> nearby colors in its color cube.  The bottom line is that the only colors
>> likely to be available in Netscape on a PC are those with 00, 33, 66, 99,
>> CC, or FF in each of the red, green, and blue fields of the color triplet
>> (#rrggbb).
>> 
>> Note that this set of 216 colors is a subset of the Mac 8-bit "system
>> colors", so using these colors is also good on a Mac.  I believe that on a
>> Mac Netscape normally uses the system color palette.
>> 
>> However, there is additional complexity.  Netscape can't always allocate a
>> 6x6x6 color cube.  The user's PC hardware might not allow 256 colors, or
>> too many colors might be reserved for other purposes.  In that case, older
>> versions of Netscape for the PC (I haven't checked 2.0) reserved a smaller
>> color cube.  And some versions of Netscape (old versions for X, for
>> instance) didn't use a color cube at all, but instead used a first-fit
>> algorithm, allocating colors as needed.
>> 
>> Finally, the kicker:   Netscape 1.1 for the PC appears to use a different
>> color cube for backgrounds than what it uses for images.  Netscape 1.1 on
>> the PC doesn't render background colors with "99" in triplets correctly
>> except within images (e.g. as the transparent color).  Instead, it
>> apparently thinks it has, e.g., A0-based triplets available, and dithers
>> other nearby values.  This bug does NOT exist in Netscape 2.0 for the PC.
>> 
>> To return to Justie's posting, #009999 should work fine on most PCs running
>> 2.0, just as it does on most Macs; #BBBBBB may get dithered.  Justie's
>> pages looked fine to me when viewed on a PC running 2.0.  However, sure
>> enough, both #009999 and #BBBBBB look wrong as the background color on PCs
>> running Netscape 1.1.  Given the rapidity that 2.0 is replacing 1.1, I
>> wouldn't worry about the problem if I were Justie.
>> 
>>  JQ Johnson                      office: 115F Knight Library
>>  Academic Education Coordinator  e-mail: jqj at darkwing.uoregon.edu
>>  1299 University of Oregon       voice: 541-346-1746; fax: 541-346-3485
>>  Eugene, OR  97403-1299          <URL:http://darkwing.uoregon.edu/~jqj/>
>> 
>> 
>> 
>