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diff --git a/ppmtoilbm.html b/ppmtoilbm.html index b94c31a8..c6144e96 100644 --- a/ppmtoilbm.html +++ b/ppmtoilbm.html @@ -2,7 +2,7 @@ <html><head><title>Ppmtoilbm User Manual</title></head> <body> <h1>ppmtoilbm</h1> -Updated: 28 June 2015 +Updated: 15 January 2022 <br> <a href="#index">Table Of Contents</a> @@ -156,8 +156,8 @@ compression at a minimum, but is very slow. <dt><b>-map</b> <i>ppmfile</i> <dd>Write a normal ILBM using the colors in <ppmfile> as the -colormap. The colormap file also determines the number of planes, a -<b>-maxplanes</b> or <b>-fixplanes</b> option is ignored. +colormap. The colormap file also determines the number of planes; +<b>-maxplanes</b> and <b>-fixplanes</b> are ignored. <dt><b>-cmaponly</b> @@ -179,7 +179,6 @@ this allows row-by-row operation on HAM images, and all HAM images of the same depth (no. of planes) share a common colormap, which is useful for building HAM animations. - <h2 id="references">REFERENCES</h2> Amiga ROM Kernel Reference Manual - Devices (3rd Ed.) @@ -197,7 +196,25 @@ Addison Wesley, ISBN 0-201-56775-X <p>For about a year in 1993-1994, there was a <b>-savemem</b> option. - +<p>There used to be a <b>-floyd</b> (aka <b>-fs</b>) option that was supposed + to cause images to be dithered so that a larger number of colors in the PPM + input could be represented in a smaller number of colors in the ILBM output. + But it was never documented. Furthermore, developers discovered in January + 2022 that the code for this was nonfunctional because of defects, and had + been for a very long time and maybe always. Finally,, this functions is not + appropriate in the Netpbm philosophy, because dithering should be done by a + separate dithering program, not a format conversion program. Indeed, + the programs <b>ppmdither</b>, <b>pnmquant</b>, and <b>pnmremap</b> can do + this. + +<p>Therefore, since Netpbm 10.98 (March 2022), the dithering code has not been + in the program and any attempt to use the options fails with a simple + invalid option message. But the <b>-nofloyd</b> and <b>-nofs</b> options + remain, doing nothing as they were designed to do, and still not documented. + This is just in case something uses those options, since the cost of + maintaining them is so small. + + <h2 id="authors">AUTHORS</h2> <p>Copyright (C) 1989 by Jef Poskanzer. |