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diff --git a/pnmquant.html b/pnmquant.html index fe355a3f..61beb2de 100644 --- a/pnmquant.html +++ b/pnmquant.html @@ -2,7 +2,7 @@ <HTML><HEAD><TITLE>Pnmquant User Manual</TITLE></HEAD> <BODY> <H1>pnmquant</H1> -Updated: 09 April 2013 +Updated: 09 February 2019 <BR> <A HREF="#index">Table Of Contents</A> @@ -41,6 +41,26 @@ color map which is generated from the colors in that same input. The options have the same meaning as in those programs. See their documentation to understand <B>pnmquant</B>. +<p>You may actually get fewer than <b>ncolors</b> colors in the output because + the method <b>pnmcolormap</b> uses to choose the best set of colors for the + image is not the same as the method <b>pnmremap</b> uses to determine the + best color from the set to represent an individual color. For example, + <b>pnmcolormap</b> may include salmon in the color map as the best + representative of a pink pixel in the input and include coral in the color + map as the best representative of an actual coral pixel in the input. But + <b>pnmremap</b> is free to use any color in the color map to represent that + pink pixel and would find coral is a closer match for pink than salmon and + therefore use coral for pink. <b>pnmremap</b> might not use salmon + for <em>any</em> pixel. + +<p>This waste of a slot in the color map is a consequence of the approximate + method <b>pnmcolormap</b> uses in order to compute the color map with a + practical amount of computation. + + +<h3 id="separate">Running <b>pnmcolormap</b> and <b>pnmremap</b> Separately +</h3> + <P>It is much faster to call <B>pnmcolormap</B> and <B>pnmremap</B> directly than to run <B>pnmquant</B>. You save the overhead of the Perl interpreter and creating two extra processes. <B>pnmquant</B> is |