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Diffstat (limited to 'pnmremap.html')
| -rw-r--r-- | pnmremap.html | 24 |
1 files changed, 23 insertions, 1 deletions
diff --git a/pnmremap.html b/pnmremap.html index 6343f43c..9a8d7fb9 100644 --- a/pnmremap.html +++ b/pnmremap.html @@ -18,6 +18,8 @@ pnmremap - replace colors in a PNM image with colors from another set [<B>-floyd</B>|<B>-fs</B>|<B>-nfloyd</B>|<B>-nofs</B>] +[<b>-norand</b>] + [<B>-firstisdefault</B>] [<B>-verbose</B>] @@ -193,7 +195,6 @@ adjacent, to a palette that contains only black and white, it might result in an output of black, black, white, white. Pixel-by-pixel mapping would instead map both the gray pixels to the same color. - <p>Floyd-Steinberg gives vastly better results on images where unmodified quantization has banding or other artifacts, especially when going to a small number of colors such as the above IBM set. @@ -204,6 +205,27 @@ synonym for <B>-nofloyd</B>. <P>The default is <B>-nofloyd</B>. + +<dt><b>-norandom</b> + +<dd>This option affects a detail of the Floyd-Steinberg dithering process. +It has no effect if you aren't doing Floyd-Steinberg dithering. + +<p>By default, <b>pnmremap</b> initializes the error propagation +accumulator to random values to avoid the appearance of unwanted +patterns. This is an extension of the original Floyd-Steinberg +algorithm. + +<p>A drawback of this is that the same <b>pnmremap</b> on the same +input produces slightly different output every time, which makes +comparison difficult. + +<p>With <b>-norandom</b>, <b>pnmremap</b> initializes the error +accumulators to zero and the output is completely predictable. + +<p><b>-norandom</b> was new in Netpbm 10.39 (June 2007). + + <DT><B>-firstisdefault</B> <DD>This tells <b>pnmremap</b> to map any input color that is not in |