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<H1>pnmtopng</H1>
Updated: June 2002
<BR>
<A HREF="#index">Table Of Contents</A>
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<H2>NAME</H2>
pnmtopng - convert a PNM image to PNG
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<H2>SYNOPSIS</H2>
<B>pnmtopng</B>
[<b>-verbose</b>]
[<b>-downscale</b>]
[<b>-interlace</b>]
[<b>-alpha </b><i>file</i>]
[<b>-transparent </b>[<b>=</b>]<i>color</i>]
[<b>-background </b><i>color</i>]
[<b>-palette </b><i>palettefile</i>]
[<b>-gamma </b><i>value</i>]
[<b>-hist</b>]
[<b>-chroma</b> <i>wx wy rx ry gx gy bx by</i>]
[<b>-phys</b> <i>x y unit</i>]
[<b>-text </b><i>file</i>]
[<b>-ztxt </b><i>file</i>]
[<b>-time </b>[<i>yy</i>]<i>yy</i><b>-</b><i>mm</i><b>-</b><i>dd</i>
<i>hh</i><b>:</b><i>mm</i><b>:</b><i>ss</i>]
[<b>-nofilter</b>]
[<b>-sub</b>]
[<b>-up</b>]
[<b>-avg</b>]
[<b>-paeth</b>]
[<b>-compression </b>level]
[<b>-force</b>]
[<b>-version</b>]
[<I>pnmfile</I>]
<?makeman .SH OPTION USAGE ?>
<p>
Obsolete options:
<p>
[<b>-filter </b>type]
<P>You may abbreviate any option to its shortest unique prefix.
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<H2>DESCRIPTION</H2>
<p><b>pnmtopnm</b> reads a PNM image as input and produces a PNG image as
output.
<P>Color values in PNG files are either eight or sixteen bits wide, so
<I>pnmtopng</I> will automatically scale colors to have a maxval of
255 or 65535. Grayscale files will be produced with bit depths 1, 2,
4, 8 or 16. An extra <B>pnmdepth</B> step is not necessary.
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<H2>OPTIONS</H2>
<DL COMPACT>
<DT><B>-verbose</B>
<DD>
Display the format of the output file.
<DT><B>-downscale</B>
<DD>
Enables scaling of maxvalues of more then 65535 to 16 bit. Since
this means loss of image data, the step is not performed by default.
<DT><B>-interlace</B>
<DD>
Creates an interlaced PNG file (Adam7).
<DT><B>-alpha </b> <i>file</i>
<DD> This specifies the transparency (alpha channel) of the image.
You supply the alpha channel as a standard PGM alpha mask (see the <a
href="pgm.html">PGM</a> specification. <b>pnmtopng</b> does not
necessarily represents the transparency information as an alpha channel in
the PNG format. If it can represent the transparency information through
a palette, it will do so in order to make a smaller PNG file.
<b>pnmtopng</b> even sorts the palette so it can omit the opaque colors
from the transparency part of the palette and save space for the palette.
<DT><B>-transparent </b><i>color</i>
<DD>
<B>pnmtopng</B> marks the specified color as transparent in the PNG image.
<P>Specify the color (<i>color</i>) as described for the <a
href="libppm.html#colorname">argument of the <b>ppm_parsecolor()</b>
library routine</a>.
E.g. <B>red</B> or
<B>rgb:ff/00/0d</B>. If the color you specify is not present in the
image, <B>pnmtopng</B> selects instead the color in the image that is
closest to the one you specify. Closeness is measured as a cartesian
distance between colors in RGB space. If multiple colors are
equidistant, <B>pnmtopng</B> chooses one of them arbitrarily.
<P>However, if you prefix your color specification with
"=", e.g.
<pre>
-transparent =red
</pre>
<P> only the exact color you specify will be transparent. If that
color does not appear in the image, there will be no transparency.
<B>pnmtopng</B> issues an information message when this is the case.
<DT><B>-background </b><i>color</i>
<DD>
Causes <b>pnmtopng</b> to create a background color chunk in the PNG output
which can be used for subsequent alpha channel or transparent color
conversions. Specify <i>color</i> the same as for <b>-transparent</b>.
<DT><B>-palette </b><i>palettefile</i>
<DD>This option specifies a palette to use in the PNG. It forces
<b>pnmtopng</b> to create the paletted (colormapped) variety of PNG --
if that isn't possible, <b>pnmtopng</b> fails. If the palette you
specify doesn't contain exactly the colors in the image,
<b>pnmtopng</b> fails. Since <b>pnmtopng</b> will automatically
generate a paletted PNG, with a correct palette, when appropriate, the
only reason you would specify the <b>-palette</b> option is if you care
in what order the colors appear in the palette. The PNG palette has colors
in the same order as the palette you specify.
<P>
You specify the palette by naming a PPM file that has one pixel for each
color in the palette.
<P>
If you have a palette and you want to make sure your PNG contains only colors
from the palette, approximating if necessary, pass the Netpbm input image
and your palette PPM through <b>pnmremap</b>. There's no need to use
<b>-palette</b> on <b>pnmtopng</b> in this case. It doesn't save
<b>pnmtopng</b> any work.
<DT><B>-gamma </b><i>value</i>
<DD>Causes <b>pnmtopng</b> to create an gAMA chunk. This information helps
describe how the color values in the PNG must be interpreted. Without
the gAMA chunk, whatever interprets the PNG must get this information
separately (or just assume something standard). If your input is a true
PPM or PGM image, you should specify <b>-gamma .45</b>. But sometimes
people generate images which are ostensibly PPM except the image uses a
different gamma transfer function than the one specified for PPM. A common
case of this is when the image is created by simple hardware that doesn't
have digital computational ability. Also, some simple programs that generate
images from scratch do it with a gamma transfer in which the gamma value is
1.0.
<DT><B>-hist</B>
<DD>Use this parameter to create a chunk that specifies the frequency
(or histogram) of the colors in the image.
<DT><B>-chroma</b> white point X and Y, red X and Y, green X and Y,
and blue X and Y
<DD>This option specifies the white point and rgb values following
the CIE-1931 spec.
<DT><B>-phys</b> <i>x y unit</i>
<DD>When your image should not be displayed with square but with
rectangular pixels, use this option to create a pHYS chunk. When
<i>unit</i> is 0, <i>x</i> and <i>y</i> give only the ratio of pixel
width and height. When it is 1, <i>x</i> and <i>y</i> specify the
number of pixels per meter.
<DT><B>-text</b> <i>file</i>
<DD>
This option lets you include comments in the text chunk of the PNG output.
<i>file</i> is the name of a file that contains your text comments.
<p>Here is an example of a comment file:
<pre>
Title PNG file
Author Bryan Henderson
Description how to include a text chunk
PNG file
"Creation date" 3-feb-1987
Software pnmtopng
</pre>
<p>The format of the file is as follows: The file is divided into lines,
delimited by newline characters. The last line need not end with a newline
character. A group of consecutive lines represents a comment.
<p>A "delimiter character" is a blank or tab or null character. The
first line representing a comment must not start with a delimiter
character. Every other line in the group is a "continuation line" and
must start with a delimiter character.
<p>The first line representing a comment consists of a keyword and the
first line of comment text. The keyword begins in Column 1 of the
file line and continues up to, but not including, the first delimiter
character, or the end of the line, whichever is first. Exception: you
can enclose the keyword in double quotes and spaces and tabs within
the double quotes are part of the keyword. The quotes are not part of
the keyword. A NUL character is not allowed in a keyword.
<p>The first line of the comment text is all the text in the file line
beginning after the keyword and any delimiter characters after it.
immediately after the delimiter character that marks the end of the
keyword.
<p>A continuation line defines a subsequent line of the comment. The
comment line is all the text on the continuation line starting with the
first non-delimiter character.
<p>There is one newline character between every two comment lines. There
is no newline character after the last line of comment text.
<p>There is no limit on the length of a file line or keyword or comment text
line or comment text. There is no limit on the number of comments or
size of or number of lines in the file.
<DT><B>-ztxt</b> <i>file</i>
<DD>The same as -text, except <b>pnmtopng</b> considers the text compressed.
<DT><B>-time </b> <i>yy-mm-dd hh:mm:ss</i>
or <b>-time </b><i>yyyy-mm-dd hh:mm:ss</i>
<DD>This option allows you to specify the modification time value to be
placed in the PNG output.
You can specify the year parameter either as a two digit or four digit value.
<DT><B>-filter </b><i>type</i>
<DD>This option is obsolete. Before Netpbm 10.22 (April 2004), this was
the only way to specify a row filter. It specifies a single type of
row filter, by number, that <b>pnmtopng</b> must use on each row.
<p>Use <b>-nofilter</b>, <b>-sub</b>, <b>-up</b>, <b>-avg</b>, and
<b>-paeth</b> in current Netpbm.
<dt><b>-nofilter</b>
<dt><b>-sub</b>
<dt><b>-up</b>
<dt><b>-avg</b>
<dt><b>-paeth</b>
<dd>Each of these options permits <b>pnmtopng</b> to use one type of
row filter. <b>pnmtopng</b> chooses whichever of the permitted
filters it finds to be optimal. If you specify none of these options,
it is the same as specifying all of them -- <b>pnmtopng</b> uses any
row filter type it finds optimal.
<p>These options were new with Netpbm 10.22 (April 2004). Before that,
you could use the <b>-filter</b> option to specify one permitted row
filter type. The default, when you specify no filter options, was the
same.
<DT><B>-compression </b><i>level</i>
<DD> To explicitly set the compression level of zlib use this
parameter. Select a level between 0 for no compression (maximum speed)
and 9 for maximum compression (minimum speed).
<DT><B>-force</B>
<DD>
When you specify this, <b>pnmtopng</b> limits its optimizations.
The resulting PNG output is as similar to the Netpbm input as possible.
For example, the PNG output will not be paletted and the alpha channel
will be represented as a full alpha channel even if the information could
be represented more succinctly with a transparency chunk.
<DT><B>-libversion</B>
<DD>
This option causes <b>pnmtopng</b> to do nothing but display version
information about the libraries it uses.
</DL>
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<H2>SEE ALSO</H2>
<A HREF="pngtopnm.html">pngtopnm</A>,
<A HREF="pnmremap.html">pnmremap</A>,
<A HREF="pnmgamma.html">pnmgamma</A>,
<A HREF="pnm.html">pnm</A>
<p>For information on the PNG format, see <a
href="http://schaik.com/png">http://schaik.com/png</a>.
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<H2>AUTHORS</H2>
Copyright (C) 1995-1997 by Alexander Lehmann and Willem van Schaik.
<HR>
<A NAME="index"> </A>
<H2>Table Of Contents</H2>
<UL>
<LI><A HREF="#lbAB">NAME</A>
<LI><A HREF="#lbAC">SYNOPSIS</A>
<LI><A HREF="#lbAD">DESCRIPTION</A>
<LI><A HREF="#lbAE">OPTIONS</A>
<LI><A HREF="#lbAF">SEE ALSO</A>
<LI><A HREF="#lbAI">AUTHORS</A>
</UL>
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