303 lines
7.7 KiB
HTML
303 lines
7.7 KiB
HTML
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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
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<HTML><HEAD><TITLE>Man page of pnmtopng</TITLE>
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</HEAD><BODY>
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<H1>pnmtopng</H1>
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Section: User Commands (1)<BR>Updated: 6 January 1997<BR><A HREF="#index">Index</A>
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<A HREF="/cgi-bin/man/man2html">Return to Main Contents</A><HR>
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<A NAME="ixAAB"></A>
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<A NAME="lbAB"> </A>
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<H2>NAME</H2>
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pnmtopng - convert a portable anymap into a Portable Network Graphics file
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>pnmtopng</B>
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[-verbose]
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[-downscale]
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[-interlace]
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[-alpha file]
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<BR>
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[-transparent [=]color]
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[-background color]
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[-gamma value]
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<BR>
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[-hist]
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[-chroma wx wy rx ry gx gy bx by]
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[-phys x y unit]
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<BR>
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[-text file]
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[-ztxt file]
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[-time [yy]yy-mm-dd hh:mm:ss]
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<BR>
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[-filter type]
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[-compression level]
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[-force]
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[<I>pnmfile</I>]
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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Reads a portable pixmap as input.
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Produces a Portable Network Graphics file as output.
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<A NAME="ixAAC"></A>
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<P>
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Color values in PNG files are either eight or sixteen bits wide, so
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<I>pnmtopng</I>
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will automatically scale colors to have a maxval of 255 or 65535.
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Grayscale files will be produced with bit depths 1, 2, 4, 8 or 16.
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An extra
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<I>pnmdepth</I>
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step is not necessary.
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<A NAME="lbAE"> </A>
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<H2>OPTIONS</H2>
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<DL COMPACT>
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<DT id="1"><B>-verbose</B>
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<DD>
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Display the format of the output file.
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<DT id="2"><B>-downscale</B>
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<DD>
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Enables scaling of maxvalues of more then 65535 to 16 bit. Since this means
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loss of image data, the step is not performed by default.
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<DT id="3"><B>-interlace</B>
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<DD>
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Creates an interlaced PNG file (Adam7).
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<DT id="4"><B>-alpha file</B>
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<DD>
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The alpha channel of pixel (or image) specifies the transparency of a pixel.
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To create this fourth pixel value a separate
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<I>.pbm-</I>
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or
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<I>.pgm-file</I>
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is needed. In this file black (0) stands for fully transparant and white (1)
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will become opaque. The sizes of both pbm/pgm/ppm-files must be the same.
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If the information contained in the alpha mask can also be represented as
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a transparency index, it will be used, since this should result in a smaller
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image file.
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<DT id="5"><B>-transparent color</B>
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<DD>
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<B>ppmtogif</B>
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marks the specified color as transparent in the PNG image.
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<P>
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You specify the color as in
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<B><A HREF="/cgi-bin/man/man2html?1+ppmmake">ppmmake</A></B>(1).<B>E.g.</B>
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<B>red</B>
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or
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<B>rgb:ff/00/0d</B>.
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If the color you specify is not present in the image,
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<B>pnmtopnm</B>
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selects instead the color in the image that is closest to the one you
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specify. Closeness is measured as a cartesian distance between colors
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in RGB space. If multiple colors are equidistant,
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<B>pnmtopnm</B>
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chooses one of them arbitrarily.
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<P>
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However, if you prefix your color specification with "=", e.g.
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<P>
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<B>-transparent =red</B>
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<P>
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Only the exact color you specify will be transparent. If that color does
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not appear in the image, there will be no transparency.
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<B>pnmtopng</B>
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issues an information message when this is the case.
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<P>
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<P>
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<DT id="6"><B>-background color</B>
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<DD>
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To create a background color chunck in the
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<I>png-file,</I>
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which can be used for subsequent alpha-channel or transparent-color
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conversions. See -transparent for format of color.
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<DT id="7"><B>-gamma value</B>
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<DD>
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Creates an gAMA chunk. By providing the gamma-value of the
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<I>pnm-file</I>
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the software that lateron will display the
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<I>png-file</I>
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will be able to do the necessary gamma-corrections. A good rule-of-thumb is
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that when the file is created by a software program (like a CAD-program or
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a ray-tracer) the value is probably 1.0. When the
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<I>pnm-file</I>
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looks good on a non-gamma corrected PC display (which has itself a gamma-value
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of 2.2 - 2.8), a value of 0.45 should be given.
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<DT id="8"><B>-hist</B>
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<DD>
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Use this parameter to create a chunk that specifies the frequency (or histogram)
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of the colors in the image.
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<DT id="9"><B>-chroma white point X and Y, red X and Y, green X and Y, and blue X and Y</B>
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<DD>
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To specify the white point and rgb values following the CIE-1931 spec.
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<DT id="10"><B>-phys x y unit</B>
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<DD>
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When your image should not be displayed with square but with rectangular
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pixels this option should be used to create a pHYS chunk. When the unit-value
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is 0 the x and y only gives the ratio of pixel width and height. When it is
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1 the x and y specify the number of pixels per meter.
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<DT id="11"><B>-text file</B>
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<DD>
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Allows to include comments in the text-chunk of the
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<I>png-file.</I>
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The format of the text-file is as follows: when the first column does not
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contain a blank or a tab, the first word is considered to be the keyword.
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For keywords to contain spaces, enclose them in double-quotes.
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<BR>
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When the first character on a line is a blank or tab, the rest of the line
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is a new line of the current comment.
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Note that the initial spaces are not considered to be part of the comment
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line.
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<BR>
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<P>
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<BR>
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Here is an example:
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<BR>
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-------------------------------------------
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<BR>
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Title PNG-file
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<BR>
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Author your name
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<BR>
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Description how to include a text-chunk
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<BR> into a PNG file
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<BR>
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"Creation date" 3-feb-1987
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<BR>
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Software pnmtopng
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<BR>
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-------------------------------------------
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<DT id="12"><B>-ztxt file</B>
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<DD>
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The same as -text, but now the text will be compressed.
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<DT id="13"><B>-time yy-mm-dd hh:mm:ss or -time yyyy-mm-dd hh:mm:ss</B>
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<DD>
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This option allows you to specify the (modification)time. The year parameter
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can be given as a two- or a four-digit value.
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<DT id="14"><B>-filter type</B>
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<DD>
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When the types of filters must be restricted you can specify here
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which filter you want to use. Allowed values are: 0 (none), 1 (sub),
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2 (up), 3 (avg) and 4 (paeth).
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<DT id="15"><B>-compression level</B>
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<DD>
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To explicitly set the compression level of zlib use this parameter. Select
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a level between 0 for no compression (max speed) and 9 for maximum compression.
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<DT id="16"><B>-force</B>
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<DD>
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When set, -force limits the optimizations of pnmtopng. A png-file similar
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to the pnm-input is as much as possible enforced. For example no paletted
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files will be created and alpha-channel images will not be converted to
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images with a transparency chunck.
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</DL>
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<P>
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All flags can be abbreviated to their shortest unique prefix.
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<A NAME="lbAF"> </A>
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<H2>SEE ALSO</H2>
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<A HREF="/cgi-bin/man/man2html?1+pngtopnm">pngtopnm</A>(1), <A HREF="/cgi-bin/man/man2html?1+gif2png">gif2png</A>(1), <A HREF="/cgi-bin/man/man2html?1+pnmgamma">pnmgamma</A>(1), <A HREF="/cgi-bin/man/man2html?5+pnm">pnm</A>(5)
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<A NAME="lbAG"> </A>
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<H2>NOTE</H2>
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Instead of xxxtopnm|pnmtopng, a specific converter should be used, if
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available.
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E.g.
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<I>gif2png</I>
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(GIF conversion), etc.
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<A NAME="lbAH"> </A>
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<H2>BUGS</H2>
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There could be an option to read the comment text from pnm comments instead
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of a separate file.
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<P>
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The program could be much faster, with a bit of code optimizing.
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<A NAME="lbAI"> </A>
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<H2>AUTHORS</H2>
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Copyright (C) 1995-1997 by Alexander Lehmann
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<BR>
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<BR> and Willem van Schaik.
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<P>
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<HR>
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<A NAME="index"> </A><H2>Index</H2>
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<DL>
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<DT id="17"><A HREF="#lbAB">NAME</A><DD>
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<DT id="18"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="19"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="20"><A HREF="#lbAE">OPTIONS</A><DD>
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<DT id="21"><A HREF="#lbAF">SEE ALSO</A><DD>
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<DT id="22"><A HREF="#lbAG">NOTE</A><DD>
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<DT id="23"><A HREF="#lbAH">BUGS</A><DD>
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<DT id="24"><A HREF="#lbAI">AUTHORS</A><DD>
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</DL>
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<HR>
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This document was created by
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<A HREF="/cgi-bin/man/man2html">man2html</A>,
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using the manual pages.<BR>
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Time: 00:05:24 GMT, March 31, 2021
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</BODY>
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</HTML>
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