216 lines
5.7 KiB
HTML
216 lines
5.7 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 pnmcomp</TITLE>
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</HEAD><BODY>
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<H1>pnmcomp</H1>
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Section: User Commands (1)<BR>Updated: 12 April 2000<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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pnmcomp - composite (overlay) two portable anymap files together
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<A NAME="lbAC"> </A>
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<H2>SYNOPSIS</H2>
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<B>pnmcomp</B>
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[<B>-xoff=</B><I>X</I> | <B>-align=</B>{<B>left</B>,<B>center</B>,<B>right</B>}]
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<BR>
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[<B>-yoff=</B><I>Y</I> | <B>-valign=</B>{<B>top</B>,<B>middle</B>,<B>bottom</B>}]
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<BR>
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[<B>-alpha=</B><I>alpha-pgmfile</I>]
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[<B>-invert</B>]
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<BR>
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<I>overlay</I>
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[<I>pnm-input</I>]
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[<I>pnm-output</I>]
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<P>
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Minimum unique abbreviations are acceptable.
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<P>
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<A NAME="lbAD"> </A>
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<H2>DESCRIPTION</H2>
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<B>pnmcomp</B>
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reads two images and produces a composite image with one of the images
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overlayed on top of the other. The images need not be the same size.
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The input and outputs are PNM format image files.
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<P>
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In its simplest use,
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<B>pnmcomp</B>
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simply places the
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<I>overlay</I>
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file on top of the
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<I>pnm-input</I>
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file, blocking out the part of the
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<I>pnm-input</I>
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file beneath it.
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If you specify the
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<I>alpha-pgmfile</I>,
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<B>pnmcomp</B>
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uses it as an alpha mask, which means it determines the level of
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transparency of each point in the overlay image. The alpha mask must
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have the same dimensions as the overlay image. In places where the
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alpha mask defines the overlay image to be opaque, the composite
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output contains only the contents of the overlay image; the underlying
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image is totally blocked out. In places where the alpha mask defines
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the overlay image to be transparent, the composite output contains
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none of the overlay image; the underlying image shows through
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completely. In places where the alpha mask shows a value in between
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opaque and transparent (translucence), the composite image contains a
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mixture of the overlay image and the underlying image and the level of
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translucence determines how much of each.
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<P>
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The alpha mask is a PGM file in which a white pixel represents opaqueness
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and a black pixel transparency. Anything in between is translucent.
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<P>
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In some image file formats (PNG, for example), transparency
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information (the alpha mask) is part of the definition of the image.
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In the PNM formats, transparency is always embodied in a separate
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companion file. The PNM converter programs that convert from an image
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format such as PNG have options that allow you to extract the
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transparency information to a separate file, which you can then use
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as input to
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<B>pnmcomp</B>.
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<P>
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The output image is always of the same dimensions as the underlying image.
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<B>pnmcomp</B>
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only uses parts of the overlay image that fit within the underlying
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image.
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<P>
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To specify where on the underlying image to place the overlay image,
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use the
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<B>-xoff</B>,
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<B>-yoff</B>,
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<B>-align</B>,
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and
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<B>-valign</B>
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options. Without these options, the default horizontal position is
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flush left and the default vertical position is flush top.
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<P>
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The overlay and underlying images may be of different formats (e.g.
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overlaying a PBM text image over a full color PPM image) and have different
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maxvals. The output image has the more general of the two input formats
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and a maxval that is the least common multiple the two maxvals (or the
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maximum maxval allowable by the format, if the LCM is more than that).
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<P>
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<P>
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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>-invert</B>
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<DD>
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This option inverts the sense of the values in the alpha mask, which
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effectively switches the roles of the overlay image and the underlying
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image in places where the two intersect.
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<DT id="2"><B>-xoff </B><I>X</I>
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<DD>
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<DT id="3"><B>-yoff </B><I>Y</I>
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<DD>
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These options position the overlay image with respect to the underlying
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image.
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<I>X</I>
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and
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<I>Y</I>
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are the horizontal and vertical displacements of the top left corner of
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the overlay image from the top left corner of the underlying image, in
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pixels. A positive value means right or down; a negative value means
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left or up. The overlay need not fit entirely (or at all) on the
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underlying image.
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<B>pnmcomp</B>
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uses only the parts that lie over the underlying image.
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<DT id="4"><B>-align=</B>[<B>left</B>,<B>center</B>,<B>right</B>]
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<DD>
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This option is an alternative to
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<B>-xoff</B>,
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in the style of HTML. It selects the horizontal position of the overlay
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image so that it is flush left, centered, or flush right on the underlying
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image.
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<DT id="5"><B>-valign=</B>[<B>top</B>,<B>middle</B>,<B>bottom</B>]
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<DD>
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This option is an alternative to
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<B>-yoff</B>,
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in the style of HTML. It selects the vertical position of the overlay
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image so that it is flush top, centered, or flush bottom on the underlying
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image.
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<P>
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</DL>
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<A NAME="lbAF"> </A>
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<H2>SEE ALSO</H2>
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<B><A HREF="/cgi-bin/man/man2html?1+ppmmix">ppmmix</A></B>(1)
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and
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<B><A HREF="/cgi-bin/man/man2html?1+pnmpaste">pnmpaste</A></B>(1)
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are simpler, less general versions of the same tool.
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<P>
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<B><A HREF="/cgi-bin/man/man2html?5+pnm">pnm</A></B>(5),
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<B><A HREF="/cgi-bin/man/man2html?1+pbmmask">pbmmask</A></B>(1)
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<A NAME="lbAG"> </A>
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<H2>AUTHOR</H2>
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Copyright (C) 1992 by David Koblas (<A HREF="mailto:koblas@mips.com">koblas@mips.com</A>).
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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="6"><A HREF="#lbAB">NAME</A><DD>
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<DT id="7"><A HREF="#lbAC">SYNOPSIS</A><DD>
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<DT id="8"><A HREF="#lbAD">DESCRIPTION</A><DD>
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<DT id="9"><A HREF="#lbAE">OPTIONS</A><DD>
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<DT id="10"><A HREF="#lbAF">SEE ALSO</A><DD>
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<DT id="11"><A HREF="#lbAG">AUTHOR</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: 00:05:23 GMT, March 31, 2021
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</BODY>
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</HTML>
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