\
.\" This man page was generated by the Netpbm tool 'makeman' from HTML source.
.\" Do not hand-hack it!  If you have bug fixes or improvements, please find
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.TH "Pnmtoddif User Manual" 0 "27 May 2026" "netpbm documentation"

.SH NAME

pnmtoddif - Convert a PNM image to DDIF format

.UN synopsis
.SH SYNOPSIS

\fBpnmtoddif\fP
[\fB-resolution\fP \fIx\fP \fIy\fP]
[\fIpnmfile\fP [\fIddiffile\fP]]

.UN description
.SH DESCRIPTION
.PP
This program is part of
.BR "Netpbm" (1)\c
\&.
.PP
\fBpnmtoddif\fP takes a PNM image and converts it into a DDIF image
file.
.PP
\fBpnmtoddif\fP writes PBM format (bitmap) data as a 1 bit DDIF,
PGM format data (grayscale) as an 8 bit grayscale DDIF, and PPM format
(color) data as an 8,8,8 bit color DDIF.  \fBpnmtoddif\fP writes any
DDIF image file uncompressed.  The data plane organization is
interleaved by pixel.
.PP
In addition to the number of pixels in the width and height
dimension, DDIF images also carry information about the size that the
image should have, that is, the physical space that a pixel occupies.
Netpbm images do not carry this information, hence you have to supply
it externally.  The default of 75 dpi has the beneficial property of
not causing a resize on most Digital Equipment Corporation color
monitors.

(Until 2026, this manual said the default was 78 dpi, but it has always been
implemented as 75, which is a typical resolution value.  We include this note
in case 78 is actually more sensible and the program has just been defective
all this time).
.PP
\fIThis program works only on Netpbm input images with maxval 255.  For
other images, it produces incorrect results.\fP  If you have a Netpbm image
with maxval other than 255, use \fBpamdepth\fP to change it to 255 for use
with this program.
  
.UN options
.SH OPTIONS
.PP
In addition to the options common to all programs based on libnetpbm
(most notably \fB-quiet\fP, see 
.UR index.html#commonoptions
 Common Options
.UE
\&), \fBpnmtoddif\fP recognizes the following
command line option:


.TP
\fB-resolution\fP \fIx\fP \fIy\fP
The horizontal and vertical resolution of the output image in dots
per inch.  Default is 75 dpi.



.UN arguments
.SH ARGUMENTS


.TP
\fIpnmfile\fP
The filename for the image file in pnm format.  Default is to
read from Standard Input.

.TP
\fIddiffile\fP
The filename for the image file to be created in DDIF format.  By
default, \fBpnmtoddif\fP writes to Standard Output.



.UN seealso
.SH SEE ALSO
.BR "pnm" (1)\c
\&

.UN author
.SH AUTHOR

Burkhard Neidecker-Lutz, Digital Equipment Corporation, CEC Karlsruhe
\fIneideck@nestvx.enet.dec.com\fP
.SH DOCUMENT SOURCE
This manual page was generated by the Netpbm tool 'makeman' from HTML
source.  The master documentation is at
.IP
.B http://netpbm.sourceforge.net/doc/pnmtoddif.html
.PP