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pnmtotiff(1) General Commands Manual pnmtotiff(1)

NAME
pnmtotiff - convert a portable anymap into a TIFF file

Minimum unambiguous abbreviations of options are acceptable.

DESCRIPTION
Reads a PNM image as input. Produces a TIFF file as output.

The output goes to Standard Output, which must be a seekable file. That means no pipes, but
any regular file should work.

OPTIONS
By default, pnmtotiff creates a TIFF file with no compression. This is your best bet most of
the time. If you want to try another compression scheme or tweak some of the other even more
obscure output options, there are a number of flags to play with.

Actually, the best default would be to use LZW compression, which is what pnmtotiff used to
do by default. However, the Tiff library no longer does LZW compression due to concerns with
violating Unisys's patent on LZW compression.

The -none, -packbits, -lzw, -g3, -g4, -flate, and -adobeflat options are used to override the
default and set the compression scheme used in creating the output file. The CCITT Group 3
and Group 4 compression algorithms can only be used with bilevel data. -lzw doesn't really
work because the Tiff library doesn't do LZW compression. It used to, but its developers re‐
moved the function out of concern about violating Unisys's patent. This option remains in
case you use a Tiff library that cooperates, now or in the future. The -2d and -fill options
are meaningful only with Group 3 compression: -2d requests 2-dimensional encoding, while
-fill requests that each encoded scanline be zero-filled to a byte boundry. The -predictor
option is only meaningful with LZW compression: a predictor value of 2 causes each scanline
of the output image to undergo horizontal differencing before it is encoded; a value of 1
forces each scanline to be encoded without differencing.

By default, pnmtotiff creates a TIFF file with msb-to-lsb fill order. The -msb2lsb and
-lsb2msb options are used to override the default and set the fill order used in creating the
file.

The fill order is the order in which pixels are packed into a byte in the Tiff raster, in the
case that there are multiple pixels per byte. msb-to-lsb means that the leftmost columns go
into the most significant bits of the byte in the Tiff image. However, there is considerable
confusion about the meaning of fill order. Some believe it means whether 16 bit sample val‐
ues in the Tiff image are little-endian or big-endian. This is totally erroneous (The endi‐
anness of integers in a Tiff image is designated by the image's magic number). However,
ImageMagick and older Netpbm both have been known to implement that interpretation.
2001.09.06.

If the image does not have sub-byte pixels, these options have no effect other than to set
the value of the FILLORDER tag in the Tiff image (which may be useful for those programs that
misinterpret the tag with reference to 16 bit samples).

The -rowsperstrip option can be used to set the number of rows (scanlines) in each strip of
data in the output file. By default, the output file has the number of rows per strip set to
a value that will ensure each strip is no more than 8 kilobytes long.

The -minisblack and -miniswhite option force the output image to have a "minimum is black" or
"minimum is white" photometric, respectively. If you don't specify either, pnmtotiff uses
minimum is black except when using Group 3 or Group 4 compression, in which case pnmtotiff
follows CCITT fax standards and uses "minimum is white." This usually results in better com‐
pression and is generally preferred for bilevel coding.

Before February 2001, pnmtotiff always produced "minimum is black," due to a bug. In either
case, pnmtotiff sets the photometric interpretation tag in the TIFF output according to which
photometric is actually used.

-truecolor tells pnmtotiff to produce the 24-bit RGB form of TIFF output if it is producing a
color TIFF image. Without this option, pnmtotiff produces a colormapped (paletted) 8-bit
TIFF image unless there are more than 256 colors (and in the latter case, issues a warning).

The -truecolor option can prevent pnmtotiff from making two passes through the input file,
thus improving speed and memory usage. See the section MULTIPLE PASSES.

If pnmtotiff produces a grayscale TIFF image, this option has no effect.

-color tells pnmtotiff to produce a color, as opposed to grayscale, TIFF image if the input
is PPM, even if it contains only shades of gray. Without this option, pnmtotiff produces a
grayscale TIFF image if the input is PPM and contains only shades of gray, and at most 256
shades. Otherwise, it produces a color TIFF output. For PBM and PGM input, pnmtotiff always
produces grayscale TIFF output and this option has no effect.

The -color option can prevent pnmtotiff from making two passes through the input file, thus
improving speed and memory usage. See the section MULTIPLE PASSES.

The -indexbits option is meaningful only for a colormapped (paletted) image. In this kind of
image, the raster contains values which are indexes into a table of colors, with the indexes
normally taking less space that the color description in the table. pnmtotiff can generate
indexes of 1, 2, 4, or 8 bits. By default, it will use 8, because many programs that inter‐
pret TIFF images can't handle any other width.

NOTES
There are myriad variations of the TIFF format, and this program generates only a few of
them. pnmtotiff creates a grayscale TIFF file if its input is a PBM (monochrome) or PGM
(grayscale) file. pnmtotiff also creates a grayscale file if it input is PPM (color), but
there is only one color in the image. If the input is a PPM (color) file and there are 256
colors or fewer, but more than 1, pnmtotiff generates a color palette TIFF file. If there
are more colors than that, pnmtotiff generates an RGB (not RGBA) single plane TIFF file. Use
pnmtotiffcmyk to generate the cyan-magenta-yellow-black ink color separation TIFF format.

The number of bits per sample in the TIFF output is determined by the maxval of the PNM in‐
put. If the maxval is less than 256, the bits per sample in the output is the smallest num‐
ber that can encode the maxval. If the maxval is greater than or equal to 256, there are 16
bits per sample in the output.

Multiple Passes
pnmtotiff reads the input image once if it can, and otherwise twice. It needs that second
pass to analyze the colors in the image and generate a color map (pallette) and determine if
the image is grayscale. So the second pass only happens when the input is PPM. And you can
avoid it then by specifying both the -truecolor and -color options.

If the input image is small enough to fit in your system's file cache, the second pass is
very fast. If not, it requires reading from disk twice, which can be slow.

When the input is from a file that cannot be rewound and reread, pnmtotiff reads the entire
input image into a temporary file which can, and works from that. Even if it only needs one
pass.

SEE ALSO
tifftopnm(1), pnmtotiffcmyk(1), pnmdepth(1), pnm(5)

AUTHOR
Derived by Jef Poskanzer from ras2tiff.c, which is Copyright (c) 1990 by Sun Microsystems,
Inc. Author: Patrick J. Naughton (naughton AT wind.com).

24 January 2001 pnmtotiff(1)