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⚡ TLDR: pnmtorle (tldr-pages)

Convert a PNM file to an Utah Raster Tools RLE image file.

Convert a PNM image to an RLE image
pnmtorle {{path/to/input.pnm}} > {{path/to/output.rle}}
Print PNM header information to `stdout`
pnmtorle {{-verb|-verbose}} {{path/to/input.pnm}} > {{path/to/output.rle}}
Include a transparency channel in the output image in which every black pixel is set to fully transparent and every other pixel is set to fully opaque
pnmtorle {{-a|-alpha}} {{path/to/input.pnm}} > {{path/to/output.rle}}

PNMTORLE(1) General Commands Manual PNMTORLE(1)

NAME
pnmtorle - convert a Netpbm image file into an RLE image file.

SYNOPSIS
pnmtorle [ -h ] [ -v ] [ -a ] [ -o outfile ] [ pnmfile ]

DESCRIPTION
This program converts Netpbm image files into Utah RLE(5) image files. You can include an
alpha mask. If the input is a multiple image file, the output consists of several concate‐
nated RLE images.

The RLE file will contain either a three channel color image (24 bits) or a single channel
grayscale image (8 bits) depending upon the pnm file depth. If a converted ppm is displayed
on an 8 bit display, the image must be dithered. In order to produce a better looking image
(on 8 bit displays), it is recommended that the image be quantizing (to 8 bit mapped color)
prior to its display. This may be done by piping the output of this program into the Utah
mcut(1) or rlequant(1) utilities. An example of this is shown later.

OPTIONS
-v This option will cause pnmtorle to operate in verbose mode. The header information is
written to "stderr". Actually, there is not much header information stored in a
Netpbm file, so this information is minimal.

-h This option allows the header of the Netpbm image to be dumped to "stderr" without
converting the file. It is equivalent to using the -v option except that no file con‐
version takes place.

-a This option causes pnmtorle to include an alpha channel in the output image. The al‐
pha channel is based on the image: Wherever a pixel is black, the corresponding alpha
value is transparent. Everywhere else, the alpha value is fully opaque.

-o outfile
If specified, the output will be written to this file. If outfile is "-", or if it is
not specified, the output will be written to the standard output stream.

pnmfile
The name of the Netpbm image data file to be converted. If not specified, standard
input is assumed.

EXAMPLES
pnmtorle -v file.ppm -o file.rle
While running in verbose mode, convert file.ppm to RLE format and store resulting data
in file.rle.

pnmtorle -h file.pgm
Dump the header information of the Netpbm file called file.pgm.