PNM - A Ruby library for PNM image files (PBM, PGM, PPM)

PNM is a pure Ruby library for creating, reading, and writing of PNM image files (Portable Anymap):

PBM (Portable Bitmap),
PGM (Portable Graymap), and
PPM (Portable Pixmap).

Examples

Create a PGM grayscale image from a two-dimensional array of gray values:

require 'pnm'

# pixel data
pixels = [[ 0, 10, 20],
          [10, 20, 30]]

# optional settings
options = {:maxgray => 30, :comment => 'Test Image'}

# create the image object
image = PNM::Image.new(pixels, options)

# retrieve some image properties
image.info    # => "PGM 3x2 Grayscale"
image.width   # => 3
image.height  # => 2

See PNM::Image.new for a more detailed description of pixel data formats and available options.

Write an image to a file:

image.write('test.pgm')

# use ASCII or "plain" format (default is binary)
image.write('test.pgm', :ascii)

# write to an I/O stream
File.open('test.pgm', 'w') {|f| image.write(f) }

Read an image from a file (returns a PNM::Image object):

image = PNM.read('test.pgm')
image.comment  # => "Test Image"
image.maxgray  # => 30
image.pixels   # => [[0, 10, 20], [10, 20, 30]]

Force an image type:

image = PNM::Image.new([[0, 1],[1, 0]], :type => :ppm)
image.info  # => "PPM 2x2 Color"

Installation

To install PNM, you can either

use gem install pnm to install from RubyGems.org,
clone or download the repository and use rake build and [sudo] gem install pnm.

Requirements

No additional Ruby gems or native libraries are needed.
PNM has been tested with
- Ruby 2.0.0 on Linux and on Windows,
- Ruby 1.9.3,
- JRuby 1.7.8,
- Rubinius 2.2.1.

Documentation

Documentation should be available via ri PNM.

Reporting bugs

Report bugs on the PNM home page: https://github.com/stomar/pnm/

License

PNM is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License version 3 or later (GPLv3+), see www.gnu.org/licenses/gpl.html. There is NO WARRANTY, to the extent permitted by law.