Ruby extension for the libvips image processing library.
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README.md

ruby-vips

Gem Version Build Status

This gem provides a Ruby binding for the libvips image processing library.

Programs that use ruby-vips don't manipulate images directly, instead they create pipelines of image processing operations building on a source image. When the end of the pipe is connected to a destination, the whole pipeline executes at once, streaming the image in parallel from source to destination a section at a time.

Because ruby-vips is parallel, it's quick, and because it doesn't need to keep entire images in memory, it's light. For example, the benchmark at vips-benchmarks loads a large image, crops, shrinks, sharpens and saves again, and repeats 10 times.

real time in seconds, fastest of five runs
benchmark       tiff    jpeg
ruby-vips.rb	0.85	0.78	
image-magick	2.03	2.44	
rmagick.rb	3.87	3.89	

peak memory use in kb
benchmark	peak RES
ruby-vips.rb	43864
rmagick.rb	788768

See also benchmarks at the official libvips website. There's a handy blog post explaining how libvips opens files which gives some more background.

Requirements

Install

It's just:

$ gem install ruby-vips

or include it in Gemfile:

gem 'ruby-vips'

On Windows, you'll need to set the RUBY_DLL_PATH environment variable to point to the libvips bin directory.

Take a look in examples/. There is full API documentation.

Example

require 'vips'

im = Vips::Image.new_from_file filename

# put im at position (100, 100) in a 3000 x 3000 pixel image, 
# make the other pixels in the image by mirroring im up / down / 
# left / right, see
# https://jcupitt.github.io/libvips/API/current/libvips-conversion.html#vips-embed
im = im.embed 100, 100, 3000, 3000, extend: :mirror

# multiply the green (middle) band by 2, leave the other two alone
im *= [1, 2, 1]

# make an image from an array constant, convolve with it
mask = Vips::Image.new_from_array [
    [-1, -1, -1],
    [-1, 16, -1],
    [-1, -1, -1]], 8
im = im.conv mask, precision: :integer

# finally, write the result back to a file on disk
im.write_to_file output_filename

Older versions

There are two older versions of this gem.

The 0.3-stable branch is written in C and supports a different API. It still works, but is only maintained for compatibility.

The 1.0-stable branch is based on gobject-introspection rather than ffi. It supports the same API as the current version, but is harder to install, less portable, slower, and less stable.