ruby-vips

This gem is 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.

Requirements

macOS, Linux, and Windows tested
libvips 8.2 or later, see the libvips install instructions
ruby-ffi 1.9 or later
Ruby 2.0+, JRuby should work

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.

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://libvips.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

The Vips section in the API docs has a tutorial introduction with examples.

ruby-vips has API documentation. The libvips reference manual has a complete explanation of every method.

The example/ directory has some simple example programs.

Benchmarks

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