A ruby wrapper for ImageMagick or GraphicsMagick command line.
I was using RMagick and loving it, but it was eating up huge amounts of memory. Even a simple script would use over 100MB of RAM. On my local machine this wasn't a problem, but on my hosting server the ruby apps would crash because of their 100MB memory limit.
Using MiniMagick the ruby processes memory remains small (it spawns ImageMagick's command line program mogrify which takes up some memory as well, but is much smaller compared to RMagick). See Thinking of switching from RMagick? below.
MiniMagick gives you access to all the command line options ImageMagick has (found here).
ImageMagick or GraphicsMagick command-line tool has to be installed. You can check if you have it installed by running
$ convert -version
Version: ImageMagick 6.8.9-7 Q16 x86_64 2014-09-11 http://www.imagemagick.org
Copyright: Copyright (C) 1999-2014 ImageMagick Studio LLC
Features: DPC Modules
Delegates: bzlib fftw freetype jng jpeg lcms ltdl lzma png tiff xml zlib
MiniMagick has been tested on following Rubies:
- MRI 1.9.2
- MRI 1.9.3
- MRI 2.0.0
- MRI 2.1.x
- Rubinius
The latest version (4.0.0) doesn't work on JRuby (because of a bug in JRuby), so if you need JRuby support, use the 3.x versions.
Add the gem to your Gemfile:
gem "mini_magick"
Let's first see a basic example of resizing an image.
image = MiniMagick::Image.open("input.jpg")
image.path #=> "/var/folders/k7/6zx6dx6x7ys3rv3srh0nyfj00000gn/T/magick20140921-75881-1yho3zc.jpg"
image.resize "100x100"
image.format "png"
image.write "output.png"
MiniMagick::Image.open
makes a copy of the image, and further methods modify
that copy (the original stays untouched). We then
resize
the image, and write it to a file. The writing part is necessary because
the copy is just temporary, it gets garbage collected when we lose reference
to the image.
MiniMagick::Image.open
also accepts URLs.
image = MiniMagick::Image.open("http://example.com/image.jpg")
image.contrast
image.write("from_internets.jpg")
On the other hand, if we want the original image to actually get modified,
we can use MiniMagick::Image.new
.
image = MiniMagick::Image.new("input.jpg")
image.path #=> "input.jpg"
image.resize "100x100"
# No calling #write, because it's no a copy
While using methods like #resize
directly is convenient, if we use more
methods in this way, it quickly becomes inefficient, because it calls the
command on each methods call. MiniMagick::Image#combine_options
takes
multiple options and from them builds one single command.
image.combine_options do |b|
b.resize "250x200>"
b.rotate "-90"
b.flip
end # the command gets executed
As a handy shortcut, MiniMagick::Image.new
also accepts an optional block
which is used to combine_options
.
image = MiniMagick::Image.new("input.jpg") do |b|
b.resize "250x200>"
b.rotate "-90"
b.flip
end # the command gets executed
A MiniMagick::Image
has various handy attributes.
image.type #=> "JPEG"
image.mime_type #=> "image/jpeg"
image.width #=> 250
image.height #=> 300
image.dimensions #=> [250, 300]
image.size #=> 3451 (in bytes)
image.colorspace #=> "DirectClass sRGB"
image.exif #=> {"DateTimeOriginal" => "2013:09:04 08:03:39", ...}
image.resolution #=> [75, 75]
image.signature #=> "60a7848c4ca6e36b8e2c5dea632ecdc29e9637791d2c59ebf7a54c0c6a74ef7e"
If you need more control, and want to access raw image
attributes, you can use #[]
.
image["%[gamma]"] # "0.9"
MiniMagick.configure do |config|
config.cli = :graphicsmagick
config.timeout = 5
end
For a complete list of configuration options, see Configuration.
MiniMagick also alows you to composite images:
first_image = MiniMagick::Image.new("first.jpg")
second_image = MiniMagick::Image.new("second.jpg")
result = first_image.composite(second_image) do |c|
c.compose "Over" # OverCompositeOp
c.geometry "+20+20" # copy second_image onto first_image from (20, 20)
end
result.write "output.jpg"
For multilayered images you can access its layers.
gif.frames #=> [...]
pdf.pages #=> [...]
psd.layers #=> [...]
gif.frames.each_with_index do |frame, idx|
frame.write("frame#{idx}.jpg")
end
By default, MiniMagick validates images each time it's opening them. It
validates them by running identify
on them, and see if ImageMagick finds
them valid. This adds slight overhead to the whole processing. Sometimes it's
safe to assume that all input and output images are valid by default and turn
off validation:
MiniMagick.configure do |config|
config.validate_on_create = false
config.validate_on_write = false
end
You can test whether an image is valid:
image.valid?
image.validate! # raises MiniMagick::Invalid if image is invalid
When things go wrong and commands start failing, you can set the debug mode:
MiniMagick.configure do |config|
config.debug = true
end
In this mode every command that gets executed in the shell will be written to stdout.
Default CLI is ImageMagick, but if you want to use GraphicsMagick, you can specify it in configuration:
MiniMagick.configure do |config|
config.cli = :graphicsmagick
end
If you're a real ImageMagick guru, you might want to use GraphicsMagick only
for certain processing blocks (because it's more efficient), or vice versa. You
can acomplish this with .with_cli
:
MiniMagick.with_cli(:graphicsmagick) do
# Some processing that GraphicsMagick is better at
end
If you want to be close to the metal, you can use ImageMagick's command-line tools directly.
MiniMagick::Tool::Mogrify.new do |mogrify|
mogrify.resize "100x100"
mogrify.antialias.+
mogrify << "image.jpg"
end
# executes `mogrify -resize 100x100 +antialias image.jpg`
I would highly recommend this if you want to maximize performance of your image processing.
See MiniMagick::Tool.
This gem raises an error when ImageMagick returns a nonzero exit code.
Sometimes, however, ImageMagick returns nonzero exit codes when the command
actually went ok. In these cases, to avoid raising errors, you can pass false
to MiniMagick::Tool
's constructor.
MiniMagick::Tool::Identify.new(false) do |b|
b.help
end
Unlike RMagick, MiniMagick is a much thinner wrapper around ImageMagick.
- To piece together MiniMagick commands refer to the Mogrify
Documentation. For instance
you can use the
-flop
option asimage.flop
. - Operations on a MiniMagick image tend to happen in-place as
image.trim
, whereas RMagick has both copying and in-place methods likeimage.trim
andimage.trim!
. - To open files with MiniMagick you use
MiniMagick::Image.open
as you wouldMagick::Image.read
. To open a file and directly edit it, useMiniMagick::Image.new
.