Lua bindings to ImageMagick's MagicWand or GraphicsMagick's Wand for LuaJIT using FFI.
You'll need both LuaJIT (any version) and MagickWand or GraphicsMagickinstalled.
On Ubuntu, to use ImageMagick, you might run:
$ sudo apt-get install luajit
$ sudo apt-get install libmagickwand-dev
You can install GraphicsMagick in place of, or alongside, ImageMagick:
$ sudo apt-get install libgraphicsmagick1-dev
It's recommended to use LuaRocks to install magick.
$ sudo apt-get install luarocks
$ luarocks install magick
If you just need to resize/crop an image, use the thumb
function. It provides
a shorthand syntax for common operations.
local magick = require("magick")
magick.thumb("input.png", "100x100", "output.png")
The second argument to thumb
is a size string, it can have the following
kinds of values:
"500x300" -- Resize image such that the aspect ratio is kept,
-- the width does not exceed 500 and the height does
-- not exceed 300
"500x300!" -- Resize image to 500 by 300, ignoring aspect ratio
"500x" -- Resize width to 500 keep aspect ratio
"x300" -- Resize height to 300 keep aspect ratio
"50%x20%" -- Resize width to 50% and height to 20% of original
"500x300#" -- Resize image to 500 by 300, but crop either top
-- or bottom to keep aspect ratio
"500x300+10+20" -- Crop image to 500 by 300 at position 10,20
If you need more advanced image operations, you'll need to work with the
Image
object. Read on.
All functions contained in the table returned by require("magick")
.
thumb(input_fname, size_str, out_fname=nil)
Loads and resizes image. Write output to out_fname
if provided, otherwise a
string is returned with the binary data of the resulting image.
(input_fname
can optionally be an instance of Image
)
size_str
is a described above under thumb
.
load_image(fname)
Return a new Image
instance, loaded from filename. Returns nil
and error
message if image could not be loaded.
load_image_from_blob(blob)
Loads an image from a Lua string containing the binary image data.
Image
objectCalling load_image
or load_image_from_blob
returns an Image
object.
local magick = require "magick"
local img = assert(magick.load_image("hello.png"))
print("width:", img:get_width(), "height:", img:get_height());
img:resize(200, 200)
img:write("resized.png")
Images are automatically freed from memory by LuaJIT's garbage collector, but
images can take up a lot of space in memory when loaded so it's recommended to
call destroy
on the image object as soon as possible.
ImageMagick and GraphicsMagick implement (mostly) the same interface. By
default the magick
module will include ImageMagick. You can specify which
library you use by calling require
on the module for the appropriate library.
At the moment it's impossible to include both libraries into the same process
due to collision of function names in the C namespace.
Load ImageMagick directly:
magick = requrie "magick.wand"
local img = magick.load_image("some_image.png")
Load GraphicsMagick directly:
magick = requrie "magick.gmwand"
local img = magick.load_image("some_image.png")
Note: Not all the functionality of the respective image libraries is exposted on the Image interface. Pull requests welcome.
Methods mutate the current image when appropriate. Use clone
to get an
independent copy.
img:resize(w,h, f="Lanczos2", blur=1.0)
Resizes the image, f
is resize function, see Filer Types
img:adaptive_resize(w,h)
Resizes the image using adaptive resize
img:crop(w,h, x=0, y=0)
Crops image to w
,h
where the top left is x
, y
img:blur(sigma, radius=0)
Blurs the image with specified parameters. See Blur Arguments
img:rotate(degrees, r=0, g=0, b)
Rotates the image by specified number of degrees. The image dimensions will
enlarge to prevent cropping. The triangles on the corners are filled with the
color specified by r
, g
, b
. The color components are specified as
floating point numbers from 0 to 1.
img:sharpen(sigma, radius=0)
Sharpens the image with specified parameters. See Sharpening Images
img:resize_and_crop(w,h)
Resizes the image to w
,h
. The image will be cropped if necessary to
maintain its aspect ratio.
img:get_blob()
Returns Lua string containing the binary data of the image. The blob is
formatted the same as the image's current format (eg. PNG, Gif, etc.). Use
image:set_format
to change the format.
img:write(fname)
Writes the image to the specified filename
img:get_width()
Gets the width of the image
img:get_height()
Gets the height of the image
img:get_format()
Gets the current format of image as a file extension like "png"
or "bmp"
.
Use image:set_format
to change the format.
img:set_format(format)
Sets the format of the image, takes a file extension like "png"
or "bmp"
img:get_quality()
Gets the image compression quality.
img:set_quality(quality)
Sets the image compression quality.
img:get_gravity()
Gets the image gravity type.
img:set_gravity(gravity)
Sets the image's gravity type:
gravity
can be one of the values listed in data.moon
img:get_option(magick, key)
Returns all the option names that match the specified pattern associated with a
image (e.g img:get_option("webp", "lossless")
)
img:set_option(magick, key, value)
Associates one or options with the img (e.g img:set_option("webp", "lossless", "0")
)
img:scale(w, h)
Scale the size of an image to the given dimensions.
img:coalesce()
Coalesces the current image by compositing each frame on the previous frame. This un-optimized animated images to make them suitable for other methods.
img:composite(source, x, y, compose)
Composite another image onto another at the specified offset x
, y
.
compose
can be one of the values listed in data.moon
img:strip()
Strips image of all profiles and comments, useful for removing exif and other data
r,g,b,a = img:get_pixel(x, y)
Get the r,g,b,a color components of a pixel in the image as doubles from 0
to 1
img:clone()
Returns a copy of the image.
img:modulate(brightness=100, saturation=100, hue=100)
Adjust the brightness, saturation, and hue of the image. See Modulate Brightness, Saturation, and Hue
img:thumb(size_str)
Mutates the image to be a thumbnail. Uses the same size string format described at the top of this README.
img:destroy()
Immediately frees the memory associated with the image, it is invalid to use the image after calling this method. It is unnecessary to call this method normally as images are tracked by the garbage collector.
Tests use Busted. Install and execute the
following command to run tests. You can check the output in
spec/output_images/
.
$ busted
coalesce
for ImageMagicksharpen
, set_quality
, auto_orient
, get_colorspace
, set_colorspace
, level_image
, hald_clut
for GraphicsMagickthumb
, handle case when source size is missing, more specs for thumb
modulate
get_depth
and set_depth
to GraphicsMagick & ImageMagickreset_page
to GraphicsMagickget_format
and set_format
to GraphicsMagickthumb
method on the image classffi.gc
coalesce
, rotate
methods to imagepkg-config
instead of MagickWand-config
to query libraryAuthor: Leaf Corcoran (leafo) (@moonscript)
Email: leafot@gmail.com
Homepage: http://leafo.net