EASY IMAGE PROCESSING IN R USING THE MAGICK PACKAGE
This article describes how to perform image processing in R using the magick R package, which is binded to ImageMagick
library: the most comprehensive open-source image processing library available.
The magick R package supports:
- Many common formats: png, jpeg, tiff, pdf, etc
- Different manipulations types: rotate, scale, crop, trim, flip, blur, etc.
All operations are vectorized using the Magick++ STL
meaning they operate either on a single frame or a series of frames for working with layers, collages, or animation.
In RStudio images are automatically previewed when printed to the console, resulting in an interactive editing environment.
Contents:
- Installation
- Load the package
- Formats supported by ImageMagick on your system
- Image editing: Read, Write and Convert images
- Image transformations
- Cut and edit
- Text annotations
- Layers
- Stack layers on top of each other
- Combining or appending images
- Create GIF animation
- Read more
Installation
- For Mac OS or Windowns:
install.packages("magick")
- For Linux, you can install from source
- Install system requirements:
sudo apt-get install -y libmagick++-dev
- Install the R package
install.packages("magick")
Load the package
library(magick)
Formats supported by ImageMagick on your system
str(magick::magick_config())
## List of 21
## $ version :Class 'numeric_version' hidden list of 1
## ..$ : int [1:4] 6 9 6 6
## $ modules : logi FALSE
## $ cairo : logi TRUE
## $ fontconfig : logi TRUE
## $ freetype : logi TRUE
## $ fftw : logi FALSE
## $ ghostscript : logi FALSE
## $ jpeg : logi TRUE
## $ lcms : logi FALSE
## $ libopenjp2 : logi FALSE
## $ lzma : logi TRUE
## $ pangocairo : logi TRUE
## $ pango : logi TRUE
## $ png : logi TRUE
## $ rsvg : logi TRUE
## $ tiff : logi TRUE
## $ webp : logi TRUE
## $ wmf : logi FALSE
## $ x11 : logi FALSE
## $ xml : logi TRUE
## $ zero-configuration: logi TRUE
Image editing: Read, Write and Convert images
Key R functions:
image_read(path, density = NULL, depth = NULL, strip = FALSE)
image_write(image, path = NULL, format = NULL, quality = NULL,
depth = NULL, density = NULL, comment = NULL, flatten = FALSE)
image_convert(image, format = NULL, type = NULL, colorspace = NULL,
depth = NULL, antialias = NULL)
The input image file format can be a file path, URL, or raw vector with image data.
Read an image into R.
frink <- image_read("https://jeroen.github.io/images/frink.png")
## print(frink)
# Shows some meta data about the image
image_info(frink)
## format width height colorspace matte filesize
## 1 PNG 220 445 sRGB TRUE 73494
Export an image in any format to a file on disk. You can specify the format
parameter to convert the image to another format.
# Render png to jpeg
image_write(frink, path = "frink.jpg", format = "jpeg", quality = 75)
If path
is a filename, image_write
returns path
on success such that the result can be piped into function taking a file path.
Convert image formats. You can internally convert the image to another format earlier, before applying transformations. This can be useful if your original format is lossy.
frink_jpeg <- image_convert(frink, "jpeg")
image_info(frink_jpeg)
## format width height colorspace matte filesize
## 1 JPEG 220 445 sRGB TRUE 0
Note that size is currently 0 because ImageMagick is lazy (in the good sense) and does not render until it has to.
Image preview.
- Magick images are automatically displayed in RStudio viewer
- You can also use
image_browse()
to open the image in your system’s default application for a given type. - On Linux you can use
image_display()
to preview the image in an X11 window.
Image transformations
Cut and edit
Several of the transformation functions take an geometry
parameter which requires a special syntax of the form AxB+C+D
where each element is optional. Some examples:
image_trim(image)
: Trims margin.image_crop(image, geometry = "100x150+50")
: crop outwidth:100px
andheight:150px
starting+50px
from the leftimage_scale(image, geometry = "200")
: resize proportionally to width:200px
image_scale(image, grometry = "x200")
: resize proportionally to height:200px
image_fill(image, color = "blue", point = "+100+200")
: flood fill with blue starting at the point atx:100, y:200
image_border(frink, color = "red", geometry = "20x10")
: adds a border of 20px left+right and 10px top+bottom
Change image border and background:
# Add 20px left/right and 10px top/bottom
image_border(image_background(frink, "hotpink"), "#000080", "20x10")
Trim margins:
image_trim(frink)
Crop the image. Options are here width:100px
and height:150px
starting +50px
from the left
image_crop(frink, "100x150+50")
Resize the image:
# Width: 300px
image_scale(frink, "300")
# Height: 300px
image_scale(frink, "x300")
Rotate or mirror the image
image_rotate(frink, 45)
image_flip(frink)
image_flop(frink)
Modulate and paint an image:
# Change the brightness, the saturation and the Hue
image_modulate(frink, brightness = 80, saturation = 120, hue = 90)
# Paint the shirt in blue
image_fill(frink, "blue", point = "+100+200", fuzz = 20)
With image_fill
we can flood fill starting at pixel point
. The fuzz
parameter allows for the fill to cross for adjacent pixels with similarish colors. Its value must be between 0 and 256^2 specifying the max geometric distance between colors to be considered equal. Here we give professor frink a blue shirt.
Text annotations
# Add some text
image_annotate(
frink, text = "I like R!", size = 70, color = "green",
gravity = "southwest"
)
# Customize text
image_annotate(
frink, text = "CONFIDENTIAL", size = 30,
color = "red", boxcolor = "pink",
degrees = 60, location = "+50+100",
font = "Times"
)
Fonts that are supported on most platforms include "sans"
, "mono"
, "serif"
, "Times"
, "Helvetica"
, "Trebuchet"
, "Georgia"
, "Palatino"
or "Comic Sans"
.
Layers
Stack layers on top of each other
Import and scale images:
bigdata <- image_read('https://jeroen.github.io/images/bigdata.jpg')
frink <- image_read("https://jeroen.github.io/images/frink.png")
logo <- image_read("https://jeroen.github.io/images/Rlogo.png")
img <- c(bigdata, logo, frink)
img <- image_scale(img, "300x300")
image_info(img)
## format width height colorspace matte filesize
## 1 JPEG 300 225 sRGB FALSE 0
## 2 PNG 300 232 sRGB TRUE 0
## 3 PNG 148 300 sRGB TRUE 0
Print images:
# Prints images on top of one another
image_mosaic(img)
# Create a single image which has the size of the first image
image_flatten(img)
# Adding images
image_flatten(img, 'Add')
# Modulate images
image_flatten(img, 'Modulate')
# Minus
image_flatten(img, 'Minus')
Combining or appending images
Put the image frames next to each other:
image_append(image_scale(img, "x200"))
Stack images on top of each other:
image_append(image_scale(img, "100"), stack = TRUE)
Composing allows for combining two images on a specific position:
bigdatafrink <- image_scale(image_rotate(image_background(frink, "none"), 300), "x200")
image_composite(image_scale(bigdata, "x400"), bigdatafrink, offset = "+180+100")
Create GIF animation
Animating image frames:
image_animate(image_scale(img, "200x200"), fps = 1, dispose = "previous")
Creates a sequence of n
images that gradually morph one image into another.
newlogo <- image_scale(image_read("https://jeroen.github.io/images/Rlogo.png"))
oldlogo <- image_scale(image_read("https://developer.r-project.org/Logo/Rlogo-3.png"))
image_resize(c(oldlogo, newlogo), '200x150!') %>%
image_background('white') %>%
image_morph() %>%
image_animate()
Read more
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