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.
- For Mac OS or Windowns:
- For Linux, you can install from source
- Install system requirements:
sudo apt-get install -y libmagick++-dev
- Install the R package
Load the package
Formats supported by ImageMagick on your system
## 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)
path is a filename,
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.
- 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.
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 out
+50pxfrom the left
image_scale(image, geometry = "200"): resize proportionally to width:
image_scale(image, grometry = "x200"): resize proportionally to height:
image_fill(image, color = "blue", point = "+100+200"): flood fill with blue starting at the point at
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")
Crop the image. Options are here
+50px from the left
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)
image_fill we can flood fill starting at pixel
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.
# 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
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
# 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:
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()
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Unable to locate appropriate package to print single max and mode grayscale values for image either individually (as image, as matrix or as vector). Looking to recapitulate Measure() from ImageJ. Magick returns un-useable format ‘magick-image’ that cannot be converted/read as jpeg. Imager gives nonsense values for every column of image as an array. I have some fundamental misunderstanding and don`t know where to start. Any pointers appreciated.