Resizing image in R

Question

I am trying to work with some image data in R, and cannot figure out how to resize the images I have to ensure they are all the same size.

In Python, I approached this problem as follows:

from PIL import Image
import numpy as np

size = (100, 100)
img = Image.open(filename)
img = img.resize(size)
img = np.array(img.getdata())

In R, I've been unable to locate a library that would accomplish the same thing. The farthest I've been able to get is:

library(jpeg)

img <- readJPEG(filename)
# Need something here to resize
img <- as.matrix(img)

The easiest approach would be a library like Pillow that I could call on, but as I said, I can't seem to find anything.

Thanks,

Answer 1

You can easily accomplish this with the help of the Bioconductor package EBImage, an image processing and analysis toolbox for R. To install the package use:

source("http://bioconductor.org/biocLite.R")
biocLite("EBImage")

You can then use the functionality provided by EBImage to load and scale the image, as in the following example.

library("EBImage")

x <- readImage(system.file("images", "sample-color.png", package="EBImage"))

# width and height of the original image
dim(x)[1:2]

# scale to a specific width and height
y <- resize(x, w = 200, h = 100)

# scale by 50%; the height is determined automatically so that
# the aspect ratio is preserved
y <- resize(x, dim(x)[1]/2)

# show the scaled image
display(y)

# extract the pixel array
z <- imageData(y)

# or
z <- as.array(y)

For more examples on the functionality provided by EBImage see the the package vignette .

Answer 2

The package imager is a nice fit and hides all the details about splines, interpolations and simply stores the images in a 4 dimensional array (the fourth dimension being used in the case of videos)

library(imager)

im <- load.image(my_file)

thmb <- resize(im,round(width(im)/10),round(height(im)/10))

plot(im)
plot(thmb,main="Thumbnail")

More informations can be found here: on the official introduction.