Imager is an image/video processing package for R, based on CImg, a C++ library by David Tschumperlé. CImg provides an easy-to-use and consistent API for image processing, which imager largely replicates. CImg supports images in up to four dimensions, which makes it suitable for applications like video processing/hyperspectral imaging/MRI.
Install the devtools package if you haven't already. Then run:
library(devtools)
install_github("dahtah/imager")
So far the package is only available as source code, so you'll need a functional R build environment (Rtools on Windows, XCode on OS X). To build under Linux make sure you have the headers for libX11.
You'll also need ImageMagick and ffmpeg if you want to be able to import and save images.
tennis <- load.image(system.file('extdata/tennis_sif.mpeg',package='imager'))
play(tennis)
#now filter in the time direction and pipe to play
deriche(tennis,10,axis="z") %>% play
Documentation is available here. To get a list of all package functions, run: ls(pos = "package:imager")
All images are stored as standard R numeric vectors (i.e., double-precision), meaning that they take up a lot of memory. It's easy to underestimate how much storage you need for videos, because they take up so little space in a compressed format. Before you can work on it in R a video has to be fully decompressed and stored as double-precision floats. To get a sense of the size, consider a low-resolution (400x300), colour video lasting 120 sec. The video might take up a few MBs when compressed. To store it in memory, you'll need: (400x300) x (25x120) x 3 values, corresponding to (space)x(time)x(colour). In addition, each value costs 8 bytes of storage, for a grand total of 8GB of memory.
Future versions of imager will have facilities for out-of-memory storage of video data, but in the meantime don't try to load large videos.
- Most CImg functions for filtering, morphology and colourspace conversions have R interfaces. The function calls and documentation is mostly verbatim copy from the original C++ API.
- There isn't a whole lot of argument checking so you might crash your session if you try something unexpected. Please report it if that happens.