Convert image to matrix in R

May 17, 2007
By

(This article was first published on Quantitative Ecology, and kindly contributed to R-bloggers)

This is how to use the Pixmap library to read in an image as a matrix.


> library(pixmap)
# the next command may only work on Linux
> system("convert foo.tiff foo.ppm")
> img <- read.pnm("foo.ppm")


To get info on your new object:

> str(img)

Although included in the previous output, the size of the image can be extracted by:

>img@size

Then to extract the red channel from the image for the first ten rows:

> myextract <- img@red[1:10,]

Or to extract the entire red channel to an actual matrix:

> red.mat<-matrix(NA,img@size[1],img@size[2])
> red.mat<-img@red

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