Image recognition with MxNet.

MxNet.R

require(devtools)
install_version("imager", version = "0.20", repos = "http://cran.us.r-project.org")

library("mxnet")
library(imager)
# can download the model from http://www.orbifold.net/default/R/MxNet/MxNetInception.zip

model = mx.model.load("Inception_BN", iteration=39)
mean.img = as.array(mx.nd.load("mean_224.nd")[["mean_img"]])
synsets <<- readLines("synset.txt")
im <- load.image("Parrots.jpg")
plot(im)

preproc.image <- function(im, mean.image) {
  shape <- dim(im)
  short.edge <- min(shape[1:2])
  xx <- floor((shape[1] - short.edge) / 2)
  yy <- floor((shape[2] - short.edge) / 2)
  croped <- crop.borders(im, xx, yy)
  resized <- resize(croped, 224, 224)
  arr <- as.array(resized) * 255
  dim(arr) <- c(224, 224, 3)
  normed <- arr - mean.img
  dim(normed) <- c(224, 224, 3, 1)
  return(normed)
}
normed <- preproc.image(im, mean.img)
prob <- predict(model, X=normed)
 
max.idx <- order(prob[,1], decreasing = TRUE)[1:5]
synsets[max.idx]