Question

Inspired by this thread
How do I find Waldo with Mathematica?

I have never done image processing in R but maybe other people who have want to share…

thanks!

Answer 1

Here is a start, using the raster package. I don’t know if I will have the time to work on the cross-correlation method used in the Mathematica version of the question, but a local standard deviation on the red parts of the image seems to spot Waldo in this case…

library(raster)
waldo = stack("/Users/Benjamin/Desktop/DepartmentStore.jpg")

r = waldo[[1]] - waldo[[2]] - waldo[[3]]
r[is.na(r)] = 0
r_mask = Which(r > 0)
r_masked = r * r_mask

focalsd = focal(r_masked, w=3, fun=sd)
plot(focalsd)