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The watershed transform is a label propagation algorithm. The value of non-zero pixels will get propagated to their zero-value neighbours. The propagation is controlled by a priority map. See examples.
watershed(im, priority, fill_lines = TRUE)an image
Priority map.
Sets if watershed lines must be filled or not.
cimg.limit.openmp()
#In our initial image we'll place three seeds
#(non-zero pixels) at various locations, with values 1, 2 and 3.
#We'll use the watershed algorithm to propagate these values
imd <- function(x,y) imdirac(c(100,100,1,1),x,y)
im <- imd(20,20)+2*imd(40,40)+3*imd(80,80)
layout(t(1:3))
plot(im,main="Seed image")
#Now we build an priority map: neighbours of our seeds
#should get high priority.
#We'll use a distance map for that
p <- 1-distance_transform(sign(im),1)
plot(p,main="Priority map")
watershed(im,p) %>% plot(main="Watershed transform")
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