alpha not working as expected with tm_basemap("Esri.WorldImagery"

[marine-ecologist]

(apologies in advance if this is a r graphics issue and not tmap related)

alpha_10 <- tm_layout(bbox=c(xmin=145.440, ymin=-14.710, xmax=145.464, ymax=-14.69), inner.margins=0.00) +
  tm_basemap("Esri.WorldImagery", alpha=0.1) 

alpha_100 <- tm_layout(bbox=c(xmin=145.440, ymin=-14.710, xmax=145.464, ymax=-14.69), inner.margins=0.00) +
  tm_basemap("Esri.WorldImagery", alpha=0.1) 


tmap_arrange(alpha_10, alpha_100, ncol=1)

[mtennekes]

Thx @marine-ecologist