Legend colors do not match map colors

[Fred-Wu]

This is similar to an old issue #219 , but a bit long time ago. So I hope it is OK for me to open a new one.

I used brewer.pal from RColorBrewer package to prepare the col.regions with 5 groups. However, the region colors look different from the ones on the legend.

I think this has something to do with alpha.regions in the first output, but not sure why leaflet would be more similar here.

colRegions <- colorRampPalette(brewer.pal(5, 'YlOrRd'))
b <- mapview(sa3, zcol = "AREASQKM16",
        at = quantile(sa3$AREASQKM16, prob = seq(0, 1, length.out=6)),
        color = NA, map.types = "OpenStreetMap",
        layer.name = "Area in km^20",
        col.regions = colRegions)

The region colors are more similar to the one with addLegend if I clear the legend control and add legend with leaflet function.

colPal <- colorQuantile("YlOrRd", n = 5, domain = sa3$AREASQKM16)
b@map %>% clearControls() %>% addLegend(position = "topright", 
                pal = colPal, title = "Area in km^2",
                values = sa3$AREASQKM16,
                labFormat = function(type, cuts, p) {
                  n = length(cuts)
                  paste0(cuts[-n], " &ndash; ", cuts[-1])
                })

[tim-salabim]

Yeah, that's a tricky one and there is no clear solution here. The legend colors have a alpha of 1 whereas the the polygons are filled with an alpha of 0.6 by default (I think). The colors in the legend can only ever match the ones on the map if both are completely opaque. Otherwise their values will depend on what's behind them, i.e. the location on the map...
That said, there was a bug I recently addressed which would lead to these fully opaque legends. When you re-install from here, you can control legend.opacity via the options.