Set the transparency / saturation of the palette in ggplot

Question

Start with the palette viridis. In my opinion, the colors are too bright for me, and for my purposes they look too artificial. so I would like to apply some transparency or similar to reduce saturation:

library(nord)
library(scales)
library(viridis)
library(nord)

show_col(viridis(5))
show_col(viridis(5, alpha=.5))

Applying alpha transparency internally seems to work. .

However, when it starts in ggplot, it automatically changes the alpha value to 1 and sets the full viridis intensity:

ggplot(faithfuld, aes(waiting, eruptions)) +
  geom_raster(aes(fill = density)) +
  scale_fill_viridis(5, alpha=.5)

In another example, I found the opposite problem, lack of intensity / saturation. For example, the "shine" palette from the package is nordgorgeous, but it looks a bit dull, lacks saturation, at least for my purposes.

show_col(nord("aurora",5))

, , 1, viridis, .

show_col(nord("aurora", alpha=.5))

alpha(). , .

show_col(alpha(nord("aurora",5)), .5)

/ viridis nord ggplot?

Answer 1

viridis, , . , viridis, . - , ( viridis) hsv, saturation value, .

. , .

vir_lite = function(cols, ds=0.4, dv=0.7) {
  cols = rgb2hsv(col2rgb(cols))
  cols["v", ] = cols["v", ] + dv*(1 - cols["v", ])
  cols["s", ] = ds*cols["s", ]
  apply(cols, 2, function(x) hsv(x[1], x[2], x[3]))
}

viridis:

show_col(viridis(5))

:

show_col(vir_lite(viridis(5)))

, ds dv. :

p = ggplot(faithfuld, aes(waiting, eruptions)) +
      geom_raster(aes(fill = density))

p + scale_fill_gradientn(colors=vir_lite(viridis(5)))

p + scale_fill_gradientn(colors=vir_lite(viridis(5), ds=0.6, dv=0.5))

Answer 2

- geom_raster():

ggplot(faithfuld, aes(waiting, eruptions)) +
    geom_raster(alpha = 0.5, aes(fill = density)) +
    scale_fill_viridis(5)

Answer 3

You have a small typo in your last function. .5is within show_col, not inside alpha. Thus, inside show_colit is interpreted as rounded 1, and it is logical TRUE, which leads to the display of HEX values.

So the correct line will be

show_col(alpha(nord("aurora",5), .5))

And it creates faint colors.