colour_to_integer() for "transparent" and NA_character_ "colors"

[trevorld]

I'm observing that colour_to_integer() is casting "transparent" to an opaque color equivalent to "white" (with a message saying unknown color) and is casting NA_character_ to "#00000000" which is a fully transparent value but a slightly different fully transparent value from what col2rgb() assigns to it. I'd pedantically "expect" colour_to_integer(NA_character_) to instead return 16777215L (the same as colour_to_integer("#FFFFFF00")).

> library("nara")
> colour_to_integer("#FFFFFF00") |> integer_to_colour()
[1] "#ffffff00"
> colour_to_integer("transparent") |> integer_to_colour()
Unknown colour: transparent
[1] "#ffffffff"
> colour_to_integer(NA_character_) |> integer_to_colour()
[1] "#00000000"
> col2rgb(c("transparent", "#FFFFFF00", NA_character_, "white"),  
          alpha = TRUE)
      [,1] [,2] [,3] [,4]
red    255  255  255  255
green  255  255  255  255
blue   255  255  255  255
alpha    0    0    0  255

I've observed that farver::encode_native() also has trouble with these two edge cases: thomasp85/farver#47

[trevorld]

My understanding is that some graphic devices or image viewers don't support alpha transparency so this would be the difference between a "transparent" background being rendered "white" or "black" in such devices/programs...

[coolbutuseless]

Thanks for raising the issue.

transparent and NA_character now return the integer for #ffffff00