Independent adjustment of picture and line transparency when using PhyloPic/Images and align=true parameter

[iliapopov17]

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When using geom_tiplab(), it would be useful to adjust the transparency of pictures and lines separately.

For example, when using:

test_tree <- ggtree(newick.tree) %<+% metadata + 
  geom_tiplab(image=df_sorted$uid,
              geom="phylopic",
              size = ifelse(df_sorted$uid == "6e42ac62-37f4-458c-bf44-3f7decb1f14e", 0.025, 0.05),
              alpha= ifelse(df_sorted$name == "NC_004290.1" | df_sorted$name == "NC_000936.1" | df_sorted$name == "NC_005040.1", 0.4, 0.8),
              offset = 1.5,
              align=TRUE) +
  xlim(0,5.2) + 
  geom_tiplab(
    aes(label=Full.Name),
    color="black",
    geom="label",
    fill = "white",
    label.size = 0
  )

I expect the alpha= parameter to adjust the transparency of the picture. But instead it adjusts the transparency of the line, since I have the align=TRUE parameter active.

In documentation of the geom_tiplab() function I did not find a solution to this problem. On the contrary, I was proved that it is not a bug, but a feature:

The following parameters for geom="image" or geom="phylopic".
- `image` the image file path for geom='image', but when geom='phylopic', it should be the uid of phylopic databases.
- `size` the image size, defaults to 0.05.
- `colour` the color of image, defaults to NULL.
- `alpha` the transparency of image, defaults to 0.8.

The following parameters for the line when align = TRUE.
- `colour` the colour of line, defaults to 'black'.
- `alpha` the transparency of line, defaults to NA.
- `arrow` specification for arrow heads, as created by arrow(), defaults to NULL.
- `arrow.fill` fill color to usse for the arrow head (if closed), defaults to 'NULL', meaning use 'colour' aesthetic.

I just want to adjust the transparency (and color too) of pictures separately from the line :(