testAlpha function

Test Various Alpha Transparency Values

Display how the alpha transparency for rgb() varies.

testAlpha(alpha=seq(0,1,len=25), fg="blue", bg="yellow",
      border="black", grid=FALSE, ...)

Arguments

• alpha: numeric -- vector of alpha transparency values values from 0 to 1.
• fg: character -- foreground colour of the top shape that varies in transparency.
• bg: character -- background colour (remains constant) of the underlying shape.
• border: character -- border colour (which also changes in transparency) of the foreground polygon.
• grid: logical -- if TRUE, lay a grey grid on the background colour.
• ...: dots -- additional graphical arguments to send to the the ploting functions.

Returns

Invisibly returns the compound RGB matrix for fg, alpha, bg, and border.

Author(s)

Jon T. Schnute, Research Scientist Emeritus

Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo BC

Maintainer: Rowan Haigh, Program Head -- Offshore Rockfish

Pacific Biological Station (PBS), Fisheries & Oceans Canada (DFO), Nanaimo BC

locus opus: Offsite, Vancouver BC

Last modified Rd: 2023-10-18

See Also

In package PBSmodelling:

testCol, testLty, testLwd

In package PBStools:

testPch