PBSmodelling: testAlpha – R documentation

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testAlpha

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, ...)

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

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

Jon T. Schnute, Pacific Biological Station, Fisheries and Oceans Canada, Nanaimo BC