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Diffstat (limited to 'doc/user/bgr_colo')
| -rw-r--r-- | doc/user/bgr_colo | 31 |
1 files changed, 19 insertions, 12 deletions
diff --git a/doc/user/bgr_colo b/doc/user/bgr_colo index 08d8d2a..7da8eeb 100644 --- a/doc/user/bgr_colo +++ b/doc/user/bgr_colo @@ -32,21 +32,28 @@ The @Code "@Colour" symbol will accept any of the following colours: @Rowb A { black } B { white } } Monochrome output devices will render them as shades of grey. Colouring -something @Code white makes it invisible, which is sometimes useful. +something @Code white makes it invisible (unless it is being printed +on a coloured background), which is sometimes useful. @PP In addition to the list of colours given above, there is a special -colour called {@Code nochange} which produces the colour you already -happen to be using. +colour called {@Code nochange} which produces whatever colour you already +happen to be using; you can also use an empty object to ask for this. And +you can get lots more colours by specifying them using numbers, like this: +@ID @Code "{ rgb 0.5 0.5 1.0 } @Colour { Hello, world }" +which means use red at intensity 0.5, green at intensity 0.5, and +blue at intensity 1.0, producing +@ID { rgb 0.5 0.5 1.0 } @Colour { Hello, world } +In the strange world of colour coordinates, in which 0 is dark and 1 is +light, this is a light blue. You can also use the CMYK system if you +know what that is: +@ID @Code "{ cmyk 0.5 0.5 1.0 1.0 } @Colour { Hello, world }" +produces +@ID { cmyk 0.5 0.5 1.0 1.0 } @Colour { Hello, world } +Wherever in this document it says that that you can use any colour +from this section, it means any of the names above, or {@Code nochange}, +or an object beginning with @Code "rgb" or @Code "cmyk" as shown. @PP Whether or not the colours produced by @Code "@Colour" actually correspond with the names depends on the output device; the same -nominal colour can look quite different on screen and on paper. The -standard Lout @Code "@SetColour" symbol can provide many more colours -setcolour. @Index @Code "@SetColour" -@Cite { $kingston1995lout.expert}, although they must be specified -using numbers rather than names. For example, -@ID @Code "{ 0.5 0.5 1.0 } @SetColour Hello" -prints @Code Hello in a colour containing red at intensity 0.5, green -at intensity 0.5, and blue at intensity 1.0, which turns out, in the -strange world of colour coordinates, to be a light blue. +nominal colour can look quite different on screen and on paper. @End @Section |