[Xy-pic] Default color model

[Ross Moore]

On 04/08/2010, at 5:47 AM, Ross Moore <ross.moore at mq.edu.au> wrote:

> Also whether '0 setgray' gives black or white.
> 
> 
>> that I have to change?  And is
>> 
>> /xycolor{0 setgray}def
> 
> Yes, this forces a single color.
> 
> Another way is to define setrgbcolor to throw away 2 components and invert the 3rd.
> E.g.  /setrgbcolor{pop pop 1 sub neg}def

Oops. 0 setgray is black, right?
Then this should be 
   /setrgbcolor{pop pop setgray}def

> Or take a weighted sum of the components to convert to grayscale
>   /setrgbcolor{1 sub .6 mul neg 
>             exch 1 sub .15 mul neg add
>             exch 1 sub .25 mul neg add
>             }def

And this should be

       /setrgbcolor{1 sub neg .6 mul
                 exch 1 sub neg .15 mul add
                 exch 1 sub neg .25 mul add
                         1 sub neg setgray}def

> 
> And it is good to have this problem and solution in the Xy-pic mailing list archives.
> 

Sorry for the error.

Cheers,

    Ross