Passing colors to Metafun and TeX's bitmapimage macros

Passing colors to Metafun and TeX's bitmapimage macros

[Jairo A. del Rio via ntg-context]

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Hi, list!
I want to know if there's a handy way to pass predefined colors, either RGB
or CMYK, e.g. those in svg or crayola, to Metafun's bitmapimage. Say,
something like:

\startMPpage

% svg's gold definition

draw bitmapimage(2, 2, "ffd700 ffd700 ffd700 000000") scaled 3cm;

\stopMPpage

using "gold" instead of its definition so that I can set bitmap image
colors by name rather than numbers. In a similar vein, I wonder if
something analogous is possible for ConTeXt's \bitmapimage macro. Thank you
in advance.

Cordially,

Jairo

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Re: Passing colors to Metafun and TeX's bitmapimage macros

[Hans Hagen via ntg-context]

On 9/1/2021 1:08 PM, Jairo A. del Rio via ntg-context wrote:
> Hi, list!
> I want to know if there's a handy way to pass predefined colors, either 
> RGB or CMYK, e.g. those in svg or crayola, to Metafun's bitmapimage. 
> Say, something like:
> 
> \startMPpage
> 
> % svg's gold definition
> 
> draw bitmapimage(2, 2, "ffd700 ffd700 ffd700 000000") scaled 3cm;
> 
> \stopMPpage
> 
> using "gold" instead of its definition so that I can set bitmap image 
> colors by name rather than numbers. In a similar vein, I wonder if 
> something analogous is possible for ConTeXt's \bitmapimage macro. Thank 
> you in advance.
it's mostly about 'what interface to use' and 'how is that documented 
and remembered at all'

\startluacode
     function MP.replacecolors(str,c)
         -- could be a helper, these two combined (never needed it):
         local m, a = attributes.colors.namedcolorattributes(c)
         local d = attributes.colors.values[a]
         local r = string.format("%02x%02x%02x",
             math.round(d[3]*255),
             math.round(d[4]*255),
             math.round(d[5]*255)
         )
         mp.quoted((string.gsub(str,"444444",r)))
     end
\stopluacode

\definecolor[kindofgold][h=ffd700]

\startMPpage

draw bitmapimage(2, 2, "ffd700 ffd700 ffd700 000000") scaled 3cm;

vardef mybitmapimage(expr n, m, s, c) =
     bitmapimage(2, 2, MP.replacecolors(s, c))
enddef ;

draw mybitmapimage(2, 2, "444444 444444 444444 000000", "kindofgold") 
scaled 3cm shifted (0,-3cm);

\stopMPpage




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