%D \module
%D   [       file=meta-imp-noise,
%D        version=2025.11.12,
%D          title=\METAPOST\ Graphics,
%D       subtitle=Perlin Noise,
%D         author=Hans Hagen,
%D           date=\currentdate,
%D      copyright={PRAGMA ADE \& \CONTEXT\ Development Team}]
%C
%C This module is part of the \CONTEXT\ macro||package and is
%C therefore copyrighted by \PRAGMA. See mreadme.pdf for
%C details.

%D Exactly a year ago the meta-imp-perlin module was made for Keith McKay, That one
%D implemented Perlin Noise in pure \METAPOST. In the meantime we have native noise
%D in the engine as well as an interface, so here is an application.

% todo: reserved bytemaps

\startMPdefinitions
    def PerlinOverlay(expr kind, min, max, med, n, code) =
        numeric resolution ; resolution := 5 ;
        numeric variation ; variation := 100 ;
        numeric nx ; nx := resolution * round(OverlayWidth +2OverlayOffset);
        numeric ny ; ny := resolution * round(OverlayHeight+2OverlayOffset);
        numeric lw ; lw := resolution * round(OverlayLineWidth);
        picture p ; p := image ( draw lmt_noise [
            bytemap = 3,
            nx      = nx,
            ny      = ny,
            nz      = n,
            method  = "detail",
            minimum = min,
            maximum = max,
          colorcode = code,
            z       = if variation <> 0 : uniformdeviate fi variation,
        ] ) ;
        if kind == 0 :
            % frame
            setbyte (lw,lw,nx-2lw,ny-2lw) of 3 to 255 ;
        elseif kind == 1 :
            % fill
        elseif kind == 2 :
            % both (range)
            setbyte (lw,lw,nx-2lw,ny-2lw) of 3 to (med,max) ;
        fi ;
        draw p
            xysized (OverlayWidth,OverlayHeight)
        ;
    enddef ;
\stopMPdefinitions

\startuseMPgraphic{perlinframe}{min,max}
    PerlinOverlay(0, \MPvar{min}, \MPvar{max}, \MPvar{med}, 1, "") ;
\stopuseMPgraphic

\startuseMPgraphic{perlinbackground}{min,max}
    PerlinOverlay(1, \MPvar{min}, \MPvar{max}, \MPvar{med}, 1, "") ;
\stopuseMPgraphic

\startuseMPgraphic{perlincombined}{min,max}
    PerlinOverlay(2, \MPvar{min}, \MPvar{max}, \MPvar{med}, 1, "") ;
\stopuseMPgraphic

\defineoverlay
  [perlinframe]
  [\useMPgraphic{perlinframe}{min=125,max=250,med=125}]

\defineoverlay
  [perlinbackground]
  [\useMPgraphic{perlinbackground}{min=220,max=250,med=220}]

\defineoverlay
  [perlincombined]
  [\useMPgraphic{perlincombined}{min=125,max=250,med=200}]

\continueifinputfile{meta-imp-noise.mkxl}

\starttext

\framed
  [align=normal,
   frame=off,
   offset=4pt,
   background=perlinframe,
   rulethickness=4pt]
  {\samplefile{ward}}

\blank

\framed
  [align=normal,
   frame=off,
   offset=4pt,
   background=perlinbackground,
   rulethickness=4pt]
  {\samplefile{ward}}

\blank

\framed
  [align=normal,
   frame=off,
   offset=4pt,
   background=perlincombined,
   rulethickness=4pt]
  {\samplefile{ward}}

\defineoverlay
  [perlinbackground]
  [\useMPgraphic{perlinbackground}{min=230,max=250,med=230}]

\blank

\framed
  [align=normal,
   frame=off,
   offset=4pt,
   background=perlinbackground,
   rulethickness=4pt]
  {\samplefile{ward}}

\blank

\switchtobodyfont[bonum]

\startuseMPgraphic{perlinbackground}{min,max}
%     PerlinOverlay(1, 50, 255, 3, "v/1.2, v/1.4, v") ;
    PerlinOverlay(1, 50, 255, 50, 3, "1-v, 0, v") ;
\stopuseMPgraphic

\framed
  [align=normal,
   frame=off,
   offset=4pt,
   foregroundstyle=bold,
   foregroundcolor=white,
   background=perlinbackground,
   rulethickness=4pt]
  {\samplefile{ward}}

\stoptext