Animated filling of a font character

Question

Is there a way to fill a sign, say the sign ' / ', with red in steps?

Because, I ask myself if I could create sth. like that, using the corresponding character from a matching font (in the picture U+3042 (12354)):

No MWE:

\documentclass[margin=5mm]{standalone}
\usepackage{tikz}
\begin{document}
Animate\tikz[scale=11, transform shape]\node{/};
\end{document}

Not using font files directly. It would involve quite a bit of handwork. On the other hand, if you have glyph examples based on plain strokes (as opposed to filled outlines) it could be done along the lines of this answer: https://tex.stackexchange.com/a/474914 . — AlexG, Jul 16 '20 at 11:14
Done! However, there are several unnecessary points which you need fix by yourself ... :-) — , Aug 01 '20 at 10:05

score 12 · Accepted Answer · 2020-08-01T16:38:21.640

Finished.

import animate;
settings.tex="xelatex";
settings.outformat="pdf"; 
texpreamble("\usepackage{CJK}
\usepackage{fontspec}
\setmainfont{Arial Unicode MS}
\AtBeginDocument{\begin{CJK}{UTF8}{name}}
\AtEndDocument{\clearpage\end{CJK}}");
animation Ani;
unitsize(1cm);
path[] Asymptote=texpath("あ");
// pen[] p={red,green,blue};
/*
for (int i=0; i <Asymptote.length; ++i)
{
  draw(Asymptote[i],p[i]);
}
*/
pair[] a,b,c;
pair labdira,labdirb,labdirc;
for(int j=0;j<size(Asymptote[0]);++j){
    a.push(point(Asymptote[0],j));
  }
    for(int j=0;j<size(Asymptote[1]);++j){
    b.push(point(Asymptote[1],j));
  }
    for(int j=0;j<size(Asymptote[2]);++j){
    c.push(point(Asymptote[2],j));
  }
path p1=subpath(Asymptote[0],21,22)--subpath(Asymptote[0],25,26);
path p2=reverse(subpath(Asymptote[0],19,20))--reverse(subpath(Asymptote[0],27,28));
path firstpath;
for(real r=0; r<20; ++r){
save();
firstpath=reverse(subpath(p2,0,reltime(p2,r/20)))--subpath(Asymptote[0],20,21)--subpath(p1,0,reltime(p1,r/20))--cycle;
fill(firstpath, (r != 0) ? black : invisible);
Ani.add();
restore();
}
fill(reverse(subpath(p2,0,reltime(p2,1)))--subpath(Asymptote[0],20,21)--subpath(p1,0,reltime(p1,1))--cycle);
path q1=reverse(subpath(Asymptote[0],22,23))--reverse(subpath(Asymptote[0],18,19))
               --subpath(Asymptote[2],1,0)--reverse(subpath(Asymptote[0],12,13));
path q2=subpath(Asymptote[0],24,25)--subpath(Asymptote[0],28,29)
               --subpath(Asymptote[1],2,3)--subpath(Asymptote[0],10,11);
path secondpath;
for(real r=0; r<20; ++r){
save();
secondpath=reverse(subpath(q1,0,reltime(q1,r/20)))--subpath(Asymptote[0],23,24)--subpath(q2,0,reltime(q2,r/20))--cycle;
fill(secondpath,(r != 0) ? black : invisible);
Ani.add();
restore();
}
fill(reverse(subpath(q1,0,reltime(q1,1)))--subpath(Asymptote[0],23,24)--subpath(q2,0,reltime(q2,1))--cycle);
pair A=b[0]+2dir(subpath(Asymptote[1],3,4));
pair B=a[9]+2dir(reverse(subpath(Asymptote[0],9,10)));
pair Aa=intersectionpoint(subpath(Asymptote[0],1,2),b[0]--A);
pair Bb=intersectionpoint(subpath(Asymptote[0],1,2),a[9]--B);
path tr=subpath(Asymptote[1],4,3)--subpath(Asymptote[2],6,1)
                   --subpath(Asymptote[1],2,0)
                   --reverse(subpath(Asymptote[0],6,9));
path tr1=subpath(Asymptote[0],9,10)
                   --subpath(Asymptote[0],13,18)
                   --subpath(Asymptote[0],0,5);
path kk;
for (int i=0; i<=20; ++i){
save();
  kk=reverse(subpath(Aa--tr,0,reltime(Aa--tr,i/20)))--Aa--Bb--subpath(Bb--tr1,0,reltime(Bb--tr1,i/20))--cycle;
  fill(kk,(i != 0 ) ? black : invisible);
Ani.add();
restore();
}
erase();
Ani.movie(BBox(2mm,Fill(pink)));

Updated!

This is what you want!

Step 1:

settings.tex="xelatex";
settings.outformat="pdf"; 
texpreamble("\usepackage{CJK}
\usepackage{fontspec}
\setmainfont{Arial Unicode MS}
\AtBeginDocument{\begin{CJK*}{UTF8}{name}}
\AtEndDocument{\clearpage\end{CJK*}}");
unitsize(1cm);
path[] Asymptote=texpath("あ");
pen[] p={red,green,blue}; p.cyclic=true;
for (int i=0; i <Asymptote.length; ++i)
{
  draw(Asymptote[i],p[i]);
}
pair[] a,b,c;
pair labdira,labdirb,labdirc;
for(int j=0;j<size(Asymptote[0]);++j){
    a.push(point(Asymptote[0],j));
    labdira=rotate(-90)dir(Asymptote[0],j);
    dot("$\scriptsize "+string(j)+"$",a[j],labdira);
  }
    for(int j=0;j<size(Asymptote[1]);++j){
    b.push(point(Asymptote[1],j));
    labdirb=rotate(-90)dir(Asymptote[1],j);
    dot("$\scriptsize "+string(j)+"$",b[j],labdirb);
  }
    for(int j=0;j<size(Asymptote[2]);++j){
    c.push(point(Asymptote[2],j));
    labdirc=rotate(-90)*dir(Asymptote[2],j);
    dot("$\scriptsize "+string(j)+"$",c[j],labdirc);
  }

Step 2:

import animate;
settings.tex="xelatex";
settings.outformat="pdf"; 
texpreamble("\usepackage{CJK}
\usepackage{fontspec}
\setmainfont{Arial Unicode MS}
\AtBeginDocument{\begin{CJK}{UTF8}{name}}
\AtEndDocument{\clearpage\end{CJK}}");
animation Ani;
unitsize(1cm);
path[] Asymptote=texpath("あ");
pen[] p={red,green,blue};
for (int i=0; i <Asymptote.length; ++i)
{
  draw(Asymptote[i],p[i]);
}
pair[] a,b,c;
pair labdira,labdirb,labdirc;
for(int j=0;j<size(Asymptote[0]);++j){
    a.push(point(Asymptote[0],j));
    /labdira=rotate(-90)dir(Asymptote[0],j);
    dot("$\scriptsize "+string(j)+"$",a[j],labdira);/
  }
    for(int j=0;j<size(Asymptote[1]);++j){
    b.push(point(Asymptote[1],j));
    /labdirb=rotate(-90)dir(Asymptote[1],j);
    dot("$\scriptsize "+string(j)+"$",b[j],labdirb);/
  }
    for(int j=0;j<size(Asymptote[2]);++j){
    c.push(point(Asymptote[2],j));
    /labdirc=rotate(-90)dir(Asymptote[2],j);
    dot("$\scriptsize "+string(j)+"$",c[j],labdirc);*/
  }
picture pic1;
pair Tmin=(a[21].x,a[20].y),Tmax=(a[27].x,a[26].y);
path g1=subpath(Asymptote[0],19,22)--subpath(Asymptote[0],25,28)--cycle;
for(real r=0; r<20; ++r){
save();
fill(pic1,g1);
clip(pic1,box(Tmin,relpoint((Tmin.x,Tmax.y)--Tmax,r/20)));
add(pic1);
Ani.add();
restore();
}
fill(g1);
picture pic2;
pair Tmin=(min(Asymptote[0]).x,a[12].y),Tmax=max(Asymptote[0]);
path g2=subpath(Asymptote[0],22,25)--
               //subpath(Asymptote[0],28,0)--
               a[28]--a[0]--
               subpath(Asymptote[1],2,3)--
               subpath(Asymptote[0],10,13)--
               subpath(Asymptote[2],0,1)--
               subpath(Asymptote[0],18,19)--cycle;
for(real r=0; r<20; ++r){
save();
fill(pic2,g2);
clip(pic2,box(relpoint((Tmin.x,Tmax.y)--Tmin,r/20),Tmax));
add(pic2);
Ani.add();
restore();
}
fill(g2);
picture pic3;
path tr=subpath(Asymptote[1],4,3)--subpath(Asymptote[2],6,1)
                   --subpath(Asymptote[1],2,0)
                   --reverse(subpath(Asymptote[0],6,9));
path tr1=subpath(Asymptote[0],9,10)
                   --subpath(Asymptote[0],13,18)
                   --subpath(Asymptote[0],0,5);
path kk;
for (int i=0; i<=20; ++i){
save();
  kk=reverse(subpath(tr,0,reltime(tr,i/20)))--b[0]--a[9]--subpath(tr1,0,reltime(tr1,i/20))--cycle;
  fill(pic3,kk);
  add(pic3);
Ani.add();
restore();
}
erase();
Ani.movie(BBox(3mm,Fill(white)));

This is my consideration for keyword "A" with Asymptote.

As AlexG's comment: It would involve quite a bit of handwork.

Only for compare and checking purpose.

import animate;
settings.tex="pdflatex"; 
settings.outformat="pdf";
animation Ani;
size(10cm);
path[] Asymptote=texpath(Label("A"));
pen[] p={red,green,blue}; p.cyclic=true;
for (int i=0; i <Asymptote.length; ++i)
{
  draw(Asymptote[i],p[i]);
}
pair[] a,b;
pair labdira,labdirb;
for(int j=0;j<size(Asymptote[0]);++j){
    a.push(point(Asymptote[0],j));
    /labdira=rotate(-90)dir(Asymptote[0],j);
    dot("$\scriptsize "+string(j)+"$",a[j],labdira);/
  }
    for(int j=0;j<size(Asymptote[1]);++j){
    b.push(point(Asymptote[1],j));
    /labdirb=rotate(-90)dir(Asymptote[1],j);
    dot("$\scriptsize "+string(j)+"$",b[j],labdirb);/
  }
pair M=intersectionpoint(subpath(Asymptote[0],0,1),b[0]--b[0]+(b[0]-b[2]));
path d=subpath(Asymptote[0],intersect(subpath(Asymptote[0],0,1),b[0]--b[0]+(b[0]-b[2]))[0],11)--b[2]--b[0]--cycle;
path q=b[0]--b[1]--subpath(Asymptote[0],12,20)--subpath(Asymptote[0],0,intersect(subpath(Asymptote[0],0,1),b[0]--b[0]+(b[0]-b[2]))[0])--cycle;
//dot(M);
pair K=min(Asymptote[0]),U=max(Asymptote[0]);
draw(box(K,U));
picture pic1;
for(real r=0; r<20; ++r){
save();
fill(pic1,d,red);
clip(pic1,box(K,relpoint((U.x,K.y)--U,r/20)));
add(pic1);
Ani.add();
restore();
}
fill(d,red);
picture pic2;
for(real r=0; r<20; ++r){
save();
fill(pic2,q,red);
clip(pic2,box(relpoint((K.x,U.y)--K,r/20),U));
add(pic2);
Ani.add();
restore();
}
fill(q,red);
pair Mi=(a[11].x,K.y),Ma=(a[12].x,U.y);
picture pic3;
for(real r=0; r<=20; ++r){
save();
fill(pic3,(a[11]--b[2]--b[1]--a[12]--cycle),red);
clip(pic3,box(Mi,relpoint((Mi.x,Ma.y)--Ma,r/20)));
add(pic3);
Ani.add();
restore();
}
erase();
Ani.movie(BBox(3mm,Fill(white)));

Wow, this is quite impressive! I have to study your procedure. — cis, Aug 01 '20 at 10:19
The bronze medal is well merited. I'm glad there's a great user with Asymptote. — Sebastiano, Aug 02 '20 at 08:21

Animated filling of a font character

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