Re: [NTG-context] METAPOST/MetaFun withtransparency doesn't accept my pair primary argument, what am I doing wrong?

10 Apr 2020


      As I only use one transparency method anyway I could also fix this by passing a numeric instead of a pair and use the standard withtransparency (I don’t like overriding a standard MetaFun method, one never knows what might break in future updates).

vardef Foo( expr w, h, fillColor, fillTransparency) =
  show "FOO:", w, h, fillColor, fillTransparency;
  save pic; picture pic;
  save circ; path circ;
  circ := (fullcircle xyscaled (h,h));
  pic := image (
    fill (circ shifted (w-h/2,-h/2)) withcolor fillColor withtransparency (1,fillTransparency);
  );
  pic
enddef;

picture pic;
pic := Foo( 150, 50, (0.686,1.000,1.000), 0.5);
draw pic;
\stopMPpage
\stoptext
...
On 9 Apr 2020, at 18:06, Hans Hagen  wrote:
On 4/9/2020 4:58 PM, Gerben Wierda wrote:
...
\starttext
\startMPpage[instance=doublefun]
vardef Foo( expr w, h, fillColor, fillTransparency) =
  show "FOO:", w, h, fillColor, fillTransparency;
  save pic; picture pic;
  save circ; path circ;
  circ := (fullcircle xyscaled (h,h));
  pic := image (
    fill (circ shifted (w-h/2,-h/2)) withcolor fillColor withtransparency fillTransparency;
  );
  pic
enddef;
pic := Foo( 150, 50, (0.686,1.000,1.000), (1,1.000));
draw pic;
\stopMPpage
\stoptext
Maybe this definition is better then but I need to test it more
\starttext
\startMPpage[instance=doublefun]
def withtransparency expr t =
   if pair t :
       withprescript "tr_alternative="  & decimal transparency_alternative_to_number(xpart t)
       withprescript "tr_transparency=" & decimal ypart t
   else :
       mfun_with_transparency (transparency_alternative_to_number(t))
   fi
enddef ;
def mfun_with_transparency (expr a) expr t =
   withprescript "tr_alternative="  & decimal a
   withprescript "tr_transparency=" & decimal t
enddef ;
vardef Foo ( expr w, h, fillColor, fillTransparency) =
 image (
   fill fullcircle xyscaled (h,h) shifted (w-h/2,-h/2)
       withcolor fillColor
       withtransparency fillTransparency
   ;
 )
enddef;
vardef FooX ( expr w, h, fillColor) =
 image (
   fill fullcircle xyscaled (h,h) shifted (w-h/2,-h/2)
       withcolor fillColor
       withtransparency (normaltransparent, .5)
   ;
 )
enddef;
vardef FooY ( expr w, h, fillColor) =
 image (
   fill fullcircle xyscaled (h,h) shifted (w-h/2,-h/2)
       withcolor fillColor
       withtransparency normaltransparent .5
   ;
 )
enddef;
draw Foo  ( 350, 50, (0.5,1,0), (1,.5));
draw FooX ( 250, 50, (1,0.5,1));
draw FooY ( 150, 50, (1,1,0.5));
\stopMPpage
\stoptext
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