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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