it is the behaviour of the (old) osx preview app for sure.
when looking at the pdf, the thumbnails are correct, however when focussing on the page it turns green.
its getting more urgent to move to Linux ;-)

.F




On 6 Dec 2018, at 11:12, luigi scarso <luigi.scarso@gmail.com> wrote:



On Thu, Dec 6, 2018 at 10:55 AM Floris van Manen <vm@klankschap.nl> wrote:
while experimenting with the sample transparency color code


\definecolor [transparentred]  [r=1,t=.5,a=1]
\definecolor [transparentblue] [b=1,t=.5,a=1]
\definecolor [solidyellow]  [y=1,t=1,a=1]

\starttext

\startTEXpage
~This is some sample text that goes behind the rectangles\hskip-80mm
\blackrule[width=18mm,height=10mm,depth=10mm,color=solidyellow]\hskip-6mm
\blackrule[width=18mm,height=20mm,depth=1mm,color=transparentred]\hskip-6mm
\blackrule[width=18mm,height=10mm,depth=10mm,color=transparentblue]\hskip-6mm
\blackrule[width=18mm,height=20mm,depth=1mm,color=solidyellow]\hskip27mm
\stopTEXpage

\stoptext



i get the intended result.

<Screen Shot 2018-12-06 at 10.53.21.PNG>

if i change the yellow t value to .99 
\definecolor [solidyellow]  [y=1,t=0.99,a=1]
some green layer pops up.



as this is all about software, there is a reason to this.
it cold be the OSX preview program too, of course.
can someone explain to me ?
:-)

here is ok under ubuntu
Can you convert pdf to png ? This should show almost the same png.

You can also prepend 
\nopdfcompression
and post the pdf.

\nopdfcompression
\definecolor [transparentred]  [r=1,t=.5,a=1]
\definecolor [transparentblue] [b=1,t=.5,a=1]
\definecolor [solidyellow]  [y=1,t=1,a=1]

\starttext

\startTEXpage
\definecolor [solidyellow]  [y=1,t=1,a=1]
~This is some sample text that goes behind the rectangles\hskip-80mm
\blackrule[width=18mm,height=10mm,depth=10mm,color=solidyellow]\hskip-6mm
\blackrule[width=18mm,height=20mm,depth=1mm,color=transparentred]\hskip-6mm
\blackrule[width=18mm,height=10mm,depth=10mm,color=transparentblue]\hskip-6mm
\blackrule[width=18mm,height=20mm,depth=1mm,color=solidyellow]\hskip27mm
\stopTEXpage


\startTEXpage
\definecolor [solidyellow]  [y=1,t=0.99,a=1]
~This is some sample text that goes behind the rectangles\hskip-80mm
\blackrule[width=18mm,height=10mm,depth=10mm,color=solidyellow]\hskip-6mm
\blackrule[width=18mm,height=20mm,depth=1mm,color=transparentred]\hskip-6mm
\blackrule[width=18mm,height=10mm,depth=10mm,color=transparentblue]\hskip-6mm
\blackrule[width=18mm,height=20mm,depth=1mm,color=solidyellow]\hskip27mm
\stopTEXpage


\stoptext

-- 
luigi
<Screen Shot 2018-12-06 at 10.48.56.PNG><Screen Shot 2018-12-06 at 10.53.21.PNG><Screen Shot 2018-12-06 at 10.48.56.PNG><Screen Shot 2018-12-06 at 10.48.56.PNG>___________________________________________________________________________________
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