[luatex] png inclusion differs luatex vs pdftex

[luigi scarso]

On Tue, 30 Apr 2024 at 10:01, Linas Stonys <lstonys at vtex.lt> wrote:

> I get different colors of png image (attached europe.png) when I
> compile  lualatex and pdfflatex.
> Image contains some "transparency group".
> Differences are seen in acrobat but pdfxchange and sumatra shows the
> same (normaly like pdflatex did)
> See attached wrong_image_diff.png.
>
> Here's what one expert told me about pdfs with this  image:
> """
> pdflatex inserts parameters dictionary 'Group' inside the page
> dictionary and luatex doesn't.
> Acrobat precisely interprets all parameters that's why the view is
> different. Other viewers
> work mach simpler and the view gets the same.
> 'transparency group' mast exists because image is with the 'soft mask'
> which
> meant that image mast be painted with 'transparent imaging model'.
> I guess that luatex  draws image with 'opaque imaging model'
> """
>
> I hope you'll understand this comment (I translated it to english :))
> Could luatex load png  like pdftex does?
>
>
In context mkiv  this seems to be ok:

%%\nopdfcompression
\TransparencyHack
\starttext
\externalfigure[europe.png]
TEXT
\stoptext

Perhaps in lualatex there is something similar ?

--
luigi
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