[pdftex] bug with included transparent graphics

Victor Ivrii vivrii at gmail.com
Mon Dec 31 14:34:40 CET 2007

On Dec 31, 2007 8:24 AM, James Quirk <jjq at hmx.galcit.caltech.edu> wrote:
> On Mon, 31 Dec 2007, Victor Ivrii wrote:
> >
> > On Mac OSX 10.4.11, pdftex-1.40.3 neither AR 8.1.1 nor AR 7.0.9 nor 3
> > other pdf viewers show any difference between colors on the first and
> > second pages (I run few tests uncommenting corresponding lines). At
> > least for me. I am not sure how to measure accurately and objectively
> > colors (I cannot rely upon much on my eyes comparing two close
> > shades).
> On my Linux box I used kcolorchooser to measure the colors and
> I would guess that OSX provides a similar functionality.

Sure it does. I just do not trust my eyes (one wise man said "If you
see on the cage with the lion the plaque `it is a tiger`, then do not
trust your eyes" :)

> try the case:
> \pagecolor[HTML]{505050}  % page 2 is #021518

No visible difference for me (so far I was not considered to be
color-blind and if I insert after \newpage
\pagecolor[HTML]{021518} I do see the difference in shades of Darkness :)

> for which the change from page 1 (#505050) to page2 (#021518) is quite
> marked and your comments concerning visual perception do not apply.
> Actually, I've just tried it on my wife's XP box and there is no change in
> the page colours and so it looks like it is a Linux-specific bug. This is
> unfortunate as the pre-release program for Linux AR8.1.2 has just closed
> and so it might be some time before a bug fix can make it to a public AR
> release.

Did you try other PDF viewers on Linux? xpdf? I tried Skim and Apple
preview and built in pdfviewer of TeXShop and they consistently show
no difference.

> James
> >
> > However it is a well-known effect that the visual perception of the
> > same color changes if the surrounding objects change their colors; I
> > suspect that the degree of this illusion could be individual.

Victor Ivrii, Professor, Department of Mathematics, University of Toronto

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