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<div class="moz-cite-prefix">Minimal reproducible example:</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"><font face="monospace">#include
<cairo/cairo.h><br>
#include <cairo/cairo-pdf.h><br>
<br>
</font></div>
<div class="moz-cite-prefix"><font face="monospace">int main()<br>
{<br>
cairo_surface_t *sfc = cairo_pdf_surface_create("out.pdf",
100, 100);<br>
cairo_t *cr = cairo_create(sfc);<br>
<br>
// prepare some background<br>
cairo_set_source_rgb(cr, 0.7, 1.0, 1.0);<br>
cairo_paint(cr);<br>
<br>
cairo_set_operator(cr, CAIRO_OPERATOR_OVER);<br>
cairo_set_source_rgb(cr, 0.0, 0.0, 0.0);<br>
cairo_move_to(cr, 2.0, 2.0);<br>
cairo_line_to(cr, 98.0, 98.0);<br>
cairo_stroke(cr);<br>
<br>
cairo_push_group(cr);<br>
cairo_set_source_rgb(cr, 1.0, 1.0, 0.0);<br>
cairo_rectangle(cr, 10.0, 10.0, 80.0, 30.0);<br>
cairo_fill(cr);<br>
<br>
cairo_pattern_t *p1 = cairo_pop_group(cr);<br>
</font><br>
<font face="monospace"><font face="monospace">#if 1<br>
</font>
</font>
<div class="moz-cite-prefix"><font face="monospace"> // Problem
only manifests, when clipping is enabled<br>
</font></div>
<div class="moz-cite-prefix"><font face="monospace">
cairo_rectangle(cr, 0.0, 0.0, 100.0, 99.0);<br>
cairo_clip(cr);<br>
#endif</font></div>
<br>
<font face="monospace"> cairo_set_operator(cr,
CAIRO_OPERATOR_MULTIPLY);<br>
cairo_set_source(cr, p1);<br>
cairo_paint(cr);</font></div>
<div class="moz-cite-prefix"><font face="monospace"><br>
</font></div>
<div class="moz-cite-prefix"><font face="monospace">
cairo_translate(cr, 0.0, 50.0);<br>
cairo_set_source(cr, p1); // source has cached the ctm ->
needs update<br>
cairo_paint(cr);<br>
<br>
cairo_pattern_destroy(p1);<br>
<br>
cairo_surface_write_to_png(sfc, "out.png");<br>
<br>
cairo_destroy(cr);<br>
cairo_surface_destroy(sfc);<br>
<br>
return 0;<br>
}<br>
</font></div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">out.png is correct, out.pdf is not.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Comparison of pdf content streams:</div>
<div class="moz-cite-prefix">-- w/o clipping: --<br>
</div>
<div class="moz-cite-prefix"><font face="monospace">1 0 0 -1 0 100
cm<br>
q<br>
0.7 1 1 rg /a0 gs<br>
0 0 100 100 re f<br>
0 0 0 RG 2 w<br>
0 J<br>
0 j<br>
[] 0.0 d<br>
10 M 2 2 m 98 98 l S<br>
/b14 gs<br>
q<br>
/a0 gs /x6 Do<br>
Q<br>
q<br>
1 0 0 1 0 50 cm<br>
/a0 gs /x6 Do<br>
Q<br>
Q</font></div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">-- vs. w/ clipping: --<br>
</div>
<font face="monospace">1 0 0 -1 0 100 cm<br>
</font>
<div class="moz-cite-prefix"><font face="monospace">q<br>
0.7 1 1 rg /a0 gs<br>
0 0 100 100 re f<br>
0 0 0 RG 2 w<br>
0 J<br>
0 j<br>
[] 0.0 d<br>
10 M 2 2 m 98 98 l S<br>
Q q<br>
0 0 100 99 re W n<br>
/b14 gs<br>
q<br>
/a0 gs /x6 Do<br>
Q<br>
Q q<br>
0 50 100 49 re W n<br>
q<br>
1 0 0 1 0 50 cm<br>
/a0 gs /x6 Do<br>
Q<br>
Q</font><br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">The change of clipping (translate...)
adds another level of q/Q grouping to limit its effect, but the
group also contains and limits the /b14 gs command – and the /b14
is not emitted again in the second group, although MULTIPLY should
still be used.<br>
</div>
<p> Tobias<br>
</p>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">On 03/11/2022 16:30, Tobias Hoffmann
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:ae9c5c4c-388a-3926-b881-6249dce80a12@thax.hardliners.org">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<div class="moz-cite-prefix">I did some more research and ltrace'd
pdftocairo --pdf and --png.</div>
<div class="moz-cite-prefix">There is no obvious difference in the
cairo call that generate the highlight.</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Next, I compared the cairo commands
producing the first highlight ("small") with those of the second
highlight ("Virtual Mechanics"). Apart from some differing
address, the only major difference is an additional
cairo_pattern_destroy:<br>
</div>
<div class="moz-cite-prefix"><font face="monospace"><br>
</font></div>
<font face="monospace">[...cairo_clip, etc....]<br>
// CairoOutputDev::beginTransparencyGroup<br>
//
<a class="moz-txt-link-freetext"
href="https://github.com/freedesktop/poppler/blob/bc4a0d9a2abfcd75d9b0ee4be3f7600905fe6001/poppler/CairoOutputDev.cc#L906"
moz-do-not-send="true">https://github.com/freedesktop/poppler/blob/bc4a0d9a2abfcd75d9b0ee4be3f7600905fe6001/poppler/CairoOutputDev.cc#L906</a><br>
cairo_get_matrix(0x56e2e080, 0x56eabc08, 2, 0xf7095466)
= 0x56eabc08<br>
cairo_push_group(0x56e2e080, 0x56eabc08, 2,
0xf7095466) = 0<br>
cairo_set_operator(0x56e2e080, 2, 2,
0xf7095466) = 0<br>
cairo_save(0x56e2e080, 0, 0xf79509a9,
0xf7b55184) = 0<br>
cairo_pattern_reference(0x56e2e830, 0, 0xf79509a9,
0xf7b55184) = 0x56e2e830<br>
cairo_pattern_reference(0x56e2e830, 0, 0xf79509a9,
0xf7b55184) = 0x56e2e830<br>
cairo_pattern_get_type(0x56e2e830, 0x56eac04c, 0xffd4a260,
0xf791e9f8) = 0<br>
cairo_pattern_destroy(0x56e2e830, 0x56eac04c, 0xffd4a260,
0xf791e9f8) = 10<br>
<br>
cairo_pattern_create_rgba(0, 0x3ff00000, 0,
0x3ff00000) = 0x56eab410<br>
cairo_new_path(0x56e2e080, 0, 0,
7) = 0<br>
cairo_move_to(0x56e2e080, 0x28f5c290, 0x405b5f5c,
0x51eb851f) = 0<br>
cairo_curve_to(0x56e2e080, 0xcccccccd, 0x405acccc,
0xc28f5c29) = 0<br>
cairo_line_to(0x56e2e080, 0xeb851eb8, 0x40614851,
0x8f5c28f6) = 0<br>
cairo_curve_to(0x56e2e080, 0x9999999a, 0x40619199,
0x1eb851eb) = 0<br>
cairo_set_fill_rule(0x56e2e080, 0, 0x56eabfd0,
0x56eabbb0) = 0<br>
cairo_set_source(0x56e2e080, 0x56eab410, 0x56eabfd0,
0x56eabbb0) = 0<br>
cairo_fill(0x56e2e080, 0x56eab410, 0x56eabfd0,
0x56eabbb0) = 0<br>
cairo_restore(0x56e2e080, 744, 0xf78ea873,
0x56594bdc) = 0<br>
cairo_pattern_destroy(0x56eab410, 744, 0xf78ea873,
0x56594bdc) = 0<br>
cairo_pattern_destroy(0x56e2e830, 744, 0xf78ea873,
0x56594bdc) = 9<br>
<br>
cairo_set_operator(0x56e2e080, 2, 2,
0x565abb00) = 0<br>
// Next line is only present for the second highlight ->
CairoOutputDev::endTransparencyGroup<br>
cairo_pattern_destroy(0x56e30cd0, 0xf78ffab0, 0xf78f46b9,
0xf7b55184) = 0<br>
cairo_pop_group(0x56e2e080, 0xf78ffab0, 0xf78f46b9,
0xf7b55184) = 0x56e30cd0 // (retval same for both!)<br>
cairo_restore(0x56e2e080, 0xf78ffab0, 0xf78f25e9,
0x56594bdc) = 0<br>
cairo_pattern_destroy(0x56e2e830, 0xf78ffab0, 0xf78f25e9,
0x56594bdc) = 8<br>
cairo_pattern_destroy(0x56e2e830, 0xf78ffab0, 0xf78f25e9,
0x56594bdc) = 7<br>
<br>
// CairoOutputDev::paintTransparencyGroup<br>
cairo_set_operator(0x56e2e080, 14, 0xf7b55184,
0x565abb00) = 0<br>
cairo_save(0x56e2e080, 0xffd4a6e4, 0xf78f4889,
0x56597a6c) = 0<br>
cairo_set_matrix(0x56e2e080, 0x56eabc08, 0xf78f4889,
0x56597a6c) = 0<br>
cairo_set_source(0x56e2e080, 0x56e30cd0, 0xf78f4889,
0x56597a6c) = 0<br>
cairo_paint_with_alpha(0x56e2e080, 0, 0x3ff00000,
0x56597a6c) = 0<br>
cairo_status(0x56e2e080, 0, 0x3ff00000,
0x56597a6c) = 0<br>
_ZdlPvj(0x56eabc00, 60, 0x3ff00000,
0x56597a6c) = 0<br>
cairo_restore(0x56e2e080, 60, 0x3ff00000,
0x56597a6c) = 0<br>
<br>
cairo_restore(0x56e2e080, 32, 0xf78f25e9,
0x56594bdc) = 0<br>
cairo_pattern_destroy(0x56e2e830, 32, 0xf78f25e9,
0x56594bdc) = 6<br>
cairo_pattern_destroy(0x56e2e830, 32, 0xf78f25e9,
0x56594bdc) = 5<br>
<br>
cairo_set_operator(0x56e2e080, 2, 0xf7b55184,
0x565abb00) = 0<br>
cairo_restore(0x56e2e080, 744, 0xffd4add4,
0x56594bdc) = 0<br>
cairo_pattern_destroy(0x56e2e830, 744, 0xffd4add4,
0x56594bdc) = 4<br>
cairo_pattern_destroy(0x56e2e830, 744, 0xffd4add4,
0x56594bdc) = 3</font><br>
<br>
<div class="moz-cite-prefix">I believe cairo_set_operator(,14,) in
paintTransparencyGroup should output a gs change in BOTH cases,
but it's only for the first case when using a PDF surface; OTOH,
when the context is backed by a Image surface,
CAIRO_OPERATOR_MULTIPLY is honored also for the second
highlight...</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> Tobias<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">On 03/11/2022 14:53, Tobias Hoffmann
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:a4f6fb9a-d16d-30b3-d483-846356c81b81@thax.hardliners.org">
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8">
<div class="moz-cite-prefix">
<div class="moz-cite-prefix">cairo 1.16.0 also exhibits the
problem.<br>
</div>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">AFAICT the difference between
"small" and "Virtual Mechanics" in the content stream (obj 4)
is that only for the "small" an additional "/b14 gs" command
is present:<br>
</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">[...]<br>
</div>
<div class="moz-cite-prefix">q<br>
106.926 93.812 33.621 13.883 re W n<br>
/b14 gs<br>
q<br>
1 0 0 1 106 93 cm<br>
/a0 gs /x7 Do<br>
Q<br>
Q q<br>
148.605 117.57 83.879 14.02 re W n<br>
q<br>
1 0 0 1 148 117 cm<br>
/a0 gs /x8 Do<br>
Q<br>
Q</div>
<div class="moz-cite-prefix">[...]</div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">The ExtGState definitions says:</div>
<div class="moz-cite-prefix">/a0 <<<br>
/CA 1<br>
/ca 1<br>
>></div>
<div class="moz-cite-prefix">/b14 <<<br>
/BM /Multiply<br>
>></div>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">Adding /b14 gs to drawing of the
second XObject (i.e. /x8) fixes the output.</div>
<div class="moz-cite-prefix"><br>
</div>
Maybe someone with more knowledge about cairo's pdf surface
and/or pdftocairo can help here?
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix"> Tobias<br>
</div>
<br>
<div class="moz-cite-prefix"><br>
</div>
<div class="moz-cite-prefix">On 03/11/2022 13:47, Beckmann Urs
(ID) wrote:<br>
</div>
<blockquote type="cite"
cite="mid:f46755f73b634df9bfd19577f0ae8b1e@id.ethz.ch">
<meta http-equiv="Content-Type" content="text/html;
charset=UTF-8">
<meta name="Generator" content="Microsoft Word 15 (filtered
medium)">
<style>@font-face
{font-family:"Cambria Math";
panose-1:2 4 5 3 5 4 6 3 2 4;}@font-face
{font-family:Calibri;
panose-1:2 15 5 2 2 2 4 3 2 4;}p.MsoNormal, li.MsoNormal, div.MsoNormal
{margin:0in;
font-size:11.0pt;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}span.EmailStyle17
{mso-style-type:personal-compose;
font-family:"Calibri",sans-serif;
color:windowtext;}.MsoChpDefault
{mso-style-type:export-only;
font-family:"Calibri",sans-serif;
mso-fareast-language:EN-US;}div.WordSection1
{page:WordSection1;}</style><!--[if gte mso 9]><xml>
<o:shapedefaults v:ext="edit" spidmax="1026" />
</xml><![endif]--><!--[if gte mso 9]><xml>
<o:shapelayout v:ext="edit">
<o:idmap v:ext="edit" data="1" />
</o:shapelayout></xml><![endif]-->
<div class="WordSection1">
<p class="MsoNormal"><span lang="EN-US">Dear Cairo
developers<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The attached pdf
small-sample-with-comments.pdf gives incorrect output
from pdftocairo -pdf.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">The yellow stripe
covers the text “Virtual Mechanics”, instead of being
transparent. Text “small” instead remains correctly not
covered after pdftocairo -pdf.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">pdftocairo -png and
pdftocairo -ps give correct results. It looks like the
problem comes from cairo pdf output engine.<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Tested with
cairo-version 1.17.4<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Kind regards<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US">Urs<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
</div>
</blockquote>
<p><br>
</p>
</blockquote>
<p><br>
</p>
</blockquote>
<p><br>
</p>
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