The rendering of a PDF file generated by LaTeX is unprecise, which leads to tiny holes in large parentheses as described here http://tex.stackexchange.com/q/115260. As this is reproducible in all tested poppler viewers including xpdf, but cannot be reproduces with mupdf, this seems to be a poppler issue. Unfortunately, I do not know poppler good enough to describe the problematic component, but it occurs in Okular, for example.
Where's the pdf file?
Created attachment 79645 [details]
Problematic PDF file
Sorry, for forgetting that. I just appended it (hole.pdf).
Just for clarity: The effect can only be seen with some zoom values (here for
example in Okular with 200% and 300% but not with 255%)
In case it is important:
Poppler version: 0.18.4
Works for me, or at least can you attach an image showing the problem?
Also you're using a version that is two major releases behind, so yes, obviously it matters
Created attachment 79652 [details]
Cropped problematic PDF
generated with pdfcrop (from Debian package: texlive-extra-utils)
Created attachment 79653 [details]
PNG converted from PDF
Created attachment 79654 [details]
Zoomed PNG file (converted from PDF)
The red highlighting of the problematic areas has been done manually
I created a cropped variant of the PDF file (without the page number), to focus on the problem at hand ("Cropped problematic PDF").
I checked out the git version of poppler to confirm, that the problem still exists. As I don't have a viewer capable of handling the most recent poppler version, I used the "pdftocairo" tool to generate a PNG file from the PDF file with the following command:
./pdftocairo -r 170 -png hole-crop.pdf ~hole-crop
This lead to the attachment "PNG converted from PDF". To highlight the problem, I marked the problematic areas with red color and zoomed-in, which can be seen in "Zoomed PNG file (converted from PDF)".
The problem seems to be more obvious in Okular (but this might be due to the older poppler version): http://tex.stackexchange.com/q/115260
I hope you can reproduce the problem with the above instructions. Please note, that the resolution option in the "pdftocairo" command is very critical. I did not see the problem for "-r 171", for example.
Okular and pdftocairo use different renderers, can you please see if you can reproduce with pdftoppm too (which uses the same renderer as Okular)?
Created attachment 79655 [details]
Generated with 'pdftoppm -r 94'
Created attachment 79656 [details]
Generated with 'pdftoppm -r 154'
Created attachment 79657 [details]
Generated with 'pdftoppm -r 154' with poppler 0.18.4
Yes, the problem can also be seen with pdftoppm ("Generated with 'pdftoppm -r 94'" and "Generated with 'pdftoppm -r 154'"). You possibly have to zoom-in to detect it.
With recent poppler versions the problem seems to be less critical and occurs only for a small number of low-resolutions. With poppler 1.18.4, the problem is more severe ("Generated with 'pdftoppm -r 154' with poppler 0.18.4") and also occurs for higher resolutions.
Created attachment 80083 [details]
Another example of imperfections
Hi guys, I can confirm this problem. I added file "Curly brackets and square root" where you can find other imperfections. Maybe you need to try different levels of zoom to see them. Pdf has been generated with pdflatex and does not show these defects with Adobe Reader.
Yes, I probably forgot to mention, the problem can always happen when two line/curve segments are placed next to each other.
@Marco, thanks for the additional information. It would be good if you could add information about the viewer you used (okular?), which poppler version is installed and at which zoom levels the problem can be seen (maybe even with screen shots).
One hint: You should set the MIME-Type of the uploaded files correctly, e.g. application/pdf instead of text/plain for a PDF file.
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