[SOLVED] Terrible PDF font kerning

[mfdeakin]

Hi,

Many (but not all; ones produced by TeX look fine) PDFs have terrible font kerning issues in multiple pdf renderers (qpdfview and Chromium's pdf reader produce identical results) for me. See the following image for an example http://i.imgur.com/kY5gSad.png
I've had this issue for years, and failed to find a solution in my previous searches, as similar issues don't seem to be the same (they're either not as bad or bad differently).
Have any of you seen something similar to this or had instructions on how to fix this?

Here's my configure options for poppler:
[ebuild R ~] app-text/poppler-0.52.0:0/66::gentoo USE="cairo cxx introspection jpeg jpeg2k lcms png qt4 tiff utils -cjk -curl -debug -doc -nss -qt5" 0 KiB

In case it's relevant, here's eselect fontconfig list:
Available fontconfig .conf files (* is enabled):
[1] 09-texlive.conf
[2] 10-autohint.conf
[3] 10-no-sub-pixel.conf
[4] 10-scale-bitmap-fonts.conf
[5] 10-sub-pixel-bgr.conf
[6] 10-sub-pixel-rgb.conf
[7] 10-sub-pixel-vbgr.conf
[8] 10-sub-pixel-vrgb.conf
[9] 10-unhinted.conf
[10] 11-lcdfilter-default.conf
[11] 11-lcdfilter-legacy.conf
[12] 11-lcdfilter-light.conf
[13] 20-unhint-small-vera.conf
[14] 25-unhint-nonlatin.conf
[15] 30-metric-aliases.conf
[16] 30-urw-aliases.conf
[17] 40-nonlatin.conf
[18] 45-latin.conf
[19] 49-sansserif.conf
[20] 50-user.conf
[21] 51-local.conf
[22] 59-google-droid-sans-mono.conf *
[23] 59-google-droid-sans.conf *
[24] 59-google-droid-serif.conf *
[25] 60-latin.conf
[26] 60-liberation.conf
[27] 61-stix.conf
[28] 65-fonts-persian.conf
[29] 65-khmer.conf
[30] 65-nonlatin.conf
[31] 69-unifont.conf
[32] 70-no-bitmaps.conf
[33] 70-yes-bitmaps.conf
[34] 75-yes-terminus.conf
[35] 80-delicious.conf
[36] 90-synthetic.conf
[37] 99pdftoopvp.conf


Thanks in advance

[ct85711]

From what I am understanding, the are complaining about the ligatures, explained and shown here:
http://tex.stackexchange.com/questions/297426/spacing-between-letters-ligature

This post explains more on how to work around/disable it some.
http://tex.stackexchange.com/questions/1841/how-can-i-completely-suppress-ligatures

If I am misunderstanding, please explain (and maybe an image) pointing the what the issue is.

[mfdeakin]

[Fitzcarraldo]

mfdeakin,

Fonts confuse me. If I understand you correctly, your problem is at the creation stage rather than the rendering stage. It's probably not relevant in your case, but I was seeing something a bit like your problem when I use Microsoft Word 2007 under WINE in Gentoo and saved my files to PDF; when the document contained 'smart quotes' (curly quotes) the kerning of the line was messed up badly. Once I changed the quotes in the documents to 'straight quotes' it resolved the problem. What I was having a lot of trouble with on my Compal NBLB2 laptop was the quality of the rendering of the font -- rather than its kerning -- which I resolved by remerging media-libs/freetype with the USE flag selection shown below and changing to the Infinality fonts:

[Ant P.]

That looks nasty. It looks like it's switching between fonts in the middle of the sentence but using the metrics from only one of them? In Chromium you should be able to right click and open the PDF in the dev console to see which fonts it's trying to use, that might help to see what's wrong.

[mfdeakin]

The PDF I took a picture of was using the Roboto medium and regular fonts, if I understand chromium's dev console correctly. I don't have the roboto font package installed, so I assume I do understand and that it's using the version embedded in the PDF.
I should also note that while I'm not certain what the cause of the problem is, it appears that it might be font specific, as some text in the PDF is not mangled.
I don't think it's fair to say the issue is with the creation of the PDF, as these PDFs render normally on any other computer or OS.

Here is some more information on possibly relevant packages:

[khayyam]

[mfdeakin]

khayyam, replacing the fonts did fix my issue in this PDF, so it is a font substitution problem! Thanks! How would I fix this in a more permanent manner? I've tried changing what's available in 'eselect fontconfig', but that didn't seem to fix the issue in the past. Installing the roboto font does fix it for this font, but I'd rather not have to install all of the fonts to fix this permanently.

[khayyam]

[Ant P.]

The roboto font itself is pretty badly kerned, that's probably contributing to the problem here. Unfortunately it looks like all good-looking versions of it (version numbers were YYYY.MM) have been removed from the tree...

[mfdeakin]

Enabling '30-metric-aliases.conf' did fix my issue even after uninstalling the (frankly bad as Ant mentioned) Roboto font; at least for this PDF. Thanks for the help!

[khayyam]