Make a Thicker Latin Modern Roman

All free fonts with unicode-math support are imperfect. To my taste, Latin Modern is the most polished free OTF font with unicode math, except for its thin and sharp strokes and the lack of lowercase script math. I spent some hobby time trying to figure out how to automatically create a thicker version of the font.

Date of posting: 2019-11-02
Last modification: 2020-02-11

The following fonts are the available ones with unicode-math support on my operating system:

- XITS Math
- STIX Two Math
- Asana Math
- TeX Gyre Bonum Math
- TeX Gyre Pagella Math
- TeX Gyre Schola Math
- TeX Gyre Termes Math
- TeX Gyre DejaVu Math
- Latin Modern Math
- Libertinus Math
- Garamond Math
- Cambria Math

- Both STIX version 1 and 2 are beautiful fonts for the text part, however
- XITS/STIX1 do not distinguish bold and regular uppercase letters obviously.
- STIX Two is not mature enough. Especially, the math font has misaligned accents. Besides it contains a few annoying mistakes which require special tricks to amend.

- Schola and Termes has the same non-optimal kerning for mixed italic and
upright styles. For example, both much too less space before a bold
italic
`j`

. - Pagella has comfortable kernings, but the difference between bold
and regular styles of
`v`

and`w`

is not obvious. - I did not try Bonum for documents. Its glyphs are slightly wider than the others and may cause overfull boxes, especially when it is used in A5 pages.
- The strokes in Latin Modern/Computer Modern fonts are too thin for screens and laser printers. (Though the original CMR could be acceptable, if one could perform a few tests on the target printer, but still not optimal for screen reading.)

`blacker`

value to
make the glyphs thicker. However, the texts are rendered as if they were
misaligned, even with a high rasterizing DPI. Besides, who would use a bitmap
font nowadays?
The fake bold works in both XeLaTeX and LuaLaTeX. In XeLaTeX it is written as

\setmainfont[% FakeBold=1, SmallCapsFont={* Caps}, SlantedFont={* Slanted}, ]{Latin Modern Roman}and for the current LuaLaTeX (works in XeLaTeX as well)

\setmainfont[% RawFeature={embolden=1.0} SmallCapsFont={* Caps}, SlantedFont={* Slanted}, ]{Latin Modern Roman}A fakebold factor of 1.0 as in the above settings makes the document looking quite nice in Adobe Reader, SumatraPDF and in the Firefox browser, too. However, the visual effect depends on the PDF reader. Okular renders fakebolds imperfectly, but still acceptable; while the current evince or other readers based on poppler cairo will make the font much bolder (full bold).

(my doc folder)$ tree fakebold/ fakebold/ ├── adjust-lm.sh ├── adjust-lm-stroke.pe ├── adjust-lm-weight.pe └── origin ├── latinmodern-math.otf ├── lmroman10-bolditalic.otf ├── lmroman10-bold.otf ├── lmroman10-italic.otf ├── lmroman10-regular.otf ├── lmroman12-bold.otf ├── lmroman12-italic.otf ├── lmroman12-regular.otf ├── lmroman17-regular.otf ├── lmroman5-bold.otf ├── lmroman5-regular.otf ├── lmroman6-bold.otf ├── lmroman6-regular.otf ├── lmroman7-bold.otf ├── lmroman7-italic.otf ├── lmroman7-regular.otf ├── lmroman8-bold.otf ├── lmroman8-italic.otf ├── lmroman8-regular.otf ├── lmroman9-bold.otf ├── lmroman9-italic.otf ├── lmroman9-regular.otf ├── lmromancaps10-oblique.otf ├── lmromancaps10-regular.otf ├── lmromandunh10-oblique.otf ├── lmromandunh10-regular.otf ├── lmromanslant10-bold.otf ├── lmromanslant10-regular.otf ├── lmromanslant12-regular.otf ├── lmromanslant17-regular.otf ├── lmromanslant8-regular.otf ├── lmromanslant9-regular.otf └── lmromanunsl10-regular.otf 1 directory, 37 filesAlthough the Python API of fontforge exposures more features than the native script language, those additional features will not be needed here. In addition, the advantage of the native script is that the work can be easily parallelized by launching a shell process for each OTF file as you will see later.

`ChangeWeight()`

of fontforge. After the
weight is enlarged, each glyph becomes slightly wider. Therefore, a rescaling
is worth to be considered. Only horizontal shrinking is applied here since
vertical scaling will misalign the baselines.
There are two caveats:

- Simplifying the glyphs before scaling, otherwise the shapes of some
symbols will be destroyed, as visualized in Fig.1a-1c.
- Some glyphs have distorted shapes after changing the weight, as shown in the Fig.2. The solution is to split the increasing of weight into sub-steps accumulatively.

`adjust-lm-weight.pe`

for this approach is
1 #!/user/bin/fontforge 2 3 Open("origin/"+$1) 4 SelectAll() 5 Simplify() 6 i = 0 7 while(i < Strtol($2)) 8 ChangeWeight(Strtod($3)) 9 ++i 10 endloop 11 if($4 == "true") 12 Scale(95, 100) 13 endif 14 RemoveOverlap() 15 RemoveHints() 16 Generate($1) 17 Close()and

`adjust-lm-weight.sh`

is:
1 #!/bin/sh 2 3 for i in origin/lmroman*.otf ; do 4 fontforge adjust-lm.pe "${i#origin/}" 3 5.0 true & 5 done 6 7 fontforge adjust-lm.pe latinmodern-math.otf 1 15.0 false & 8 9 wait

The script `adjust-lm-stroke.pe`

is now

1 #!/user/bin/fontforge 2 3 Open("origin/"+$1) 4 SelectAll() 5 joinstyle = 0 6 i = 0 7 while (i < Strtod($2)) 8 ExpandStroke(Strtol($3), 1, joinstyle, 0, 1) 9 ++i 10 endloop 11 RemoveOverlap() 12 ClearHints() 13 Simplify() 14 RoundToInt() 15 Generate($1) 16 Close()and

`adjust-lm-weight.sh`

:
1 #!/bin/sh 2 for i in origin/lmroman*.otf ; do 3 fontforge adjust-lm-stroke.pe "${i#origin/}" 3 6 & 4 done 5 # \symscr{L} would have problem with 3*6, switch to 1*18 for math 6 fontforge adjust-lm-stroke.pe latinmodern-math.otf 1 18 & 7 waitHints should be removed, as the original ones are no more optimal and

`AutoHint()`

from fontforge is not clever enough.
1 % Extract the fonts in 'fakebold/' 2 \usepackage{fontspec} 3 \usepackage[warnings-off={mathtools-colon,mathtools-overbracket}]{unicode-math} 4 \setmainfont[% 5 Path={fakebold/}, 6 % 7 UprightFont={*-regular.otf}, 8 UprightFeatures={% 9 SmallCapsFont={lmromancaps10-regular.otf}, 10 SizeFeatures={% 11 {Size= -5.5, Font={lmroman5-regular.otf}},% 12 {Size= 5.5-6.5, Font={lmroman6-regular.otf}},% 13 {Size= 6.5-7.5, Font={lmroman7-regular.otf}},% 14 {Size= 7.5-8.5, Font={lmroman8-regular.otf}},% 15 {Size= 8.5-9.5, Font={lmroman9-regular.otf}},% 16 {Size= 9.5-11.5, Font={lmroman10-regular.otf}},% 17 {Size= 11.5-14.5, Font={lmroman12-regular.otf}},% 18 {Size= 14.5- , Font={lmroman17-regular.otf}}% 19 }% 20 },% 21 % 22 BoldFont={lmroman10-bold.otf}, 23 BoldFeatures={% 24 SizeFeatures={% 25 {Size= -5.5, Font={lmroman5-bold.otf}},% 26 {Size= 5.5-6.5, Font={lmroman6-bold.otf}},% 27 {Size= 6.5-7.5, Font={lmroman7-bold.otf}},% 28 {Size= 7.5-8.5, Font={lmroman8-bold.otf}},% 29 {Size= 8.5-9.5, Font={lmroman9-bold.otf}},% 30 {Size= 9.5-11.5, Font={lmroman10-bold.otf}},% 31 {Size= 11.5- , Font={lmroman12-bold.otf}},% 32 }% 33 },% 34 % 35 ItalicFont={lmroman10-italic.otf}, 36 ItalicFeatures={% 37 SizeFeatures={% 38 {Size= -7.5, Font={lmroman7-italic.otf}},% 39 {Size= 7.5-8.5, Font={lmroman8-italic.otf}},% 40 {Size= 8.5-9.5, Font={lmroman9-italic.otf}},% 41 {Size= 9.5-11.5, Font={lmroman10-italic.otf}},% 42 {Size= 11.5- , Font={lmroman12-italic.otf}}% 43 }% 44 },% 45 BoldItalicFont={lmroman10-bolditalic.otf},% 46 % 47 SlantedFont={lmromanslant10-regular.otf}, 48 SlantedFeatures={% 49 SmallCapsFont={lmromancaps10-oblique.otf}, 50 SizeFeatures={% 51 {Size= -8.5, Font={lmromanslant8-regular.otf}},% 52 {Size= 8.5-9.5, Font={lmromanslant9-regular.otf}},% 53 {Size= 9.5-11.5, Font={lmromanslant10-regular.otf}},% 54 {Size= 11.5-14.5, Font={lmromanslant12-regular.otf}},% 55 {Size= 14.5- , Font={lmromanslant17-regular.otf}}% 56 }% 57 },% 58 BoldSlantedFont={lmromanslant10-bold.otf},% 59 % 60 Ligatures={TeX} 61 ]{lmroman10}% 62 \newfontfamily\upit[Path={fakebold/}]{lmromanunsl10-regular.otf} 63 \newcommand{\textupit}[1]{{\upit#1}} 64 \newcommand{\textitup}[1]{{\upit#1}} 65 \newfontfamily\dhstyle[Path={fakebold/},Scale=MatchLowercase,UprightFont={*-regular.otf},SlantedFont={*-oblique.otf}]{lmromandunh10} 66 \newcommand{\textdh}[1]{{\dhstyle#1}} 67 % 68 \setsansfont[% 69 Scale=MatchUppercase, 70 Ligatures=TeX 71 ]{Latin Modern Sans} 72 \newfontfamily{\dcstyle}[% 73 ItalicFont={lmsansdemicond10-oblique.otf},% 74 SlantedFont={lmsansdemicond10-oblique.otf},% 75 ]{lmsansdemicond10-regular.otf} 76 \newcommand{\textdc}[1]{{\dcstyle#1}} 77 % 78 \setmonofont[% 79 Scale=MatchUppercase 80 ]{Latin Modern Mono} 81 % 82 \setmathfont[% 83 Path={fakebold/}, 84 bold-style=ISO, 85 partial=upright 86 ]{latinmodern-math.otf} 87 % 88 \setmathfontface\symupit[% 89 Path={fakebold/}, 90 ]{lmromanunsl10-regular.otf} 91 % 92 \setmathfontface\symitup[% 93 Path={fakebold/}, 94 ]{lmromanunsl10-regular.otf}

- No hints, but this is with the modern PDF renders no more a critical problem.
- Sans Serif Math symbols are improperly thicker (but acceptable).
~~Fraktur letters become improperly thicker~~(fixed in the recent version).- The thickness of LM Sans and other fonts have to be rematched (but acceptable by default).

- thick-lm-otf.zip usage see the settings above
- thick-lm-pfb.zip
extract the files to
`~/texmf/fonts/type1/public/lm/`

*Edit 2020-02-21:* update download link, update sample TeX settings.