“Remapping” a single glyph

Question

I am using the excellent Heuristica typeface, but I don't like the way the old style "1" looks. It looks more like an "I" in small caps than an actual number, unlike the Adobe original. Like so:

Is there a way to remap this single character to use a different font, or a not incredibly painful way to edit the font itself? (since I'm using the text figures for section numberings and the like, I would prefer a document wide solution)

EDIT: Minimal working example:

\documentclass[letterpaper,12pt]{amsart}

\usepackage[osf,scaled=.92]{heuristica}

\begin{document}
  012782
\end{document}

Answer 1

I've found some inspiration in the XeTeX reference guide (Character Classes, pages 14 and 15) and in these Q+A, Font substitution with XeLaTeX and Replacing "a" in latin modern. This is my try. I've installed http://www.ctan.org/tex-archive/fonts/heuristica by unzipping+copying files into my TeX distribution's local directory followed by mktexlsr and I am using the OTF file directly. I am using scaling of 0.86, 0.92 didn't look right.

By the way, I like the approach with \xeCJKDeclareSubCJKBlock from xeCJK package, but it's adding some extra spaces before and after digit 1, so please find it among the commented lines. There is an extended example of using this method, Combining Chinese, Japanese and Korean text with xeCJK.

% run: xelatex mal-one.tex
\documentclass[letterpaper,12pt]{article}%amsart
\pagestyle{empty}
% There are some extra spaces before and after "1", but it works...
%\usepackage{xeCJK}
%\xeCJKDeclareSubCJKBlock{one}{"0031}
%\setmainfont[Scale=0.92,RawFeature=+onum]{Heuristica-Regular.otf}
%\setCJKmainfont[one,Scale=0.86,RawFeature=-onum]{Heuristica-Regular.otf}
%\ifx
\usepackage{fontspec}
\setmainfont[RawFeature=+onum,Scale=0.92]{Heuristica-Regular.otf}
\newfontfamily{\mfont}[RawFeature=-onum,Scale=0.86]{Heuristica-Regular.otf}
\XeTeXinterchartokenstate=1
\newXeTeXintercharclass\msub
\XeTeXcharclass"0031=\msub
\XeTeXinterchartoks 0 \msub = {\begingroup\mfont}
\XeTeXinterchartoks 255 \msub = {\begingroup\mfont}
\XeTeXinterchartoks \msub 0 = {\endgroup}
\XeTeXinterchartoks \msub 255 = {\endgroup}
%\fi
\begin{document}
  012782
\end{document}

---

Next option would be to use mapping file (teckit_compile). I enclose the mapping file (mal-one-bonus.map) which is first processed by:

teckit_compile -o mal-one-bonus.tec mal-one-bonus.map

Instead of activating +onum we defined own character mapping. The source code is:

; This is mal-one-bonus.map file...
LHSName "input"
RHSName "output"
pass(Unicode)
UniClass [inputs] = (U+0030 U+0032..U+0039)
UniClass [outputs] = (U+F643 U+F645..U+F64C)
[inputs] <> [outputs]

Then we run xelatex mal-one-a.tex (it doesn't work with lualatex):

% run: xelatex mal-one-a.tex
\documentclass[letterpaper,12pt]{article}%amsart
\pagestyle{empty}
\usepackage{fontspec}
\setmainfont[Scale=0.92,Mapping=mal-one-bonus]{Heuristica-Regular.otf}
% RawFeature=+onum,
\begin{document}
  012782
\end{document}

---

I am thinking if a ligature (FeatureFile) could be used to solve this problem in lualatex. This is it, a new feature file (mal-feature.fea):

languagesystem DFLT dflt;
languagesystem latn dflt;
# A new ligature...
feature liga {
  sub one.taboldstyle by one;
  } liga;

We active it by lualatex mal-one-b.tex (it doesn't work with xelatex):

% run: lualatex mal-one-b.tex
\documentclass[letterpaper,12pt]{article}%amsart
\pagestyle{empty}
\usepackage{fontspec}
\usepackage{luatextra}
\setmainfont[Scale=0.92,FeatureFile=mal-feature.fea,RawFeature=+liga;+onum]{Heuristica-Regular.otf}
\begin{document}
  012782
\end{document}

Answer 2

Following cfr's suggestion I edited the Type 1 binaries in FontForge to make the OSF look more like the lining figures. Here's what my final result looks like:

This shows both the virtues (consistency with fractions and superior figures) and the vices — poor spacing in numbers like 2011, although it was that way in the original also.

Heuristica is licensed under the OFL so my modified version should be okay to share in case someone from the future wants it. The only caveat is that the modified version can't be called "Heuristica" anymore. At least that's my interpretation of the license, and I welcome corrections.