[Tex/LaTex] Blackboard Bold i

amsmathmath-modemathbbpackagessymbols

Although it is not standard notation, I quite like the fact that in Mathematica, a blackboard bold i is used to represent the imaginary unit. Apart from making it stick out, it allows me to write things such as

enter image description here,

allowing me to use the variable 'i' as an iterator in series, etc. To achieve this in LaTeX, I've made use of the bbm package (\mathbbm i), however this doesn't render as nicely as the standard AMS math \mathbb command, in fact, it looks pixellated up close:

enter image description here

Is there a way to achieve a nicer blackboard bold i symbol? I'm not very fond of what is offered by the packages bbold, mathbbol or dsfont packages either, I want to get something as close to AMS's \mathbb as possible.

Best Answer

Here, I use dafrick's answer at Double-struck zero and one to use the boondox-ds versions of bb fonts, designated here as \mymathbb{}. I used j in one location so that you can see it is not pixelated.

The fonts are installed via the boondox-dx package, which is not invoked below, so as not to overwrite the native \mathbb implementation otherwise available through amssymb.

\documentclass{article}
\usepackage{amsmath}
\DeclareMathAlphabet{\mymathbb}{U}{BOONDOX-ds}{m}{n}
\begin{document}
    \[
      x_i(t) = \mathop{\mathrm{Re}}(A_i e^{8000\pi\mymathbb{j}t}c^{\phi_i\mymathbb{i}}) \text{for $i = 1, 2, 3$}
    \]
\end{document}

enter image description here

FOLLOW UP

In comments, the OP asks for the \mathbb{i} from TG Pagella Math (OpenType format), but for use in pdflatex, which is not available. Since it is only a single glyph that is being requested, here is a kludge to obtain it:

Create the document TGbbi.tex as follows, and compile in Xelatex:

\documentclass{standalone}
\usepackage{unicode-math}
\setmathfont{TeX Gyre Pagella Math}
\begin{document}
$\mathbb{i}$
\end{document}

It creates the output TGbbi.pdf containing only the Pagella version of \mathbb{i}. Now, reverting back to pdflatex, we are going to call upon that graphic for use in a macro named \bbi defined as

\newcommand\bbi{\ThisStyle{%
  \setbox0=\hbox{$\SavedStyle\mathbb{i}$}\includegraphics[height=\ht0]{TGbbi}}}

This macro requires the graphicx package (to import the graphic) and the scalerel package (to auto-scale it to the proper math size, taken as the vertical height of the regular \mathbb{i}). Thus, the implementation (showing use in several different math sizes) is

\documentclass{article}
\usepackage{amssymb,amsmath,scalerel,graphicx}
\newcommand\bbi{\ThisStyle{%
  \setbox0=\hbox{$\SavedStyle\mathbb{i}$}\includegraphics[height=\ht0]{TGbbi}}}
\begin{document}
    \[
      x_i(t) = \mathop{\bbi\mathrm{Re}}(A_i e^{8000\pi\bbi t}c^{\phi_i\bbi}) \text{for $i = 1, 2, 3$}
    \]
\end{document}

enter image description here

Zoom:

enter image description here

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