[Tex/LaTex] How to change font for the integral symbol

math-modesymbols

I'm looking how to change the integral symbol.

For example:

\documentclass{article}
\begin{document}
\[\int_a^b f(x) \mathrm{d} dx\]
\end{document}

I want to only change the font of \int to get a \rm\int like \mathrm{d} or can I define a new \rmint using other package, for example arev?

\documentclass{article}
 %define a new command for \rm font of int

\begin{document}
\[\rmint_a^b \]
\end{document}

to get the style of \int is

enter image description here

I have get \rmoint and \rmint by

\DeclareMathSymbol{\rmintop}{\mathop}{rmlargesymbols}{82}
\DeclareMathSymbol{\rmointop}{\mathop}{rmlargesymbols}{72}

but I can not get all of integrals as follows:

enter image description here

Best Answer

Define a new math font from a new font family besides the default cmex, for instance, mdbch and euex. Refer to arevmath.sty.

\documentclass{article}
%define a new command for \rm font of int
\DeclareSymbolFont{rmlargesymbols}{OMX}{mdbch}{m}{n}
% or \DeclareSymbolFont{rmlargesymbols}{U}{euex}{m}{n}
\DeclareMathSymbol{\rmintop}{\mathop}{rmlargesymbols}{82}
\newcommand{\rmint}{\rmintop\nolimits}
\begin{document}
$\rmint_a^b$
\[\rmint_a^b \]

\end{document}
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