It looks like OP is already doing that. Or rather, OP calls katex (https://katex.org/ https://katex.org/) to get MathML and HTML; then renders the HTML to a ras

It looks like OP is already doing that. Or rather, OP calls katex (https://katex.org/ https://katex.org/) to get MathML and HTML; then renders the HTML to a raster image. But he's throwing the MathML away.