Inline codes are not highlighted after using "knit html" function in Rstudio - html

Question

I wrote an .Rmd file with some inline codes quoted by "`", and I used the knit html function in Rstudio to convert the .Rmd file to .html. However, the inline codes were not highlighted as on stackoverflow, and I took a look at the source codes of the .html file and found that the setting was like
tt, code, pre {
font-family: 'DejaVu Sans Mono', 'Droid Sans Mono', 'Lucida Console', Consolas, Monaco, monospace;
}
And I tried altering this block:
tt, code, pre {
font-family: 'DejaVu Sans Mono', 'Droid Sans Mono', 'Lucida Console', Consolas, Monaco, monospace;
background-color: #F8F8F8;
}
And it worked.
However, I do not want to do such work every time after I knit the .Rmd file to .html. I have read the help files of knit2html and markdownHTMLOptions in R but found no solution. Is there any solution to this issue?

Answer 1

With the latest version of the markdown package on CRAN, you can use the header argument to add additional CSS code to the HTML output, e.g.
library(knitr)
knit2html(...,
header = c('<style type="text/css">', 'code{background-color: #F8F8F8;}', '</style>'))
Or just set this as a global option in your ~/.Rprofile:
options(markdown.HTML.header = c('<style type="text/css">', 'code{background-color: #F8F8F8;}', '</style>'))
And the markdown package will use it every time when you simply run knit2html() without explicitly specifying the header argument.
With RStudio, it is a little trickier. See the documentation Customizing Markdown Rendering.