groffhl is a small program for converting Linux "truecolor" escape sequences into native groff format. You can then take the output and paste it into another groff document.

groffhl intakes a file with colors encoded as 24-bit "truecolor" escape sequences (e.g. \033[38;2;255;0;0m *red* \033[m). It scans the whole file, remembers every distinct color and substitutes it to groff format (e.g. \m[red] *red* \m[]) and finally prints a header including all color declarations, followed by the formatted code.

Let's say we want to colorize this code snippet in groff:

1. First, we need it as a plaintext file, let's call it "hello.c".
2. Next we can use a tool like highlight to do the highlighting:

3. Next, we feed this new "highlighted.txt" file to groffhl:

$ groffhl highlighted.txt >highlighted.groff

The resulting highlighted.groff file looks like this:

.defcolor groffhl_0 rgb 0.058824f 0.576471f 0.058824f
.defcolor groffhl_1 rgb 0.325490f 0.988235f 0.988235f
.defcolor groffhl_2 rgb 0.411765f 0.780392f 0.537255f
.defcolor groffhl_3 rgb 1.000000f 1.000000f 1.000000f
.defcolor groffhl_4 rgb 0.776471f 0.254902f 0.776471f
.defcolor groffhl_5 rgb 0.972549f 0.819608f 0.819608f
.defcolor groffhl_6 rgb 0.815686f 0.815686f 0.270588f
.defcolor groffhl_7 rgb 0.901961f 0.298039f 0.901961f

\m[groffhl_0]\m[]\m[groffhl_1]#include <stdio.h>\m[]
\m[groffhl_0]\m[]
\m[groffhl_0]\m[]\m[groffhl_2]int\m[] \m[groffhl_0]\m[]\m[groffhl_3]main\m[]\m[groffhl_0]\m[]\m[groffhl_3](\m[]\m[groffhl_0]\m[]\m[groffhl_2]int\m[] \m[groffhl_0]argc\m[]\m[groffhl_3],\m[] \m[groffhl_0]\m[]\m[groffhl_2]char\m[] \m[groffhl_0]\m[]\m[groffhl_3]**\m[]\m[groffhl_0]argv\m[]\m[groffhl_3])\m[]
\m[groffhl_0]\m[]\m[groffhl_3]{\m[]
\m[groffhl_0]\m[]    \m[groffhl_3]printf\m[]\m[groffhl_0]\m[]\m[groffhl_3](\m[]\m[groffhl_0]\m[]\m[groffhl_4]"Hello, world!\m[]\m[groffhl_5]\en\m[]\m[groffhl_4]"\m[]\m[groffhl_0]\m[]\m[groffhl_3]);\m[]
\m[groffhl_0]\m[]    \m[groffhl_6]return\m[] \m[groffhl_0]\m[]\m[groffhl_7]0\m[]\m[groffhl_0]\m[]\m[groffhl_3];\m[]
\m[groffhl_0]\m[]\m[groffhl_3]}\m[]\m[groffhl_0]\m[]

As you can see, groffhl keeps track of all colors and neatly organizes them in a simple declaration block. Also, be wary that highlight produces output intended for terminal emulators which typically have a black background. Meanwhile, groff documents tend to print text on white pages, so you will likely need to tweak some of the color definitions to suit your needs. For example, in the above file you'll notice that groffhl_3 has an RGB value of (1, 1, 1), which is pitch white. On a white page, all code written in this color would appear invisible, so usually you want to change it manually to black instead.

Here is the final result, after a few small manual tweaks to the color definitions:

Arch Linux users can install the groffhl-git package from the AUR.

Clone the repo and run the following (if necessary, as root):

make install

The executable will be installed to /usr/local/bin/groffhl.

You can uninstall in the same way with

make uninstall

• Support for bold/italic sequences (\033[1;38;2;r;g;bm, \033[3;38;2;r;g;bm)
• Ignoring unsupported sequences (see full list here)
• man page