How to change the font colour on the slide with background image in quarto pptx?

[udurraniAtPresage]

Description

I have blue and black colours for my slide title and body fonts. How do I change these colours for only that slide where I have a background image?

The qmd includes:

---
title: "Title"
subtitle: "subtitle."
format:
  pptx:
    reference-doc: template.pptx
    incremental: true   
---

## Slide with background image {background-image="william-hook-Wtn654UyGYA-unsplash.jpg"}

I am a [red]{style="color:green;"} word.

This produces the following result:

[mcanouil]

You need to use OpenXML inline raw block.
[red]{style="color:green;"} has no meaning in Quarto (or Pandoc) outside of HTML based formats.

See:

• https://quarto.org/docs/authoring/markdown-basics.html#raw-content
• https://quarto.org/docs/authoring/markdown-basics.html#sec-divs-and-spans (these could be used with a Lua filter for example, Inline Font color with {.class} are not correctly rendered in epub and pdf #5300 (reply in thread))

[mcanouil]

I edited (quick & dirty) to include the OpenXML code:

Span = function(span)
  color = span.attributes['color']
  if color == nil then return span end

  if FORMAT:match 'html' or FORMAT:match 'revealjs' then
    span.attributes['color'] = nil
    span.attributes['style'] = 'color: ' .. color .. ';'
    return span
  elseif FORMAT:match 'latex' or FORMAT:match 'beamer' then
    span.attributes['color'] = nil
    if string.sub(color, 1, 1) == "#" and #color == 7 then
      -- TODO: requires xcolor
      local R = tostring(tonumber(string.sub(color, 2, 3), 16))
      local G = tostring(tonumber(string.sub(color, 4, 5), 16))
      local B = tostring(tonumber(string.sub(color, 6, 7), 16))
      table.insert(
        span.content, 1,
        pandoc.RawInline('latex', '\\textcolor[RGB]{'..R..','..G..','..B..'}{')
      )
    elseif string.sub(color, 1, 1) == "#" and #color == 4 then
      -- TODO: requires xcolor
      local R = tostring(tonumber(string.sub(color, 2, 2), 16) * 0x11)
      local G = tostring(tonumber(string.sub(color, 3, 3), 16) * 0x11)
      local B = tostring(tonumber(string.sub(color, 4, 4), 16) * 0x11)
      table.insert(
        span.content, 1,
        pandoc.RawInline('latex', '\\textcolor[RGB]{'..R..','..G..','..B..'}{')
      )
    else
      table.insert(
        span.content, 1,
        pandoc.RawInline('latex', '\\textcolor{'..color..'}{')
      )
    end
    table.insert(
      span.content,
      pandoc.RawInline('latex', '}')
    )
    -- returns only span content
    return span.content
  elseif FORMAT:match 'docx' or FORMAT:match 'pptx' then
    span.attributes['color'] = nil
    table.insert(
      span.content, 1,
      pandoc.RawInline('openxml', '<w:r><w:rPr><w:color w:val="' .. color:gsub("^#", "") .. '"/></w:rPr><w:t>')
    )
    table.insert(
      span.content,
      pandoc.RawInline('openxml', '</w:t></w:r>')
    )
    return span.content
  else
    -- for other format return unchanged
    return span
  end
end

---
format: docx
filters:
  - colour.lua
---

`<w:r><w:rPr><w:color w:val="FF0000"/></w:rPr><w:t>Red Text</w:t></w:r>`{=openxml}

[Green Text]{color=00FF00}

[Blue Text]{color=#0000FF}

[cscheid]

@gordonwoodhull (not a request for us to do it!) This is the beginning of the same technique we use in typst, but aimed at docx...

[udurraniAtPresage]

Whoa! That's awesome.

[mcanouil]

Quite early, but here is an extension:

• https://github.com/mcanouil/quarto-highlight-text