use lightened colors for brand background colors

fixes #11485

Author: gordonwoodhull

src/resources/filters/quarto-post/typst-brand-yaml.lua

@@ -70,11 +70,6 @@ function render_typst_brand_yaml()
           end
           local decl = '#let brand-color = ' .. to_typst_dict_indent(colors)
           quarto.doc.include_text('in-header', decl)
-          local BACKGROUND_OPACITY = 0.1
-          local themebk = {}
-          for name, _ in pairs(brandColor) do
-            themebk[name] = _quarto.modules.brand.get_background_color(name, BACKGROUND_OPACITY)
-          end
           if brandColor.background then
             quarto.doc.include_text('in-header', '#set page(fill: brand-color.background)')
           end
@@ -84,7 +79,11 @@ function render_typst_brand_yaml()
             quarto.doc.include_text('in-header', '#set line(stroke: (paint: brand-color.foreground))')
 
           end
-          local decl = '// theme colors at opacity ' .. BACKGROUND_OPACITY .. '\n#let brand-color-background = ' .. to_typst_dict_indent(themebk)
+          local themebk = {}
+          for name, _ in pairs(brandColor) do
+            themebk[name] = 'brand-color.' .. name .. '.lighten(85%)'
+          end
+          local decl = '#let brand-color-background = ' .. to_typst_dict_indent(themebk)
           quarto.doc.include_text('in-header', decl)
         end
         local function conditional_entry(key, value, quote_strings)

tests/docs/smoke-all/typst/brand-yaml/color/posit/brand-color.qmd

@@ -10,7 +10,7 @@ _quarto:
         -
           - 'burgundy: rgb\("#9a4665"\),'
           - 'primary: rgb\("#447099"\),'
-          - 'primary: rgb\("#44709919"\),' # background
+          - 'primary: brand-color\.primary\.lighten\(85%\),'
           - 'title: (\r\n?|\n)\[(\r\n?|\n)Note(\r\n?|\n)\](\r\n?|\n), (\r\n?|\n)background_color: (\r\n?|\n)brand-color-background.primary'
           - 'title: (\r\n?|\n)\[(\r\n?|\n)Warning(\r\n?|\n)\](\r\n?|\n), (\r\n?|\n)background_color: (\r\n?|\n)brand-color-background.warning'
         -