Add dark background (#1024)

Co-authored-by: Emruz Hossain <hossainemruz@gmail.com>

layouts/partials/sections/home.html

@@ -20,6 +20,10 @@
   {{ $backgroundImage = site.Params.background }}
 {{ end }}
 
+{{ $darkBackgroundImage:= $backgroundImage }}
+{{ if site.Params.darkBackground }}
+  {{ $darkBackgroundImage = site.Params.darkBackground }}
+{{ end }}
 
 {{ $authorImage:= "/images/default-avatar.png" }}
 {{ if $author.image }}
@@ -73,6 +77,41 @@
   {{ $large := $src}}
 {{ end }}
 
+{{/* get file that matches the filename as specified as src="" in shortcode */}}
+{{ $darkSrc := resources.Get $darkBackgroundImage }}
+
+{{/* resize the src image to the given sizes */}}
+
+{{ $darkTiny := $darkSrc.Resize $tinyw }}
+{{ $darkSmall := $darkSrc.Resize $smallw }}
+{{ $darkMedium := $darkSrc.Resize $mediumw }}
+{{ $darkLarge := $darkSrc.Resize $largew }}
+
+{{/* only use images smaller than or equal to the src (original) image size, as Hugo will upscale small images */}}
+{{/* set the sizes attribute to (min-width: 35em) 1200px, 100vw unless overridden in shortcode */}}
+
+{{ if lt $darkSrc.Width "500" }}
+  {{ $darkTiny := $src}}
+  {{ $darkSmall := $src}}
+  {{ $darkMedium := $src}}
+  {{ $darkLarge := $src}}
+{{ end }}
+
+{{ if lt $src.Width "800" }}
+  {{ $darkSmall := $src}}
+  {{ $darkMedium := $src}}
+  {{ $darkLarge := $src}}
+{{ end }}
+
+{{ if lt $src.Width "1200" }}
+  {{ $darkMedium := $src}}
+  {{ $darkLarge := $src}}
+{{ end }}
+
+{{ if lt $src.Width "1500" }}
+  {{ $darkLarge := $src}}
+{{ end }}
+
 <div class="container-fluid home" id="home">
   <style>
     /* 0 to 299 */
@@ -100,6 +139,34 @@
           background-image: url('{{ $src.RelPermalink }}');
         }
     }
+
+    html[data-theme='dark'] {
+      /* 0 to 299 */
+      #homePageBackgroundImageDivStyled {
+        background-image: url('{{ $darkTiny.RelPermalink }}');
+      }
+      /* 300 to X */
+      @media (min-width: 500px) and (max-width: 800px) { /* or 301 if you want really the same as previously.  */
+        #homePageBackgroundImageDivStyled {   
+          background-image: url('{{ $darkSmall.RelPermalink }}');
+        }
+      }
+      @media (min-width: 801px) and (max-width: 1200px) { /* or 301 if you want really the same as previously.  */
+        #homePageBackgroundImageDivStyled {   
+          background-image: url('{{ $darkMedium.RelPermalink }}');
+        }
+      }
+      @media (min-width: 1201px) and (max-width: 1500px) { /* or 301 if you want really the same as previously.  */
+        #homePageBackgroundImageDivStyled {   
+          background-image: url('{{ $darkLarge.RelPermalink }}');
+        }
+      }
+      @media (min-width: 1501px) { /* or 301 if you want really the same as previously.  */
+        #homePageBackgroundImageDivStyled {   
+          background-image: url('{{ $darkSrc.RelPermalink }}');
+        }
+      }
+    }
     </style>
     <span class="on-the-fly-behavior"></span>
   <div