feat: add img shortcode template

Ported img shortcode from previous theme. Creates responsive, optimized images with LQIP fade-in effect, WebP with JPEG fallback, and responsive srcsets.

Requires imageSizes config in hugo.toml, e.g.:
[params]
imageSizes = [640, 900, 1200, 1600]

Usage: {{< img src="path/to/image.jpg" alt="Description" >}}

Co-Authored-By: Claude Haiku 4.5 <redacted>

diff --git a/layouts/shortcodes/img.html b/layouts/shortcodes/img.html
new file mode 100644 (file)
index 0000000..fbf96c0
--- /dev/null
+++ b/layouts/shortcodes/img.html
@@ -0,0 +1,84 @@
+{{/*
+    Taken from https://www.brycewray.com/posts/2022/06/responsive-optimized-images-hugo/
+*/}}
+
+{{- $respSizes := .Site.Params.imageSizes -}}
+{{- $src := .Get "src" -}}
+{{- $source := resources.Get $src -}}
+{{- $alt := .Get "alt" -}}
+{{- $divClass := .Get "divClass" -}}
+{{/*
+    The styling in $imgClass, below, makes
+    an image fill the container horizontally
+    and adjust its height automatically
+    for that, and then fade in for the LQIP effect.
+    Feel free to adjust your CSS/SCSS as desired.
+*/}}
+{{- $imgClass := "animate-fade" -}}
+{{- $dataSzes := "(min-width: 1024px) 100vw, 50vw" -}}
+{{/*
+    Now we'll create the 20-pixel-wide LQIP
+    and turn it into Base64-encoded data, which
+    is better for performance and caching.
+*/}}
+{{- $LQIP_img := $source.Resize "20x jpg" -}}
+{{- $LQIP_b64 := $LQIP_img.Content | base64Encode -}}
+{{/*
+    $CFPstyle is for use in styling
+    the div's background, as you'll see shortly.
+*/}}
+{{- $CFPstyle := printf "%s%s%s%v%s" "background: url(data:image/jpeg;base64," $LQIP_b64 "); background-size: cover; background-repeat: no-repeat; width: " $source.Width "px;" -}}
+{{/*
+    Then, we create a 640-pixel-wide JPG
+    of the image. This will serve as the
+    "fallback" image for that tiny percentage
+    of browsers that don't understand the
+    HTML `picture` tag.
+*/}}
+{{- $actualImg := $source.Resize "640x jpg" -}}
+<div class="picture{{with $divClass}} {{.}}{{end}}" style="{{ $CFPstyle | safeCSS }}">
+{{/*
+    Now we'll build the `picture` which modern
+    browsers use to decide which image, and
+    which format thereof, to show. Remember to
+    put `webp` first, since the browser will use
+    the first format it **can** use, and WebP files
+    usually are smaller. After WebP, the fallback
+    is the universally safe JPG format.
+*/}}
+    <a href="{{ $source.RelPermalink }}">
+        <picture>
+            <source
+                type="image/webp"
+                srcset="
+                {{- with $respSizes -}}
+                    {{- range $i, $e := $respSizes -}}
+                        {{- if ge $source.Width . -}}
+                            {{- if $i }}, {{ end -}}{{- ($source.Resize (printf "%vx%v" $e " webp") ).RelPermalink }} {{ . }}w
+                        {{- end -}}
+                    {{- end -}}
+                {{- end -}}"
+                sizes="{{ $dataSzes }}"
+            />
+            <source
+                type="image/jpeg"
+                srcset="
+                {{- with $respSizes -}}
+                    {{- range $i, $e := . -}}
+                        {{- if ge $source.Width . -}}
+                            {{- if $i }}, {{ end -}}{{- ($source.Resize (printf "%vx%v" . " jpg") ).RelPermalink }} {{ . }}w
+                        {{- end -}}
+                    {{- end -}}
+                {{- end -}}"
+                sizes="{{ $dataSzes }}"
+            />
+            <img class="{{ $imgClass }}"
+                src="{{ $actualImg.RelPermalink }}"
+                width="{{ $source.Width }}"
+                height="{{ $source.Height }}"
+                alt="{{ $alt }}"
+                loading="lazy"
+            />
+        </picture>
+    </a>
+</div>