Fix orientation of thumbnails

(cherry picked from commit f6a698a64b)

layouts/_markup/render-image.html

@@ -9,8 +9,11 @@ An image on its own line becomes a figure; images sharing a paragraph get an inl
 {{- with or (.PageInner.Resources.Get (strings.TrimPrefix "./" .Destination)) (resources.Get .Destination) -}}
   {{- $src = .RelPermalink -}}
   {{- if and (eq .ResourceType "image") (ne .MediaType.SubType "svg") -}}
-    {{- $width = .Width -}}
-    {{- $height = .Height -}}
+    {{- /* Width and height as the browser shows the image, i.e. turned as its EXIF orientation
+    says (only JPEG and TIFF carry one). */ -}}
+    {{- $shown := cond (in (slice "jpeg" "tiff") .MediaType.SubType) (.Filter images.AutoOrient) . -}}
+    {{- $width = $shown.Width -}}
+    {{- $height = $shown.Height -}}
   {{- end -}}
 {{- end -}}
 {{- /* A title that only repeats the alt text is not a credit. */ -}}