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183 lines
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8.8 KiB
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183 lines
No EOL
8.8 KiB
Markdown
---
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title: "Dynamic Opengraph Images With Hugo"
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date: 2024-02-18
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# lastmod: 2024-02-18
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draft: true
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description: "This is a new post about..."
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featured: false
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toc: true
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comments: true
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thumbnail: thumbnail.png
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categories: Backstage
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tags:
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- hugo
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- meta
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- selfhosting
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---
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I've lately seen some folks on [social.lol](https://social.lol) posting about their various strategies for automatically generating [Open Graph images](https://ogp.me/) for their [Eleventy](https://11ty.dev) sites. So this weekend I started exploring ways to do that for my [Hugo](https://gohugo.io) site.
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During my search, I came across a few different approaches using external services or additional scripts to run at build time. I eventually came across a post from Aaro titled [Generating OpenGraph images with Hugo](https://aarol.dev/posts/hugo-og-image/) which seemed like exactly what I was after, as it uses Hugo's built-in [image functions](https://gohugo.io/functions/images/filter/) to dynamically create the image by layering text on top of a base.
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I ended up borrowing heavily from Aaro's approach with a few variants for the OpenGraph image:
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- When sharing the home page, the image includes the site description.
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- When sharing a post, the image includes the post title.
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- ... but if the post has a thumbnail[^thumbnail] listed in the front matter, that gets added to the corner of the `og:image`.
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[^thumbnail]: My current theme doesn't make use of the thumbnails, but a previous theme did so I've got a bunch of posts with thumbnails still assigned. And now I've got a use for them again!
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I'm sure this could be further optimized by someone who knows what they're doing[^future]. In any case, here's what I did to get this working.
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[^future]: Like Future John, perhaps? Past John loves leaving stuff for that guy to figure out.
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### New resources
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Based on Aaro's suggestions, I started by creating a 1200x600 image to use as the base. I used [GIMP](https://www.gimp.org/) for this.
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I'm not a graphic designer[^web] so I kept it simple. I wanted to be sure that the text matched the font used on the site, so I downloaded the [Fira Mono `.ttf`](https://github.com/mozilla/Fira/blob/master/ttf/FiraMono-Regular.ttf) to `~/.fonts/` to make it available within GIMP. And then I emulated the colors and style of the "logo" displayed at the top of the page.
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![Red background with a command prompt displaying "[runtimeterror.dev] $" in white and red font.](og_base.png)
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[^web]: Or web designer, if I'm being honest.
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That fits with the theme of the site, and leaves plenty of room for text to be added to the image.
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I'll want to also use that font for the text overlay, so I stashed both of those resources in my `assets/` folder:
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### OpenGraph partial
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Hugo uses an [internal template](https://github.com/gohugoio/hugo/blob/master/tpl/tplimpl/embedded/templates/opengraph.html) for rendering OpenGraph properties by default. I'll need to import that as a partial so that I can override its behavior. So I drop the following in `layouts/partials/opengraph.html` as a starting point:
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```jinja-html
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// torchlight! {"lineNumbers": true}
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<meta property="og:title" content="{{ .Title }}" />
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<meta property="og:description" content="{{ with .Description }}{{ . }}{{ else }}{{if .IsPage}}{{ .Summary }}{{ else }}{{ with .Site.Params.description }}{{ . }}{{ end }}{{ end }}{{ end }}" />
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<meta property="og:type" content="{{ if .IsPage }}article{{ else }}website{{ end }}" />
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<meta property="og:url" content="{{ .Permalink }}" />
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<meta property="og:locale" content="{{ .Lang }}" />
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{{- if .IsPage }}
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{{- $iso8601 := "2006-01-02T15:04:05-07:00" -}}
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<meta property="article:section" content="{{ .Section }}" />
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{{ with .PublishDate }}<meta property="article:published_time" {{ .Format $iso8601 | printf "content=%q" | safeHTMLAttr }} />{{ end }}
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{{ with .Lastmod }}<meta property="article:modified_time" {{ .Format $iso8601 | printf "content=%q" | safeHTMLAttr }} />{{ end }}
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{{- end -}}
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{{- with .Params.audio }}<meta property="og:audio" content="{{ . }}" />{{ end }}
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{{- with .Params.locale }}<meta property="og:locale" content="{{ . }}" />{{ end }}
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{{- with .Site.Params.title }}<meta property="og:site_name" content="{{ . }}" />{{ end }}
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{{- with .Params.videos }}{{- range . }}
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<meta property="og:video" content="{{ . | absURL }}" />
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{{ end }}{{ end }}
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```
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To use this new partial, I'll add it to my `layouts/partials/head.html`:
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```jinja-html
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{{ partial "opengraph" . }}
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```
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which is in turn loaded by `layouts/_defaults/baseof.html`:
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```jinja-html
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<head>
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{{- partial "head.html" . -}}
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</head>
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```
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### Aaro's OG image generation
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[Aaro's code](https://aarol.dev/posts/hugo-og-image/) provides the base functionality for what I need:
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```jinja-html
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{{/* Generate opengraph image */}}
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{{- if .IsPage -}}
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{{ $base := resources.Get "og_base.png" }}
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{{ $boldFont := resources.Get "/Inter-SemiBold.ttf"}}
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{{ $mediumFont := resources.Get "/Inter-Medium.ttf"}}
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{{ $img := $base.Filter (images.Text .Site.Title (dict
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"color" "#ffffff"
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"size" 52
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"linespacing" 2
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"x" 141
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"y" 117
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"font" $boldFont
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))}}
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{{ $img = $img.Filter (images.Text .Page.Title (dict
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"color" "#ffffff"
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"size" 64
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"linespacing" 2
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"x" 141
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"y" 291
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"font" $mediumFont
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))}}
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{{ $img = resources.Copy (path.Join .Page.RelPermalink "og.png") $img }}
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<meta property="og:image" content="{{$img.Permalink}}">
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<meta property="og:image:width" content="{{$img.Width}}" />
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<meta property="og:image:height" content="{{$img.Height}}" />
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<!-- Twitter metadata (used by other websites as well) -->
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<meta name="twitter:card" content="summary_large_image" />
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<meta name="twitter:title" content="{{ .Title }}" />
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<meta name="twitter:description" content="{{ with .Description }}{{ . }}{{ else }}{{if .IsPage}}{{ .Summary }}{{ else }}{{ with .Site.Params.description }}{{ . }}{{ end }}{{ end }}{{ end -}}"/>
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<meta name="twitter:image" content="{{$img.Permalink}}" />
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{{ end }}
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```
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The [`resources.Get`](https://gohugo.io/functions/resources/get/) bits import the image and font resources to make them available to the [`images.Text`](https://gohugo.io/functions/images/text/) functions, which add the site and page title texts to the image using the designated color, size, placement, and font.
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The `resources.Copy` line moves the generated OG image into the post bundle directory and gives it a clean `og.png` name rather than the very-long randomly-generated name it would have by default.
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And then the `<meta ... />` lines insert the generated image into the page's `<head>` block so it can be rendered when the link is shared on sites which support OpenGraph.
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This is a great starting point for what I want to accomplish, but I'm going to make some changes in my `opengraph.html` partial.
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### My tweaks
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As I mentioned earlier, I want to have basically three recipes for baking my OG images: one for the homepage, one for standard posts, and one for posts with an associated thumbnail. They'll all use the same basic code, though, so I wanted to be sure that my setup didn't repeat itself too much.
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I'll start with fetching my resources up front, and initializing a `$text` variable:
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```jinja-html
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{{ $img := resources.Get "og_base.png" }}
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{{ $font := resources.Get "/FiraMono-Regular.ttf" }}
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{{ $text := "" }}
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```
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If it's the homepage, I'll set `$text` to hold the site description:
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```jinja-html
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{{- if .IsHome }}
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{{ $text = .Site.Params.Description }}
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{{- end }}
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```
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{{- if .IsPage }}
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{{ $text = .Page.Title }}
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{{ end }}
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{{- with .Params.thumbnail }}
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{{ $thumbnail := $.Resources.Get . }}
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{{ with $thumbnail }}
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{{ $img = $img.Filter (images.Overlay (.Process "fit 300x250") 875 38 )}}
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{{ end }}{{ end }}
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{{ $img = $img.Filter (images.Text $text (dict
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"color" "#d8d8d8"
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"size" 64
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"linespacing" 2
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"x" 40
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"y" 300
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"font" $font
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))}}
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{{ $img = resources.Copy (path.Join $.Page.RelPermalink "og.png") $img }}
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<meta property="og:image" content="{{$img.Permalink}}">
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<meta property="og:image:width" content="{{$img.Width}}" />
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<meta property="og:image:height" content="{{$img.Height}}" />
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<meta name="twitter:card" content="summary_large_image" />
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<meta name="twitter:title" content="{{ .Title }}" />
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<meta name="twitter:description" content="{{ with .Description }}{{ . }}{{ else }}{{if .IsPage}}{{ .Summary }}{{ else }}{{ with .Site.Params.description }}{{ . }}{{ end }}{{ end }}{{ end -}}"/>
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<meta name="twitter:image" content="{{$img.Permalink}}" />
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{{- with .Params.audio }}<meta property="og:audio" content="{{ . }}" />{{ end }}
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{{- with .Site.Params.title }}<meta property="og:site_name" content="{{ . }}" />{{ end }}
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{{- with .Params.videos }}{{- range . }}
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<meta property="og:video" content="{{ . | absURL }}" />
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{{ end }}{{ end }}
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``` |