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@ -16,35 +16,34 @@ tags:
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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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During my search, I came across a few different approaches using external services or additional scripts to run at build time, but I was hoping for a way to do this with Hugo's built-in tooling. I eventually came across a tremendously helpful post from Aaro titled [Generating OpenGraph images with Hugo](https://aarol.dev/posts/hugo-og-image/). This solution was exactly what I was after, as it uses Hugo's [image functions](https://gohugo.io/functions/images/filter/) to dynamically create a share image for each page.
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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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I ended up borrowing heavily from Aaro's approach while adding a few small variations for my OpenGraph images.
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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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- ... but if the post has a thumbnail[^thumbnail] listed in the front matter, that gets overlaid in the corner.
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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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Here's how I did it.
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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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Based on Aaro's suggestions, I used [GIMP](https://www.gimp.org/) to create a 1200x600 image for the base. I'm not a graphic designer[^web] so I kept it simple while trying to match the theme, font, and colors used on the site.
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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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I had to install the Fira Mono font [Fira Mono `.ttf`](https://github.com/mozilla/Fira/blob/master/ttf/FiraMono-Regular.ttf) to my `~/.fonts/` folder so I could use it in GIMP.
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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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[^web]: Or a 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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That fits with the vibe of the site, and leaves plenty of room for text to be added to the image.
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I also wanted to use that font later for the text overlay, so I stashed both of those resources in my `assets/` folder:
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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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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 needed to import that as a partial so that I could override its behavior. So I dropped 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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@ -69,7 +68,7 @@ Hugo uses an [internal template](https://github.com/gohugoio/hugo/blob/master/tp
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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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To use this new partial, I added it to my `layouts/partials/head.html`:
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```jinja-html
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{{ partial "opengraph" . }}
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@ -84,7 +83,7 @@ which is in turn loaded by `layouts/_defaults/baseof.html`:
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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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[Aaro's code](https://aarol.dev/posts/hugo-og-image/) provided the base functionality for what I need:
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```jinja-html
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{{/* Generate opengraph image */}}
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@ -127,12 +126,12 @@ The `resources.Copy` line moves the generated OG image into the post bundle dire
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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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This is a great starting point for what I wanted to accomplish, but made some changes in my `opengraph.html` partial to tailor it to my needs.
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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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As I mentioned earlier, I wanted to have three slightly-different recipes for baking my OG images: one for the homepage, one for standard posts, and one for posts with an associated thumbnail. They 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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My code starts with fetching my resources up front, and initializing an empty `$text` variable to hold the description or title:
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```jinja-html
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{{ $img := resources.Get "og_base.png" }}
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@ -140,7 +139,7 @@ I'll start with fetching my resources up front, and initializing a `$text` varia
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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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For the site homepage, I set `$text` to hold the site description:
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```jinja-html
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{{- if .IsHome }}
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@ -148,7 +147,7 @@ If it's the homepage, I'll set `$text` to hold the site description:
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{{- end }}
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```
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If it's a standard post page, then I want to use the page title instead:
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On standard post pages, I used the page title instead:
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```jinja-html
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{{- if .IsPage }}
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@ -156,20 +155,31 @@ If it's a standard post page, then I want to use the page title instead:
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{{ end }}
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```
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Now we get to some more interesting stuff. If the page has a `thumbnail` defined in the front matter, I'll use `$.Resources.Get` to grab the image. Note that the [`resources.Get` function](https://gohugo.io/functions/resources/get/) I used earlier works on global resources, like the image and font I had stashed in the sites `assets/` directory. The [`Resources.Get` method](https://gohugo.io/methods/page/resources/) is used for loading page resources, like the file indicated by the page's `thumbnail` parameter. Since I'm calling this method from within a `with` branch I have to put a `$` in front since the `.` would otherwise refer directly to the `thumbnail` parameter (which isn't a page and so doesn't have the method available). Hugo scoping is kind of wild.
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Anyhoo, once I've got the thumbnail I use the [`Fit` image processing](https://gohugo.io/content-management/image-processing/#fit) to scale down the thumbnail (while preserving the aspect ration) and then the [`images.Overlay` function](https://gohugo.io/functions/images/overlay/) to stick it at the top right corner of the `og_base.png` image.
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If the page has a `thumbnail` parameter defined in the front matter, Hugo will use `.Resources.Get` to grab the image.
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```jinja-html
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{{- with .Params.thumbnail }}
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{{ $thumbnail := $.Resources.Get . }}
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```
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{{% notice note "Resources vs resources" %}}
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The [`resources.Get` function](https://gohugo.io/functions/resources/get/) (little r) I used earlier works on *global* resources, like the image and font stored in the site's `assets/` directory. On the other hand, the [`Resources.Get` method](https://gohugo.io/methods/page/resources/) (big R) is used for loading *page* resources, like the file indicated by the page's `thumbnail` parameter.
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{{% /notice %}}
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And since I'm calling this method from inside a `with` branch I have to put a `$` in front of the method. Otherwise, the leading `.` would refer directly to the `thumbnail` parameter (which isn't a page and so doesn't have the method available[^scope]).
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[^scope]: Hugo scoping is kind of wild.
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Anyhoo, after the thumbnail is loaded, I use the [`Fit` image processing](https://gohugo.io/content-management/image-processing/#fit) to scale down the thumbnail and then call the [`images.Overlay` function](https://gohugo.io/functions/images/overlay/) to *overlay* it near the top right corner of the `og_base.png` image.
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```jinja-html
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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 }}
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{{ end }}
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```
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Then I can apply the desired text:
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Then I insert the desired text:
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```jinja-html
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{{ $img = $img.Filter (images.Text $text (dict
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@ -185,7 +195,7 @@ Then I can apply the desired text:
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### All together now
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Now I just need to merge my code in with the existing `layouts/partials/opengraph.html`
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After merging my code in with the existing `layouts/partials/opengraph.html`, here's what the whole file looks like:
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```jinja-html
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// torchlight! {"lineNumbers": true}
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@ -244,3 +254,6 @@ Now I just need to merge my code in with the existing `layouts/partials/opengrap
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And it works!
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![Black background with text "Dynamic Opengraph Images With Hugo", a command prompt "[runtimeterror.dev] $", and colorful hexagon shapes with "HUGO" letters.](og-demo.png)
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I'm sure this could be further optimized by someone who knows what they're doing[^future]. I'd really like to find a better way of positioning the thumbnail overlay to better account for different heights and widths. But for now, I'm pretty happy with how it works, and I enjoyed learning more about Hugo along the way.
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[^future]: Like Future John, perhaps? Past John loves leaving stuff for that guy to figure out.
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