Special thanks to Guillermo Esteves @allencompassingtrip.com, whose Rails photoblogging CMS features a Bluesky integration which was my inspiration to build this project.

Since the demise of Twitter, I’ve been posting to Bluesky. The communities that have formed there are lovely, including lots of fellow photographers, and I wanted to start sharing photos from my Photolog to Bluesky on a daily basis. Here’s what one of those posts looks like!

The Bluesky app works like Twitter – you can post small messages and attach images, videos, or a website embed. It’s different from Twitter in that it is based on the AT Protocol, which makes Bluesky more like an app that runs on top of an open database. So, instead of making a REST request to the Bluesky API, you “insert into the database” and your post shows up in the app.

My goal was to write a text post, attach an image, and run this code daily with a random photo. AT Protocol complicates things a little bit compared to a POST /posts/new REST API in that the AT Protocol is data-oriented rather than task-oriented. This means you have to perform the intermediate steps to construct the parts of a post before assembling them into a completed post.

Since I’m using Astro to post my photos, it was easy enough to update my template to add a photos.json file with content for daily posts.

How To

The Bluesky team has some documentation on posting with images, but these docs use Python and are not terribly complete, so I wanted to share my complete and working example of the Node.js TypeScript code I use to post to Bluesky.

Here are the steps from the above code described in detail:

Upload image data to Bluesky

This results in a blob, a bit of structured data which points to the uploaded image. You can’t upload an image of > 1 MB and you have to strip the image metadata yourself. At this time, these are both responsibilities of the client.

To upload content to Bluesky, you use the ATP Agent with a set of credentials (username & app-specific password). Under the hood, this is performing REST requests for you.

Build the image metadata

Construct an app.bsky.embed.images object by passing the image data blob. You have to provide the aspect ratio of your image in this part, or the image won’t be rendered properly in the official clients.

Build the post content

Assemble the rich text for the post. To add stuff like inline links, hashtags, or @ mentions, you provide the raw string alongside facets, bits of data which indicate a range of string characters should point to a target thing. Bluesky’s SDK provides a helper to turn raw text into rich text.

Finally, build an app.bsky.feed.post by combining the text, facets, image embed, and created at date. You can actually back/forward date stuff as part of how the protocol works. Some people use this to import their posts from other social media sites onto ATProto.

Post it

Use the same ATP Agent we used in the image upload step to upload this post to Bluesky, and you’re done!

Posting Daily

To run this task daily, I created a Netlify app with one scheduled function configured to run at 09:00 Mountain Time. I want this script to try not to repost images that have been posted recently, but I don’t want to maintain a database of recent posts. So I implemented the following:

• Get the date of the most recently added image (the basis date)
• Shuffle the list of images using the basis date as the RNG seed
• Get the distance in days between the basis date and now
• Pick the photo to post from the shuffled images at index [daysSince % imageCount]

With this scheme, the script will go through all images in order, only repeating after each image has been posted once. When I add new images – a relatively infrequent operation – the basis date changes, the images are reshuffled, and the script starts posting sequentially from that point. This is the only time that there’s a risk of posting the same image twice in a row, but I’m OK with the low chance of that happening in exchange me not having to run a database for this project.