By Simon Gattner

Images

Created: 2026-07-11

Picture by exiguus

Introduction

This post explains how images are handled in the mono/plain theme:

• where image files should live,
• how to render them in posts,
• how resizing and srcset are generated,
• and how templates/macros build gallery and header images.

The key idea: the theme supports both colocated image paths and page-relative paths, depending on where the image is rendered.

Content Structure

For best results, keep the post and its image files together:

content/
  posts/
    my-post/
      index.md
      hero.jpg
      photo-01.jpg
      photo-02.jpg

That layout works with the theme image shortcodes and gallery helpers without hardcoded global paths.

Images In Post Front Matter

The theme uses these optional front matter fields:

[extra]
hero_img = "hero.jpg"
hero_alt = "Sunset skyline over a river"
hero_copy = "Hackesche Hoefe in Berlin-Mitte"
preview_img = "hero.jpg"
images = ["photo-01.jpg", "photo-02.jpg"]

• extra.hero_img: shown in the post header (templates/components/post_header.html) and it is the fallback for the Open Graph preview image.
• extra.hero_alt: optional alternative text for extra.hero_img.
• extra.hero_copy: optional caption text shown below the hero image.
• extra.preview_img: used first for Open Graph preview generation.
• If extra.preview_img is missing, Open Graph falls back to extra.hero_img.
• extra.images: used by gallery-related templates to render thumbnails. It is also used by the latest images component, so the same image list can drive both post content and gallery views.

Images In Markdown Posts

There are two common ways:

1. Standard Markdown Image

![Alternative text](photo-01.jpg)

Use this when you want plain Markdown behavior. No lazy-loading or responsive srcset is generated. The image path is resolved relative to the page's location, so it works with colocated content or global paths.

2. Theme Image Shortcode (Responsive)

\{\{ image(src="photo-01.jpg", alt="A calm city skyline at dusk") \}\}

When used without explicit width/height, this calls the responsive image macro and generates srcset variants based on theme config.

If you want a fixed output size:

\{\{ image(src="photo-01.jpg", alt="A calm city skyline at dusk", width=800, height=450) \}\}

With width and height set, the shortcode uses a fixed resize path.

Config Extra

Image behavior is controlled in config.toml:

[extra]
image_resizing_disabled = false
image_format = "webp"
image_quality = 80
images_default_size = 256
images_sizes = [256, 384, 512, 576, 640, 768, 1024, 1152]
thumbnail_quality = 70
thumbnail_default_size = 128
thumbnail_sizes = [128, 256]

• image_resizing_disabled = true disables responsive transformation and uses original file paths.
• image_format, image_quality control generated responsive images.
• thumbnail_quality, thumbnail_sizes, thumbnail_default_size control generated thumbnail images.

Post/Page Extra

This is the image-related extra configuration you can use per page/post front matter:

[extra]
hero_img = "hero.jpg"
hero_alt = "Sunset skyline over a river"
hero_copy = "Hackesche Hoefe in Berlin-Mitte"
preview_img = "hero.jpg"
images = ["photo-01.jpg", "photo-02.jpg"]

• hero_img: post header hero image (templates/components/post_header.html).
• hero_alt: post header image alt text. If missing, it falls back to page description and then page title.
• hero_copy: post header figcaption text. If missing, it falls back to page description and then page title.
• preview_img: Open Graph image (templates/macros/opengraph.html).
• images: image list for gallery/latest image components.

Resolution behavior:

• Post header currently uses images::responsive_image(path=page.path, src=page.extra.hero_img, ...).
• Open Graph currently resizes relative image paths using page.path ~ <image-name>.
• The image shortcode uses page.colocated_path and is best used with colocated post bundles.

How Templates Handle Images

The implementation lives in templates/macros/images.html and is reused across pages.

Core Macros

• image(...): plain/fixed image output.
• responsive_image(...): generates srcset using resize_image(..., op="fit_width").
• responsive_thumbnail(...): generates thumbnail variants using resize_image(..., op="fit"|"fill").

Post Header

templates/components/post_header.html renders extra.hero_img as a responsive image inside a figure.

Gallery And Latest Images

templates/pages/gallery.html, templates/components/latest_images.html, and templates/components/post_latest_images.html iterate over post.extra.images and render each with responsive_thumbnail(...).

Template Usage Examples

In templates, import and call the image macros like this:

{% import "macros/images.html" as images %}

{{ images::responsive_image(
  path=page.colocated_path,
  src="photo-01.jpg",
  alt="A calm city skyline at dusk",
  default_size=384,
  sizes=[384, 576, 1200]
) }}

Thumbnail usage:

{{ images::responsive_thumbnail(
  path=post.colocated_path,
  src="photo-01.jpg",
  alt=post.title,
  default_size=128,
  sizes=[128, 256]
) }}

Practical Workflow

1. Put post text and image files in the same colocated post directory.
2. Use extra.hero_img for a hero image.
3. Use extra.images for gallery/latest image blocks.
4. Use \{\{ image(...) \}\} shortcode in Markdown when you want responsive behavior in body content (best with colocated bundles).
5. Tune images_sizes and thumbnail_sizes in config for your performance and quality targets.

Summary

Images in mono/plain are driven by reusable image macros and a mix of path strategies (page.colocated_path and page.path) depending on template context. Responsive behavior remains centralized in one macro file.