srcsetter#

Responsive image generation for HTML srcset attributes.

Overview#

Srcsetter processes a directory of images and outputs responsive variants suitable for embedding as <img srcset> tags in websites. It uses ImageMagick for image processing and outputs WebP format.

Packages#

• srcsetter - Core library for image entry management
• srcsetter-cmd - CLI tool for batch processing

Installation#

opam install srcsetter     # Library only
opam install srcsetter-cmd # CLI tool (includes library)

Usage#

Library#

(* Load entries from JSON *)
match Srcsetter.list_of_json json_string with
| Ok entries ->
    List.iter (fun entry ->
      let name = Srcsetter.name entry in
      let (w, h) = Srcsetter.dims entry in
      Printf.printf "%s: %dx%d\n" name w h;
      (* Access variants *)
      Srcsetter.MS.iter (fun variant_name (vw, vh) ->
        Printf.printf "  %s: %dx%d\n" variant_name vw vh
      ) (Srcsetter.variants entry)
    ) entries
| Error msg -> Printf.printf "Error: %s\n" msg

CLI#

srcsetter process input_dir/ output_dir/

Image Entry Structure#

Each entry tracks:

• name - Output filename (e.g., photo.webp)
• slug - URL-safe identifier
• origin - Original source file path
• dims - Base image dimensions (width, height)
• variants - Map of variant filenames to dimensions

JSON Format#

[
  {
    "name": "photo.webp",
    "slug": "photo",
    "origin": "photos/DSC_1234.jpg",
    "dims": [1920, 1080],
    "variants": {
      "photo-640.webp": [640, 360],
      "photo-1280.webp": [1280, 720]
    }
  }
]

Requirements#

• ImageMagick CLI tools

License#

ISC