imgroll

A smart image optimization library / local executable / AWS Lambda function. Primarily designed for sweetroll2.

• Extracts some useful metadata using exiv2
• Applies rotation specified in metadata
• Generates tiny WebP data URI placeholders/previews
• Extracts a color palette using color-thief
• Produces up to three sizes for each output format
• Processes output formats in parallel
• Outputs a JSON object describing the resulting images and the extracted metadata

The output formats depend on the input format.

• For PNGs:
  • quantizes colors with exoquant
  • outputs PNGs compressed with the Rust port of Zopfli
• For JPEGs:
  • outputs progressive JPEGs compressed with MozJPEG
  • outputs WebPs compressed with libwebp

The Lambda function responds to S3 uploads that contain imgroll-cb in metadata. That value is used as a "processing done" callback, sending a JSON body with the resulting object. The BUCKET_PUBLIC_HOST environment variable can be used to specify a host for use in output URLs instead of the default S3 host (for use with CloudFront/CNAMEs).

Schema/Examples

{
  "aperture": 10,
  "focal_length": 27,
  "geo": null,
  "height": 2916,
  "iso": 100,
  "palette": [
    { "b": 106, "g": 89, "r": 58 },
    { "b": 198, "g": 201, "r": 201 },
    { "b": 140, "g": 143, "r": 146 },
    { "b": 25, "g": 23, "r": 2 },
    { "b": 41, "g": 47, "r": 52 },
    { "b": 181, "g": 149, "r": 101 },
    { "b": 191, "g": 183, "r": 159 },
    { "b": 153, "g": 141, "r": 113 },
    { "b": 128, "g": 140, "r": 172 }
  ],
  "shutter_speed": [ 1, 320 ],
  "source": [
    {
      "original": false,
      "srcset": [
        {
          "src": "https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.3000.jpg",
          "width": 3000
        },
        {
          "src": "https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.2000.jpg",
          "width": 2000
        },
        {
          "src": "https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.1000.jpg",
          "width": 1000
        }
      ],
      "type": "image/jpeg"
    },
    {
      "original": false,
      "srcset": [
        {
          "src": "https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.3000.webp",
          "width": 3000
        },
        {
          "src": "https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.2000.webp",
          "width": 2000
        },
        {
          "src": "https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.1000.webp",
          "width": 1000
        }
      ],
      "type": "image/webp"
    },
    {
      "original": true,
      "srcset": [
        {
          "src": "https://dl.unrelenting.technology/IMG-7081.jpg",
          "width": 5184
        }
      ],
      "type": "image/jpeg"
    }
  ],
  "tiny_preview": "data:image/webp;base64,UklGRnAAAABXRUJQVlA4IGQAAAAwBACdASowABoAP93k6Gy/urEptVv8A/A7iWpn5FtTI0FdNumdDYJBregA/QjOCu+Vax2w/NNsn1WlEoWM/p71MMMgguqBQEtfbHi8eOBhwhKVvNAzA0Rvwyv7z3kaGgxQoYAA",
  "width": 5184
}

And here's the kind of HTML sweetroll2 can generate from that:

<figure class="entry-photo">
  <responsive-container style="padding-bottom: 56.25%; background: rgb(58, 89, 106) url(&quot;data:image/webp;base64,UklGRnAAAABXRUJQVlA4IGQAAAAwBACdASowABoAP93k6Gy/urEptVv8A/A7iWpn5FtTI0FdNumdDYJBregA/QjOCu+Vax2w/NNsn1WlEoWM/p71MMMgguqBQEtfbHi8eOBhwhKVvNAzA0Rvwyv7z3kaGgxQoYAA&quot;) repeat scroll 0% 0%;">
    <picture>
      <source srcset="https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.3000.webp 3000w,
                      https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.2000.webp 2000w,
                      https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.1000.webp 1000w" type="image/webp">
      <img alt="" class="u-photo"
           src="https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.3000.jpg"
           srcset="https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.3000.jpg 3000w,
                   https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.2000.jpg 2000w,
                   https://dl.unrelenting.technology/4a0c45a0ed40_img-7081.1000.jpg 1000w">
    </picture>
  </responsive-container>
  <figcaption class="entry-photo-meta">
    <svg aria-hidden="false" class="icon" role="image" title="Photo parameters"><use xlink:href="/__as__/icons.svg?vsn=tMCAZl1CLU8yDTq2PdhyDgna#eye"><title>Photo parameters</title></use></svg>
    <span class="camera-focal-length">27 mm</span>
    <span class="camera-iso">ISO 100</span>
    <span class="camera-shutter">1/320</span>
    <span class="camera-aperture">ƒ/10</span>
    <svg aria-hidden="true" class="icon" role="image"><use xlink:href="/__as__/icons.svg?vsn=tMCAZl1CLU8yDTq2PdhyDgna#desktop-download"></use></svg>
    <a class="camera-original" href="https://dl.unrelenting.technology/IMG-7081.jpg">Download original</a>
  </figcaption>
</figure>

License

This is free and unencumbered software released into the public domain.
For more information, please refer to the UNLICENSE file or unlicense.org.

(Note: different licenses apply to dependencies.)