@thi.ng/imago/README.md

JSON & API-based declarative and extensible image processing trees/pipelines

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# ![@thi.ng/imago](https://raw.githubusercontent.com/thi-ng/umbrella/develop/assets/banners/thing-imago.svg?e5ca4d48)

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> [!NOTE]
> This is one of 210 standalone projects, maintained as part
> of the [@thi.ng/umbrella](https://github.com/thi-ng/umbrella/) monorepo
> and anti-framework.
>
> 🚀 Please help me to work full-time on these projects by [sponsoring me on
> GitHub](https://github.com/sponsors/postspectacular). Thank you! ❤️

- [About](#about)
  - [Basic example](#basic-example)
- [Supported operations](#supported-operations)
  - [blur](#blur)
  - [composite](#composite)
    - [Common options](#common-options)
    - [Bitmap image layers](#bitmap-image-layers)
    - [Color layers](#color-layers)
    - [Raw bitmap layers](#raw-bitmap-layers)
    - [SVG layers](#svg-layers)
    - [Text layers](#text-layers)
  - [crop](#crop)
  - [dither](#dither)
  - [exif](#exif)
  - [extend](#extend)
  - [gamma](#gamma)
  - [grayscale](#grayscale)
  - [hsbl](#hsbl)
  - [icc](#icc)
  - [nest](#nest)
  - [output](#output)
    - [Templated output paths](#templated-output-paths)
  - [resize](#resize)
  - [rotate](#rotate)
- [Status](#status)
- [Positions & sizes](#positions--sizes)
  - [Gravity](#gravity)
- [Metadata handling](#metadata-handling)
- [Installation](#installation)
- [Dependencies](#dependencies)
- [API](#api)
  - [Multistage processing pipeline](#multistage-processing-pipeline)
- [Authors](#authors)
- [License](#license)

## About

JSON & API-based declarative and extensible image processing trees/pipelines.

Spiritual successor of an eponymous, yet never fully published
CLojure/Java-based image processor from 2014...

In this new TypeScript version all image I/O and processing is delegated to
[sharp](https://sharp.pixelplumbing.com) and
[@thi.ng/pixel](https://github.com/thi-ng/umbrella/blob/develop/packages/pixel).

### Basic example

Transformation trees/pipelines are simple JSON objects (but can be
programmatically created):

The following pipeline performs these steps (in sequence):

- auto-rotate image (using EXIF orientation info, if available)
- add 5% white border (size relative to shortest side)
- proportionally resize image to 1920px (longest side by default)
- overlay bitmap logo layer, positioned at 45% left / 5% bottom
- add custom EXIF metadata
- output this current stage as high quality AVIF (and record expanded output
  path)
- crop center square region
- output as JPEG thumbnail (and record in outputs)
- compute
  [blurhash](https://github.com/thi-ng/umbrella/blob/develop/packages/blurhash)
  (and record in outputs)

```json tangle:export/readme-example1.json
[
    { "op": "rotate" },
    { "op": "extend", "border": 5, "unit": "%", "ref": "min", "bg": "#fff" },
    { "op": "resize", "size": 1920 },
    {
        "op": "composite",
        "layers": [
            {
                "type": "img",
                "path": "logo-128.png",
                "pos": { "l": 45, "b": 5 },
                "unit": "%",
                "blend": "screen"
            }
        ]
    },
    {
        "op": "exif",
        "tags": {
            "IFD0": {
                "Copyright": "Karsten Schmidt",
                "Software": "@thi.ng/imago"
            }
        }
    },
    {
        "op": "output",
        "id": "hires",
        "path": "{name}-{sha256}-{w}x{h}.avif",
        "avif": { "quality": 80 }
    },
    { "op": "crop", "size": [240, 240], "gravity": "c" },
    { "op": "output", "id": "thumb", "path": "{name}-thumb.jpg" },
    { "op": "output", "id": "hash", "blurhash": 4 }
]
```

Then to process an image using above JSON spec (there're also API wrappers to
create these operator specs programmatically):

```ts tangle:export/readme1.ts
import { processImage } from "@thi.ng/imago";
import { readJSON } from "@thi.ng/file-io";

await processImage(
    "test.jpg",
    readJSON("readme-example1.json"),
    { outDir: "." }
);
```

## Supported operations

TODO write docs

### blur

Gaussian blur

- radius

### composite

Compositing multiple layers. The following layer types are available, and custom
layer types can be registered via the polymorphic
[`defLayer()`](https://docs.thi.ng/umbrella/imago/functions/defLayer.html)
function.

#### Common options

- blend mode
- position & origin
- gravity
- tiled repetition

#### Bitmap image layers

- resizable

#### Color layers

- size
- fill color (w/ alpha)

#### Raw bitmap layers

- from typed array or buffer

#### SVG layers

- from file or inline doc

#### Text layers

- optional background color (alpha supported)
- text color
- horizontal/vertical text align
- font family & size
- constrained to text box

### crop

Cropping a part of the image

- from edges, defined region or size & aspect ratio only
- supports px or percent units
- proportional to a given reference side/size

### dither

Supported dither modes from
[thi.ng/pixel-dither](https://github.com/thi-ng/umbrella/blob/develop/packages/pixel-dither):

- "atkinson"
- "burkes"
- "column"
- "diffusion"
- "floyd"
- "jarvis"
- "row"
- "sierra"
- "stucki"

### exif

Set custom EXIF metadata (can be given multiple times, will be merged)

### extend

Add pixels on all sides of the image

- supports px or percent units
- proportional to a given reference side/size
- can be individually configured per side

### gamma

Perform gamma correction (forward or reverse)

### grayscale

Grayscale conversion

### hsbl

Hue, saturation, brightness and lightness adjustments

### icc

Assign ICC profile (from preset: `p3`, `srgb`, `cmyk` or from file). Can only be
given directly prior to [output](#output), overrides input ICC (if any) and only
used if output format actually supports it.

### nest

Performing nested branches/pipelines of operations with no effect on image state
of current/parent pipeline...

### output

File output in any of these formats:

- avif
- gif
- jpeg
- jp2 (JPEG 2000)
- jxl (JPEG XL)
- png
- raw (headless raw data)
- tiff
- webp

Alternatively, a
[blurhash](https://github.com/thi-ng/umbrella/blob/develop/packages/blurhash) of
the image can be computed and stored in the outputs. In this case, no file will
be written.

For all other formats, if no output path is provided in the spec, no file will
be written, but the encoded image buffer itself will be recorded in the outputs.
Use the `raw` output option to obtain the raw pixel data (number of channels
used will depend on previous operations).

```js
import { processImage, output } from "@thi.ng/imago";

const result = await processImage(
    "example.png",
    [output({id: "main", raw: { alpha: false } })]
);

// raw pixel data buffer
result.outputs.main
// <Buffer ...>
```

#### Templated output paths

Output paths can contain `{id}`-templated parts which will be replaced/expanded.
The following built-in IDs are supported and custom IDs will be looked up via
the
[pathParts](https://docs.thi.ng/umbrella/imago/interfaces/ImgProcOpts.html#pathParts)
options provided to
[processImage()](https://docs.thi.ng/umbrella/imago/functions/processImage.html).
Any others will remain as is. Custom IDs take precedence over built-in ones.

- `name`: original base filename (w/o ext)
- `sha1`/`sha224`/`sha256`/`sha384`/`sha512`: truncated hash of output (8 chars)
- `w`: current image width
- `h`: current image height
- `aspect`: "p" (portrait), "l" (landscape) or "sq" (square)
- `date`: yyyyMMdd date format, e.g. 20240223
- `time`: HHmmss time format, e.g. 234459
- `year`: 4-digit year
- `month`: 2-digit month
- `week`: 2-digit week
- `day`: 2-digit day in month
- `hour`: 2-digit hour (24h system)
- `minute`: 2-digit minute
- `second`: 2-digit second

Output paths can contain sub-directories which will be automatically created
(relative to the [configured output
dir](https://docs.thi.ng/umbrella/imago/interfaces/ImgProcOpts.html#outDir)).
For example, the path template `{year}/{month}/{day}/{name}-{sha1}.jpg` might
get replaced to: `2024/02/22/test-123cafe4.jpg`...

### resize

Resizing image

- gravity or position
- fit modes
- supports px or percent units
- proportional to a given reference side/size

### rotate

Auto-rotate, rotate by angle and/or flip image along x/y

## Status

**ALPHA** - bleeding edge / work-in-progress

[Search or submit any issues for this package](https://github.com/thi-ng/umbrella/issues?q=%5Bimago%5D+in%3Atitle)

## Positions & sizes

Border sizes, general dimensions, and positions can be specified in pixels
(default) or as percentages (using `unit: "%"`). For the latter case, an
additional reference side (`ref` option) can be provided. The default ref is
`min`, referring to whatever is the smaller side of an image.

The `ref` option/reference side can take the following values (default: `both`):

- `both`: image width for horizontal uses, image height for vertical uses
- `min`: smaller side of an image (aka `min(width,height)`)
- `max`: larger side of an image (aka `min(width,height)`)
- `w`: image width
- `h`: image height

### Gravity

In some operations positioning or alignment can be abstractly stated via one of
the following gravity values:

![diagram of the 9 possible gravity directions](https://raw.githubusercontent.com/thi-ng/umbrella/develop/assets/imago/gravity.png)

## Metadata handling

By default all input metadata will be lost in the outputs. The `keepEXIF` and
`keepICC` options can be used to retain EXIF and/or ICC profile information
(only if also supported in the output format).

**Important:** Retaining EXIF and merging it with [custom additions](#exif) is
still WIP...

## Installation

```bash
yarn add @thi.ng/imago
```

ESM import:

```ts
import * as imago from "@thi.ng/imago";
```

For Node.js REPL:

```js
const imago = await import("@thi.ng/imago");
```

Package sizes (brotli'd, pre-treeshake): ESM: 5.20 KB

## Dependencies

- [@thi.ng/api](https://github.com/thi-ng/umbrella/tree/develop/packages/api)
- [@thi.ng/blurhash](https://github.com/thi-ng/umbrella/tree/develop/packages/blurhash)
- [@thi.ng/checks](https://github.com/thi-ng/umbrella/tree/develop/packages/checks)
- [@thi.ng/date](https://github.com/thi-ng/umbrella/tree/develop/packages/date)
- [@thi.ng/defmulti](https://github.com/thi-ng/umbrella/tree/develop/packages/defmulti)
- [@thi.ng/errors](https://github.com/thi-ng/umbrella/tree/develop/packages/errors)
- [@thi.ng/file-io](https://github.com/thi-ng/umbrella/tree/develop/packages/file-io)
- [@thi.ng/logger](https://github.com/thi-ng/umbrella/tree/develop/packages/logger)
- [@thi.ng/object-utils](https://github.com/thi-ng/umbrella/tree/develop/packages/object-utils)
- [@thi.ng/pixel](https://github.com/thi-ng/umbrella/tree/develop/packages/pixel)
- [@thi.ng/pixel-dither](https://github.com/thi-ng/umbrella/tree/develop/packages/pixel-dither)
- [@thi.ng/prefixes](https://github.com/thi-ng/umbrella/tree/develop/packages/prefixes)
- [sharp](https://sharp.pixelplumbing.com)

Note: @thi.ng/api is in _most_ cases a type-only import (not used at runtime)

## API

[Generated API docs](https://docs.thi.ng/umbrella/imago/)

### Multistage processing pipeline

```ts tangle:export/readme-api.ts
import {
    colorLayer,
    composite,
    crop,
    extend,
    imageLayer,
    nest,
    output,
    processImage,
    rawLayer,
    resize,
    rotate,
} from "@thi.ng/imago";
import { ConsoleLogger } from "@thi.ng/logger";

const res = await processImage(
    "test.jpg",
    // operator pipeline (i.e. a nested array of operator spec objects)
    // the functions used here are merely syntax sugar for generating
    // the spec objects to provide an anchor point for docs
    // (ongoing effort, but since still a new project, mostly still forthcoming...)
    [
        // auto-rotate (EXIF orientation)
        rotate({}),
        // composite w/ semi-transparent color layer (screen)
        composite({
            layers: [
                colorLayer({
                    // magenta with 50% opacity
                    bg: "#f0f8",
                    blend: "screen",
                    // layer size is 50x100% of image
                    size: [50, 100],
                    // aligned left (west)
                    gravity: "w",
                    // size given in percent
                    unit: "%",
                }),
                // diagonal hairline pattern overlay (with tiling) from raw
                // pixel data in ABGR format, i.e. 0xAABBGGRR
                rawLayer({
                    // prettier-ignore
                    buffer: new Uint32Array([
                        0x00000000, 0x00000000, 0x00000000, 0x80ffffff,
                        0x00000000, 0x00000000, 0x80ffffff, 0x00000000,
                        0x00000000, 0x80ffffff, 0x00000000, 0x00000000,
                        0x80ffffff, 0x00000000, 0x00000000, 0x00000000,
                    ]),
                    channels: 4,
                    size: [4, 4],
                    tile: true,
                }),
            ],
        }),
        // nested operations each operate on a clone of the current (already
        // semi-transformed) image, they have no impact on the processing pipeline
        // of their parent(s)
        // multiple child pipelines can be spawned, here only a single one
        nest({
            procs: [
                // this pipeline only creates blurhash (stored in `outputs` of result)
                [resize({ size: 100 }), output({ id: "hash", blurhash: true })],
            ],
        }),
        // crop to 3:2 aspect ratio (always based on longest side)
        crop({ size: 100, aspect: 3 / 2, unit: "%" }),
        // back in the main pipleline, add 5% white border (based on smallest side)
        extend({ border: 5, unit: "%", bg: "white", ref: "min" }),
        // resize image to 1920 (largest side)
        resize({ size: 1920 }),
        // add logo watermark centered horizontally and near the bottom
        composite({
            layers: [
                imageLayer({
                    path: "logo-128.png",
                    unit: "%",
                    origin: "s",
                    pos: { l: 50, b: 5 },
                    ref: "both",
                    blend: "screen",
                }),
            ],
        }),
        output({ id: "main", path: "{date}-1920-frame.jpg" }),
    ],
    {
        logger: new ConsoleLogger("img"),
    }
);

console.log(res.outputs);
// {
//   hash: "UVKmR.^SIVR$_NRiM{jupLRjjEWC%goxofoM",
//   main: "...../20240301-144948-1920-frame.jpg",
// }
```

## Authors

- [Karsten Schmidt](https://thi.ng)

If this project contributes to an academic publication, please cite it as:

```bibtex
@misc{thing-imago,
  title = "@thi.ng/imago",
  author = "Karsten Schmidt",
  note = "https://thi.ng/imago",
  year = 2024
}
```

## License

&copy; 2024 - 2025 Karsten Schmidt // Apache License 2.0