libultrahdr.Function.encodeJPEGMetadata

@monogrid/gainmap-js / libultrahdr / encodeJPEGMetadata

Function: encodeJPEGMetadata()

encodeJPEGMetadata(encodingResult): Promise<Uint8Array>

Encapsulates a Gainmap into a single JPEG file (aka: JPEG-R) with the base map as the sdr visualization and the gainMap encoded into a MPF (Multi-Picture Format) tag.

Parameters

• encodingResult: GainMapMetadata & object

Returns

Promise<Uint8Array>

an Uint8Array representing a JPEG-R file

Example

import { compress, encode, findTextureMinMax } from '@monogrid/gainmap-js'
import { encodeJPEGMetadata } from '@monogrid/gainmap-js/libultrahdr'
import { EXRLoader } from 'three/examples/jsm/loaders/EXRLoader.js'

// load an HDR file
const loader = new EXRLoader()
const image = await loader.loadAsync('image.exr')

// find RAW RGB Max value of a texture
const textureMax = await findTextureMinMax(image)

// Encode the gainmap
const encodingResult = encode({
  image,
  maxContentBoost: Math.max.apply(this, textureMax)
})

// obtain the RAW RGBA SDR buffer and create an ImageData
const sdrImageData = new ImageData(
  encodingResult.sdr.toArray(),
  encodingResult.sdr.width,
  encodingResult.sdr.height
)
// obtain the RAW RGBA Gain map buffer and create an ImageData
const gainMapImageData = new ImageData(
  encodingResult.gainMap.toArray(),
  encodingResult.gainMap.width,
  encodingResult.gainMap.height
)

// parallel compress the RAW buffers into the specified mimeType
const mimeType = 'image/jpeg'
const quality = 0.9

const [sdr, gainMap] = await Promise.all([
  compress({
    source: sdrImageData,
    mimeType,
    quality,
    flipY: true // output needs to be flipped
  }),
  compress({
    source: gainMapImageData,
    mimeType,
    quality,
    flipY: true // output needs to be flipped
  })
])

// obtain the metadata which will be embedded into
// and XMP tag inside the final JPEG file
const metadata = encodingResult.getMetadata()

// embed the compressed images + metadata into a single
// JPEG file
const jpeg = await encodeJPEGMetadata({
  ...encodingResult,
  ...metadata,
  sdr,
  gainMap
})

// `jpeg` will be an `Uint8Array` which can be saved somewhere

Throws

If encodingResult.sdr.mimeType !== 'image/jpeg'

Throws

If encodingResult.gainMap.mimeType !== 'image/jpeg'

Defined in

src/libultrahdr/encode-jpeg-metadata.ts:83