qoijs

"Quite-OK Image format" encoder/decoder in vanilla javascript.

Installing

With npm do:

npm install qoijs

With yarn do:

yarn add qoijs

A compiled version for web browsers is also available on a CDN:

<script src="https://cdn.jsdelivr.net/gh/kchapelier/qoijs@1.0.0/build/qoijs.min.js"></script>

Public API

Functions

decode(arrayBuffer[, byteOffset[, byteLength[, outputChannels]]])

Decode a QOI file given as an ArrayBuffer.

Returns a literal containing the color data as a TypedArray and all the metadata of the image.

• arrayBuffer: ArrayBuffer containing the QOI file.
• byteOffset: Offset to the start of the QOI file in arrayBuffer, defaults to the 0.
• byteLength: Length of the QOI file in bytes, defaults to the remaining length of arrayBuffer after byteOffset.
• outputChannels: Number of channels to include in the decoded array (used to remove or add the alpha channel), defaults to the number of channels contained in the QOI file.

const QOI = require('qoijs');

// using fs in node to read the content of a file as a Buffer
const buffer = require('fs').readFileSync('some_image.qoi');
const decodedData = QOI.decode(buffer.buffer, buffer.byteOffset, buffer.byteLength);

// using FileReader to read a file retrieved from a drop event as an ArrayBuffer
const reader = new FileReader();
reader.readAsArrayBuffer(file);
reader.onloadend = function () {
    const arrayBuffer = reader.result;
    const decodedData = QOI.decode(arrayBuffer);
};

encode(colorData, description)

Encode a QOI file.

Returns an ArrayBuffer containing the QOI file content.

• colorData: Flat array containing the color information for each pixel of the image (from left to right, top to bottom). Must be either an instance of Uint8Array or Uint8ClampedArray.
• description:
  • width: The width of the image.
  • height: The height of the image.
  • channels: The number of channels of the image.
    • 3: RGB, 4: RGBA
  • colorspace: The color space used to encode the colors in colorData.
    • 0: sRGB with linear alpha, 1: linear

const QOI = require('qoijs');

// encode a 2x2 b/w checkerboard pattern from an arbitrary colorData array
const colorData = new Uint8Array([0,0,0,255, 255,255,255,255, 255,255,255,255, 0,0,0,0]);
const arrayBuffer = QOI.encode(colorData, {
    width: 2,
    height: 2,
    channels: 4,
    colorspace: 0
});

// encode the content of a 2D canvas (ImageData)
const imageData = canvasContext.getImageData(0, 0, canvas.width, canvas.height);
const arrayBuffer = QOI.encode(imageData.data, {
    width: imageData.width,
    height: imageData.height,
    channels: 4,
    colorspace: 0
});

History

1.0.0 (2021-12-27) :

• First release

How to contribute ?

For new features and other enhancements, please make sure to contact me beforehand, either on Twitter or through an issue on Github.

License

MIT