lujx1024 / nodle-i-ching

IChing-JS

An IChing encoding and decoding library written in typescript for use in javascript-based web apps.

Installation

Clone the repository and run npm install --no-save followed by npm run build.

Node.js

The Node.js files can be found in ./lib/esm5 after building.

Javascript

This library can be used in javascript by including ./lib/umd/index.min.js as script source.

Usage

Encoding

IChing-JS library exports a method iching.encode(payload, options?).

Arguments

• payload - A string of alphanumeric characters that is the desired payload of the IChing.
• options (optional) - Additional options:
  • ecLevel - Error correction level, a number between 0 and 1 representing the maximum percentage of errors that can be corrected, relative to the payload length. Defaults to Encoder.EC_MEDIUM (0.15).
  • resolution - A number representing the width and height of the square image produced by the method. Defaults to 1250.
  • roundEdges - A boolean determining whether the symbols' edges in the output image are straight or round. Defaults to false, which means straight edges.
  • inverted - A boolean determining whether the output image is inverted, i.e. white on black instead of black on white. Defaults to false.

Return Value

If the encoding process succeeds, the method will return an object that implements the EncodedIChing interface.

Example

Example usage with options specified:

const payload = "thisisanexample123";
const options = { ecLevel: 0.5, resolution: 2000, roundEdges: true, inverted: false };
const encoded = iching.encode(payload, options);

Or without options:

const payload = "thisisanexample123";
const encoded = iching.encode(payload);

Which is equivalent to:

const payload = "thisisanexample123";
const defaultOptions = { ecLevel: 0.15, resolution: 1250, roundEdges: false, inevrted: false };
const encoded = iching.encode(payload, defaultOptions);

Image can be displayed using HTML canvas:

// 'cvs' and 'ctx' are an HTML canvas element, and its 2D rendering context, respectively.
const imgData = encoded.imageData;
cvs.width = imgData.width;
cvs.height = imgData.height;
const ctxImgData = new ImageData(imgData.data, imgData.width, imgData.height);
ctx.putImageData(ctxImgData, 0, 0);

// If 'img' is an HTML image element, its 'src' attribute can be set like follows:
img.src = cvs.toDataURL();

Decoding

IChing-JS library exports a method iching.decode(imageData, width, height).

Arguments

• imageData - A Uint8ClampedArray of RGBA pixel values in the form [r0, g0, b0, a0, r1, g1, b1, a1, ...]. The length of this array should be 4 * width * height.
• width - The width of the image to be decoded.
• height - The height of the image to be decoded.

Return value

If the decoding process succeeds, the method will return an object that implements the DecodedIChing interface.

Example

Example usage:

// Let 'width' and 'height' be the width and height of the input image, respectively,
// and 'imageData' be a Uint8ClampedArray of RGBA pixel values, and of length 4 * width * height.
const decoded = iching.decode(imageData, width, height);
console.log(decoded.version, decoded.size);
console.log(decoded.data);

Documentation

Detailed HTML docs can be found here.

License

IChing-JS is released under the GPLv3 license.
Copyright © Nodle