@nuintun/qrcode/esm/common/image/GIFImage.js

A pure JavaScript QRCode encode and decode library.

/**
 * @module QRCode
 * @package @nuintun/qrcode
 * @license MIT
 * @version 5.0.2
 * @author nuintun <nuintun@qq.com>
 * @description A pure JavaScript QRCode encode and decode library.
 * @see https://github.com/nuintun/qrcode#readme
 */

import { compress } from './utils/lzw/index.js';
import { ByteStream } from './utils/ByteStream.js';
import { Base64Stream, fromCharCode } from './utils/Base64Stream.js';

/**
 * @module GIFImage
 */
class GIFImage {
  #width;
  #height;
  #foreground;
  #background;
  #pixels = [];
  constructor(width, height, { foreground = [0x00, 0x00, 0x00], background = [0xff, 0xff, 0xff] } = {}) {
    this.#width = width;
    this.#height = height;
    this.#foreground = foreground;
    this.#background = background;
  }
  #encode() {
    const width = this.#width;
    const height = this.#height;
    const stream = new ByteStream();
    const background = this.#background;
    const foreground = this.#foreground;
    // GIF signature: GIF89a.
    stream.writeBytes([0x47, 0x49, 0x46, 0x38, 0x39, 0x61]);
    // Logical screen descriptor.
    stream.writeInt16(width);
    stream.writeInt16(height);
    stream.writeBytes([0x80, 0, 0]);
    // Global background color palette.
    stream.writeBytes([background[0], background[1], background[2]]);
    // Global foreground color palette.
    stream.writeBytes([foreground[0], foreground[1], foreground[2]]);
    // Image descriptor.
    stream.writeByte(0x2c);
    stream.writeInt16(0);
    stream.writeInt16(0);
    stream.writeInt16(width);
    stream.writeInt16(height);
    stream.writeByte(0);
    // Compress pixels to stream.
    compress(this.#pixels, 2, stream);
    // GIF terminator.
    stream.writeByte(0x3b);
    return stream.bytes;
  }
  set(x, y, color) {
    this.#pixels[y * this.#width + x] = color;
  }
  toDataURL() {
    const bytes = this.#encode();
    const stream = new Base64Stream();
    for (const byte of bytes) {
      stream.write(byte);
    }
    stream.close();
    const base64 = stream.bytes;
    let url = 'data:image/gif;base64,';
    for (const byte of base64) {
      url += fromCharCode(byte);
    }
    return url;
  }
}

export { GIFImage };