qrcode-generator-ts/ts/image/GIFImage.ts

Typescript QR Code generator based on https://github.com/kazuhikoarase/qrcode-generator

import { Base64 } from '../io/Base64';
import { OutputStream } from '../io/OutputStream';
import { ByteArrayOutputStream } from '../io/ByteArrayOutputStream';

'use strict';

/**
 * GIF Image (B/W)
 * @author Kazuhiko Arase
 */
export class GIFImage {

  private width: number;
  private height: number;
  private data: number[];

  constructor(width: number, height: number) {
    this.width = width;
    this.height = height;
    var size = width * height;
    this.data = [];
    for (var i = 0; i < size; i += 1) {
      this.data.push(0);
    }
  }

  public setPixel(x: number, y: number, pixel: number): void {
    if (x < 0 || this.width <= x) throw '!' + x;
    if (y < 0 || this.height <= y) throw '!' + y;
    this.data[y * this.width + x] = pixel;
  }

  public getPixel(x: number, y: number): number {
    if (x < 0 || this.width <= x) throw '!' + x;
    if (y < 0 || this.height <= y) throw '!' + y;
    return this.data[y * this.width + x];
  }

  public write(out: OutputStream): void {

    //---------------------------------
    // GIF Signature

    out.writeByte('G'.charCodeAt(0));
    out.writeByte('I'.charCodeAt(0));
    out.writeByte('F'.charCodeAt(0));
    out.writeByte('8'.charCodeAt(0));
    out.writeByte('7'.charCodeAt(0));
    out.writeByte('a'.charCodeAt(0));

    //---------------------------------
    // Screen Descriptor

    this.writeWord(out, this.width);
    this.writeWord(out, this.height);

    out.writeByte(0x80); // 2bit
    out.writeByte(0);
    out.writeByte(0);

    //---------------------------------
    // Global Color Map

    // black
    out.writeByte(0x00);
    out.writeByte(0x00);
    out.writeByte(0x00);

    // white
    out.writeByte(0xff);
    out.writeByte(0xff);
    out.writeByte(0xff);

    //---------------------------------
    // Image Descriptor

    out.writeByte(','.charCodeAt(0));
    this.writeWord(out, 0);
    this.writeWord(out, 0);
    this.writeWord(out, this.width);
    this.writeWord(out, this.height);
    out.writeByte(0);

    //---------------------------------
    // Local Color Map

    //---------------------------------
    // Raster Data

    var lzwMinCodeSize = 2;
    var raster = this.getLZWRaster(lzwMinCodeSize);

    out.writeByte(lzwMinCodeSize);

    var offset: number = 0;

    while (raster.length - offset > 255) {
      out.writeByte(255);
      this.writeBytes(out, raster, offset, 255);
      offset += 255;
    }

    out.writeByte(raster.length - offset);
    this.writeBytes(out, raster, offset, raster.length - offset);
    out.writeByte(0x00);

    //---------------------------------
    // GIF Terminator
    out.writeByte(';'.charCodeAt(0));
  }

  private getLZWRaster(lzwMinCodeSize: number): number[] {

    var clearCode = 1 << lzwMinCodeSize;
    var endCode = (1 << lzwMinCodeSize) + 1;
    var bitLength = lzwMinCodeSize + 1;

    // Setup LZWTable
    var table = new LZWTable();

    for (var i = 0; i < clearCode; i += 1) {
      table.add(String.fromCharCode(i));
    }
    table.add(String.fromCharCode(clearCode));
    table.add(String.fromCharCode(endCode));

    var byteOut = new ByteArrayOutputStream();
    var bitOut = new BitOutputStream(byteOut);

    try {

      // clear code
      bitOut.write(clearCode, bitLength);

      var dataIndex = 0;
      var s = String.fromCharCode(this.data[dataIndex]);
      dataIndex += 1;

      while (dataIndex < this.data.length) {
        var c = String.fromCharCode(this.data[dataIndex]);
        dataIndex += 1;
        if (table.contains(s + c)) {
          s = s + c;
        } else {
          bitOut.write(table.indexOf(s), bitLength);
          if (table.getSize() < 0xfff) {
            if (table.getSize() == (1 << bitLength)) {
              bitLength += 1;
            }
            table.add(s + c);
          }
          s = c;
        }
      }

      bitOut.write(table.indexOf(s), bitLength);

      // end code
      bitOut.write(endCode, bitLength);

    } finally {
      bitOut.close();
    }

    return byteOut.toByteArray();
  }

  private writeWord(out: OutputStream, i: number) {
    out.writeByte(i & 0xff);
    out.writeByte((i >>> 8) & 0xff);
  }

  private writeBytes(
    out: OutputStream,
    bytes: number[], off: number, len: number
  ) {
    for (var i = 0; i < len; i += 1) {
      out.writeByte(bytes[i + off]);
    }
  }

  public toDataURL(): string {
    var bout = new ByteArrayOutputStream();
    this.write(bout);
    bout.close();
    var s = '';
    var bytes = Base64.encode(bout.toByteArray());
    for (var i = 0; i < bytes.length; i += 1) {
      s += String.fromCharCode(bytes[i]);
    }
    return 'data:image/gif;base64,' + s;
  }
}

class LZWTable {

  private map: { [key: string]: number; } = {};
  private size: number = 0;

  constructor() {
  }

  public add(key: string): void {
    if (this.contains(key)) {
      throw 'dup key:' + key;
    }
    this.map[key] = this.size;
    this.size += 1;
  }

  public getSize(): number {
    return this.size;
  }

  public indexOf(key: string): number {
    return this.map[key];
  }

  public contains(key: string): boolean {
    return typeof this.map[key] != 'undefined';
  }
}

class BitOutputStream {

  private out: OutputStream;
  private bitLength: number;
  private bitBuffer: number;

  constructor(out: OutputStream) {
    this.out = out;
    this.bitLength = 0;
  }

  public write(data: number, length: number): void {

    if ((data >>> length) != 0) {
      throw 'length over';
    }

    while (this.bitLength + length >= 8) {
      this.out.writeByte(0xff &
        ((data << this.bitLength) | this.bitBuffer));
      length -= (8 - this.bitLength);
      data >>>= (8 - this.bitLength);
      this.bitBuffer = 0;
      this.bitLength = 0;
    }

    this.bitBuffer = (data << this.bitLength) | this.bitBuffer;
    this.bitLength = this.bitLength + length;
  }

  public flush(): void {
    if (this.bitLength > 0) {
      this.out.writeByte(this.bitBuffer);
    }
    this.out.flush();
  }

  public close(): void {
    this.flush();
    this.out.close();
  }
}