@abasb75/jpeg-lossless-decoder/quantization-table.js

A JavaScript JPEG Lossless decoder.

import { createArray } from './utils';
var QuantizationTable = /** @class */ (function () {
    function QuantizationTable() {
        Object.defineProperty(this, "precision", {
            enumerable: true,
            configurable: true,
            writable: true,
            value: []
        }); // Quantization precision 8 or 16
        Object.defineProperty(this, "tq", {
            enumerable: true,
            configurable: true,
            writable: true,
            value: [0, 0, 0, 0]
        }); // 1: this table is presented
        Object.defineProperty(this, "quantTables", {
            enumerable: true,
            configurable: true,
            writable: true,
            value: createArray(4, 64)
        }); // Tables
    }
    Object.defineProperty(QuantizationTable.prototype, "read", {
        enumerable: false,
        configurable: true,
        writable: true,
        value: function (data, table) {
            var count = 0;
            var temp;
            var t;
            var i;
            var length = data.get16();
            count += 2;
            while (count < length) {
                temp = data.get8();
                count += 1;
                t = temp & 0x0f;
                if (t > 3) {
                    throw new Error('ERROR: Quantization table ID > 3');
                }
                this.precision[t] = temp >> 4;
                if (this.precision[t] === 0) {
                    this.precision[t] = 8;
                }
                else if (this.precision[t] === 1) {
                    this.precision[t] = 16;
                }
                else {
                    throw new Error('ERROR: Quantization table precision error');
                }
                this.tq[t] = 1;
                if (this.precision[t] === 8) {
                    for (i = 0; i < 64; i += 1) {
                        if (count > length) {
                            throw new Error('ERROR: Quantization table format error');
                        }
                        this.quantTables[t][i] = data.get8();
                        count += 1;
                    }
                    QuantizationTable.enhanceQuantizationTable(this.quantTables[t], table);
                }
                else {
                    for (i = 0; i < 64; i += 1) {
                        if (count > length) {
                            throw new Error('ERROR: Quantization table format error');
                        }
                        this.quantTables[t][i] = data.get16();
                        count += 2;
                    }
                    QuantizationTable.enhanceQuantizationTable(this.quantTables[t], table);
                }
            }
            if (count !== length) {
                throw new Error('ERROR: Quantization table error [count!=Lq]');
            }
            return 1;
        }
    });
    Object.defineProperty(QuantizationTable, "enhanceQuantizationTable", {
        enumerable: true,
        configurable: true,
        writable: true,
        value: function (qtab, table) {
            for (var i = 0; i < 8; i += 1) {
                qtab[table[0 * 8 + i]] *= 90;
                qtab[table[4 * 8 + i]] *= 90;
                qtab[table[2 * 8 + i]] *= 118;
                qtab[table[6 * 8 + i]] *= 49;
                qtab[table[5 * 8 + i]] *= 71;
                qtab[table[1 * 8 + i]] *= 126;
                qtab[table[7 * 8 + i]] *= 25;
                qtab[table[3 * 8 + i]] *= 106;
            }
            for (var i = 0; i < 8; i += 1) {
                qtab[table[0 + 8 * i]] *= 90;
                qtab[table[4 + 8 * i]] *= 90;
                qtab[table[2 + 8 * i]] *= 118;
                qtab[table[6 + 8 * i]] *= 49;
                qtab[table[5 + 8 * i]] *= 71;
                qtab[table[1 + 8 * i]] *= 126;
                qtab[table[7 + 8 * i]] *= 25;
                qtab[table[3 + 8 * i]] *= 106;
            }
            for (var i = 0; i < 64; i += 1) {
                qtab[i] >>= 6;
            }
        }
    });
    return QuantizationTable;
}());
export { QuantizationTable };