@li0ard/tsemrtd/dist/dg4.js

simple library for eMRTD. supports browsers, node, bun and more!

import { TLV } from "@li0ard/tinytlv";
import { Enums, Interfaces, Schemas, Utils } from "./index";
import { AsnConvert } from "@peculiar/asn1-schema";
/**
 * Class for working with DG4 (Iris)
 * @hideconstructor
 * @experimental
*/
export class DG4 {
    /**
     * Extract int from Uint8Array
     * @hidden
     * @param data Uint8Array
     * @param start Offset
     * @param end Offset+length
     */
    extractContent(data, start, end) {
        if (end - start === 1) {
            return data[start];
        }
        else if (end - start < 4) {
            return (data[start] << 8) | data[start + 1];
        }
        else if (end - start == 4) {
            return (data[start] << 24) | (data[start + 1] << 16) | (data[start + 2] << 8) | data[start + 3];
        }
        return parseInt(Utils.bytesToHex(data.slice(start, end)), 16);
    }
    /**
     * Read Biometric data block
     * @param tlv
     */
    readBDB(tlv) {
        if (parseInt(tlv.tag, 16) != 0x7f60)
            throw new Error(`Invalid object tag "0x${tlv.tag}", expected 0x7f60`);
        let sbh = AsnConvert.parse(tlv.childs[0].toBytes(), Schemas.SBH);
        let firstBlock = tlv.childs[1];
        if (parseInt(firstBlock.tag, 16) != 0x5f2e && parseInt(firstBlock.tag, 16) != 0x7f2e)
            throw new Error(`Invalid object tag "0x${tlv.tag}", expected 0x5f2e or 0x7f2e`);
        let data = firstBlock.byteValue;
        if (this.extractContent(data, 0, 4) != 0x49495200)
            throw new Error("Biometric data block is invalid");
        let offset = 4;
        if (this.extractContent(data, offset, offset + 4) != 0x30313000)
            throw new Error("Version of Biometric data is not valid");
        offset += 4;
        let lengthOfRecord = this.extractContent(data, offset, offset + 4);
        offset += 4;
        //let dataLength = lengthOfRecord - 45;
        let captureDeviceId = this.extractContent(data, offset, offset + 2);
        offset += 2;
        let count = this.extractContent(data, offset, offset + 1);
        offset += 1;
        if (count > 1)
            console.warn("[DG4] The record contains more than 1 image.");
        let recordHeaderLength = this.extractContent(data, offset, offset + 2);
        offset += 2;
        if (recordHeaderLength != 45)
            throw new Error(`Expected header length 45, found ${recordHeaderLength}`);
        let imagePropertiesBits = this.extractContent(data, offset, offset + 2);
        offset += 2;
        let irisDiameter = this.extractContent(data, offset, offset + 2);
        offset += 2;
        let imageType = this.extractContent(data, offset, offset + 2);
        offset += 2;
        let imageWidth = this.extractContent(data, offset, offset + 2);
        offset += 2;
        let imageHeight = this.extractContent(data, offset, offset + 2);
        offset += 2;
        let depth = this.extractContent(data, offset, offset + 1);
        offset += 1;
        let imageTransformation = this.extractContent(data, offset, offset + 1);
        offset += 1;
        let deviceUniqueId = this.extractContent(data, offset, offset + 16);
        offset += 16;
        let biometricSubtype = this.extractContent(data, offset, offset + 1);
        offset += 1;
        let biometricSubtypeCount = this.extractContent(data, offset, offset + 2);
        offset += 2;
        if (biometricSubtypeCount > 1)
            console.warn("[DG4] The record contains more than 1 image.");
        let imageNumber = this.extractContent(data, offset, offset + 2);
        offset += 2;
        let quality = this.extractContent(data, offset, offset + 1);
        offset += 1;
        let rotationAngle = this.extractContent(data, offset, offset + 2);
        offset += 2;
        let rotationAngleUncertainty = this.extractContent(data, offset, offset + 2);
        offset += 2;
        let imageEnd = this.extractContent(data, offset, offset + 4) & 4294967295;
        offset += 4;
        let imageData = data.subarray(offset, offset + imageEnd);
        return {
            sbh,
            lengthOfRecord,
            captureDeviceId,
            imagePropertiesBits,
            irisDiameter,
            imageType,
            imageWidth,
            imageHeight,
            depth,
            imageTransformation,
            deviceUniqueId,
            biometricSubtype,
            quality,
            rotationAngle,
            rotationAngleUncertainty,
            imageData
        };
    }
    /**
     * Get image of eye iris
     * @param data Data of EF.DG4 file
     */
    static load(data) {
        let tlv = TLV.parse(data);
        if (parseInt(tlv.tag, 16) != Enums.TAGS.DG4)
            throw new Error(`Invalid DG4 tag "0x${tlv.tag}", expected 0x${Enums.TAGS.DG4.toString(16)}`);
        let bigt = tlv.childs[0];
        if (parseInt(bigt.tag, 16) != 0x7f61)
            throw new Error(`Invalid object tag "0x${bigt.tag}", expected 0x7f61`);
        let bict = bigt.childs[0];
        if (parseInt(bict.tag, 16) != 0x02)
            throw new Error(`Invalid object tag "0x${bict.tag}", expected 0x02`);
        let bitCount = parseInt(bigt.childs[0].value, 16);
        let results = [];
        for (let i = 0; i < bitCount; i++) {
            results.push(new DG4().readBDB(bigt.childs[i + 1]));
        }
        return results;
    }
}