add text encoder/decoder options

Author: voliva

README.md

@@ -65,6 +65,7 @@ const larger = encodeQR(txt, 'gif', { scale: 4 });
 // type QrOpts = {
 //   ecc?: 'low' | 'medium' | 'quartile' | 'high';
 //   encoding?: 'numeric' | 'alphanumeric' | 'byte' | 'kanji' | 'eci';
+//   textEncoder?: (text: string) => Uint8Array;
 //   version?: number; // 1..40, QR code version
 //   mask?: number; // 0..7, mask number
 //   border?: number; // Border size, default 2.

src/decode.ts

@@ -738,8 +738,11 @@ function parseInfo(b: Bitmap) {
 // Global symbols in both browsers and Node.js since v11
 // See https://github.com/microsoft/TypeScript/issues/31535
 declare const TextDecoder: any;
+function bytesToUtf8(bytes: Uint8Array): string {
+  return new TextDecoder().decode(new Uint8Array(bytes));
+}
 
-function decodeBitmap(b: Bitmap): string {
+function decodeBitmap(b: Bitmap, decoder: (bytes: Uint8Array) => string = bytesToUtf8): string {
   const size = b.height;
   if (size < 21 || (size & 0b11) !== 1 || size !== b.width)
     throw new Error(`decode: invalid size=${size}`);
@@ -815,14 +818,15 @@ function decodeBitmap(b: Bitmap): string {
     } else if (mode === 'byte') {
       let utf8 = [];
       for (let i = 0; i < count; i++) utf8.push(Number(`0b${readBits(8)}`));
-      res += new TextDecoder().decode(new Uint8Array(utf8));
+      res += decoder(new Uint8Array(utf8));
     } else throw new Error(`Unknown mode=${mode}`);
   }
   return res;
 }
 
 export type DecodeOpts = {
   cropToSquare?: boolean;
+  textDecoder?: (bytes: Uint8Array) => string;
   pointsOnDetect?: (points: FinderPoints) => void;
   imageOnBitmap?: (img: Image) => void;
   imageOnDetect?: (img: Image) => void;
@@ -876,7 +880,7 @@ export function decodeQR(img: Image, opts: DecodeOpts = {}): string {
     opts.pointsOnDetect(p);
   }
   if (opts.imageOnDetect) opts.imageOnDetect(bits.toImage());
-  const res = decodeBitmap(bits);
+  const res = decodeBitmap(bits, opts.textDecoder);
   if (opts.imageOnResult) opts.imageOnResult(bits.toImage());
   return res;
 }

src/index.ts

@@ -901,7 +901,13 @@ export function utf8ToBytes(str: string): Uint8Array {
   return new Uint8Array(new TextEncoder().encode(str)); // https://bugzil.la/1681809
 }
 
-function encode(ver: Version, ecc: ErrorCorrection, data: string, type: EncodingType): Uint8Array {
+function encode(
+  ver: Version,
+  ecc: ErrorCorrection,
+  data: string,
+  type: EncodingType,
+  encoder: (value: string) => Uint8Array = utf8ToBytes
+): Uint8Array {
   let encoded = '';
   let dataLen = data.length;
   if (type === 'numeric') {
@@ -919,7 +925,7 @@ function encode(ver: Version, ecc: ErrorCorrection, data: string, type: Encoding
     for (let i = 0; i < n - 1; i += 2) encoded += bin(t[i] * 45 + t[i + 1], 11);
     if (n % 2 == 1) encoded += bin(t[n - 1], 6); // pad if odd number of chars
   } else if (type === 'byte') {
-    const utf8 = utf8ToBytes(data);
+    const utf8 = encoder(data);
     dataLen = utf8.length;
     encoded = Array.from(utf8)
       .map((i) => bin(i, 8))
@@ -1041,6 +1047,7 @@ function drawQRBest(ver: Version, ecc: ErrorCorrection, data: Uint8Array, maskId
 export type QrOpts = {
   ecc?: ErrorCorrection | undefined;
   encoding?: EncodingType | undefined;
+  textEncoder?: (text: string) => Uint8Array;
   version?: Version | undefined;
   mask?: number | undefined;
   border?: number | undefined;
@@ -1112,13 +1119,13 @@ export function encodeQR(text: string, output: Output = 'raw', opts: QrOpts & Sv
     err = new Error('Unknown error');
   if (ver !== undefined) {
     validateVersion(ver);
-    data = encode(ver, ecc, text, encoding);
+    data = encode(ver, ecc, text, encoding, opts.textEncoder);
   } else {
     // If no version is provided, try to find smallest one which fits
     // Currently just scans all version, can be significantly speedup if needed
     for (let i = 1; i <= 40; i++) {
       try {
-        data = encode(i, ecc, text, encoding);
+        data = encode(i, ecc, text, encoding, opts.textEncoder);
         ver = i;
         break;
       } catch (e) {