75 lines
2.1 KiB
JavaScript
75 lines
2.1 KiB
JavaScript
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/**
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* Browser-side Tesseract OCR for Layer-1 card name strip recognition.
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* Uses tesseract.js workers (off main thread). Language data loads from CDN on first use.
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*/
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let workerPromise = null;
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async function getWorker() {
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if (!workerPromise) {
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workerPromise = (async () => {
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const { createWorker } = await import('tesseract.js');
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const worker = await createWorker('eng', 1, {
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logger: () => {},
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});
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await worker.setParameters({
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tessedit_pageseg_mode: '6',
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});
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return worker;
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})();
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}
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return workerPromise;
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}
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function cropNameStrip(imageDataUrl) {
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return new Promise((resolve, reject) => {
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const img = new Image();
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img.onload = () => {
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const stripHeight = Math.max(1, Math.floor(img.height * 0.35));
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const canvas = document.createElement('canvas');
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canvas.width = img.width;
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canvas.height = stripHeight;
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const ctx = canvas.getContext('2d');
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ctx.drawImage(img, 0, 0, img.width, stripHeight, 0, 0, img.width, stripHeight);
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resolve(canvas.toDataURL('image/jpeg', 0.92));
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};
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img.onerror = () => reject(new Error('Failed to load image for OCR'));
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img.src = imageDataUrl;
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});
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}
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/**
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* OCR the top name strip of a card crop.
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* @param {string} imageDataUrl - full card crop data URL
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* @returns {Promise<{ text: string, confidence: number }>}
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*/
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export async function recognizeCardNameStrip(imageDataUrl) {
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if (typeof window === 'undefined') {
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return { text: '', confidence: 0 };
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}
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try {
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const stripUrl = await cropNameStrip(imageDataUrl);
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const worker = await getWorker();
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const { data } = await worker.recognize(stripUrl);
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return {
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text: (data.text || '').trim(),
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confidence: Math.round(data.confidence || 0),
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};
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} catch (error) {
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console.warn('[ocr-worker] recognizeCardNameStrip failed:', error);
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return { text: '', confidence: 0 };
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}
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}
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export async function terminateOcrWorker() {
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if (!workerPromise) return;
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try {
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const worker = await workerPromise;
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await worker.terminate();
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} catch {
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// ignore teardown errors
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}
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workerPromise = null;
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}
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