Add visual workflow builder, fix critical bugs, and add Arabic i18n support
This commit is contained in:
alam00000
304
src/js/utils/ocr.ts
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304
src/js/utils/ocr.ts
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import Tesseract from 'tesseract.js';
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import { PDFDocument, StandardFonts, rgb, PDFFont } from 'pdf-lib';
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import fontkit from '@pdf-lib/fontkit';
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import * as pdfjsLib from 'pdfjs-dist';
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import { getFontForLanguage } from './font-loader.js';
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import { OcrPage, OcrLine } from '@/types';
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import {
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parseHocrDocument,
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calculateWordTransform,
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calculateSpaceTransform,
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} from './hocr-transform.js';
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import { getPDFDocument } from './helpers.js';
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export interface OcrOptions {
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language: string;
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resolution: number;
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binarize: boolean;
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whitelist: string;
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onProgress?: (status: string, progress: number) => void;
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}
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export interface OcrResult {
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pdfBytes: Uint8Array;
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pdfDoc: PDFDocument;
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fullText: string;
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}
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function binarizeCanvas(ctx: CanvasRenderingContext2D) {
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const imageData = ctx.getImageData(0, 0, ctx.canvas.width, ctx.canvas.height);
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const data = imageData.data;
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for (let i = 0; i < data.length; i += 4) {
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const brightness =
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0.299 * data[i] + 0.587 * data[i + 1] + 0.114 * data[i + 2];
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const color = brightness > 128 ? 255 : 0;
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data[i] = data[i + 1] = data[i + 2] = color;
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}
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ctx.putImageData(imageData, 0, 0);
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}
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function drawOcrTextLayer(
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page: ReturnType<typeof PDFDocument.prototype.addPage>,
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ocrPage: OcrPage,
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pageHeight: number,
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primaryFont: PDFFont,
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latinFont: PDFFont
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): void {
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ocrPage.lines.forEach(function (line: OcrLine) {
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const words = line.words;
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for (let i = 0; i < words.length; i++) {
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const word = words[i];
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const text = word.text.replace(
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/[\u0000-\u001F\u007F-\u009F\u200E\u200F\u202A-\u202E\uFEFF]/g,
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''
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);
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if (!text.trim()) continue;
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const hasNonLatin = /[^\u0000-\u007F]/.test(text);
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const font = hasNonLatin ? primaryFont : latinFont;
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if (!font) {
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console.warn('Font not available for text: "' + text + '"');
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continue;
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}
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const transform = calculateWordTransform(
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word,
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line,
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pageHeight,
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(txt: string, size: number) => {
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try {
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return font.widthOfTextAtSize(txt, size);
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} catch {
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return 0;
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}
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}
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);
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if (transform.fontSize <= 0) continue;
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try {
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page.drawText(text, {
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x: transform.x,
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y: transform.y,
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font,
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size: transform.fontSize,
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color: rgb(0, 0, 0),
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opacity: 0,
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});
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} catch (error) {
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console.warn(`Could not draw text "${text}":`, error);
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}
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if (line.injectWordBreaks && i < words.length - 1) {
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const nextWord = words[i + 1];
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const spaceTransform = calculateSpaceTransform(
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word,
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nextWord,
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line,
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pageHeight,
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(size: number) => {
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try {
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return font.widthOfTextAtSize(' ', size);
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} catch {
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return 0;
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}
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}
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);
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if (spaceTransform && spaceTransform.horizontalScale > 0.1) {
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try {
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page.drawText(' ', {
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x: spaceTransform.x,
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y: spaceTransform.y,
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font,
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size: spaceTransform.fontSize,
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color: rgb(0, 0, 0),
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opacity: 0,
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});
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} catch {
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console.warn(`Could not draw space between words`);
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}
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}
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}
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}
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});
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}
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export async function performOcr(
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pdfBytes: Uint8Array | ArrayBuffer,
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options: OcrOptions
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): Promise<OcrResult> {
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const { language, resolution, binarize, whitelist, onProgress } = options;
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const progress = onProgress || (() => {});
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const worker = await Tesseract.createWorker(language, 1, {
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logger: function (m: { status: string; progress: number }) {
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progress(m.status, m.progress || 0);
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},
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});
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await worker.setParameters({
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tessjs_create_hocr: '1',
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tessedit_pageseg_mode: Tesseract.PSM.AUTO,
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});
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if (whitelist) {
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await worker.setParameters({
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tessedit_char_whitelist: whitelist,
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});
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}
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const pdf = await getPDFDocument({ data: pdfBytes }).promise;
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const newPdfDoc = await PDFDocument.create();
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newPdfDoc.registerFontkit(fontkit);
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progress('Loading fonts...', 0);
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const selectedLangs = language.split('+');
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const cjkLangs = ['jpn', 'chi_sim', 'chi_tra', 'kor'];
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const indicLangs = [
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'hin',
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'ben',
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'guj',
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'kan',
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'mal',
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'ori',
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'pan',
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'tam',
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'tel',
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'sin',
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];
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const priorityLangs = [...cjkLangs, ...indicLangs, 'ara', 'rus', 'ukr'];
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const primaryLang =
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selectedLangs.find((l) => priorityLangs.includes(l)) ||
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selectedLangs[0] ||
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'eng';
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const hasCJK = selectedLangs.some((l) => cjkLangs.includes(l));
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const hasIndic = selectedLangs.some((l) => indicLangs.includes(l));
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const hasLatin =
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selectedLangs.some((l) => !priorityLangs.includes(l)) ||
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selectedLangs.includes('eng');
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const isIndicPlusLatin = hasIndic && hasLatin && !hasCJK;
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let primaryFont: PDFFont;
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let latinFont: PDFFont;
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try {
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if (isIndicPlusLatin) {
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const [scriptFontBytes, latinFontBytes] = await Promise.all([
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getFontForLanguage(primaryLang),
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getFontForLanguage('eng'),
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]);
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primaryFont = await newPdfDoc.embedFont(scriptFontBytes, {
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subset: false,
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});
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latinFont = await newPdfDoc.embedFont(latinFontBytes, {
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subset: false,
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});
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} else {
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const fontBytes = await getFontForLanguage(primaryLang);
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primaryFont = await newPdfDoc.embedFont(fontBytes, { subset: false });
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latinFont = primaryFont;
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}
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} catch (e) {
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console.error('Font loading failed, falling back to Helvetica', e);
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primaryFont = await newPdfDoc.embedFont(StandardFonts.Helvetica);
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latinFont = primaryFont;
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}
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let fullText = '';
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try {
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for (let i = 1; i <= pdf.numPages; i++) {
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progress(
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`Processing page ${i} of ${pdf.numPages}`,
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(i - 1) / pdf.numPages
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);
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const page = await pdf.getPage(i);
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const viewport = page.getViewport({ scale: resolution });
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const canvas = document.createElement('canvas');
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canvas.width = viewport.width;
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canvas.height = viewport.height;
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const context = canvas.getContext('2d');
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if (!context) throw new Error('Failed to create canvas context');
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await page.render({ canvasContext: context, viewport, canvas }).promise;
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if (binarize) {
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binarizeCanvas(context);
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}
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const result = await worker.recognize(
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canvas,
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{},
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{ text: true, hocr: true }
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);
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const data = result.data;
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const newPage = newPdfDoc.addPage([viewport.width, viewport.height]);
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const pngImageBytes = await new Promise<Uint8Array>(function (
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resolve,
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reject
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) {
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canvas.toBlob(function (blob) {
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if (!blob) {
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reject(new Error('Failed to create image blob'));
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return;
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}
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const reader = new FileReader();
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reader.onload = function () {
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resolve(new Uint8Array(reader.result as ArrayBuffer));
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};
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reader.onerror = function () {
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reject(new Error('Failed to read image data'));
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};
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reader.readAsArrayBuffer(blob);
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}, 'image/png');
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});
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// Release canvas memory
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canvas.width = 0;
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canvas.height = 0;
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const pngImage = await newPdfDoc.embedPng(pngImageBytes);
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newPage.drawImage(pngImage, {
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x: 0,
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y: 0,
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width: viewport.width,
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height: viewport.height,
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});
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if (data.hocr) {
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const ocrPage = parseHocrDocument(data.hocr);
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drawOcrTextLayer(
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newPage,
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ocrPage,
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viewport.height,
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primaryFont,
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latinFont
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);
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}
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fullText += data.text + '\n\n';
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}
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} finally {
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await worker.terminate();
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}
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const savedBytes = await newPdfDoc.save();
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return {
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pdfBytes: new Uint8Array(savedBytes),
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pdfDoc: newPdfDoc,
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fullText,
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};
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}
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