126 lines
4.3 KiB
TypeScript
126 lines
4.3 KiB
TypeScript
import { showLoader, hideLoader, showAlert } from '../ui.js';
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import { downloadFile, readFileAsArrayBuffer, getPDFDocument } from '../utils/helpers.js';
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import { state } from '../state.js';
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import JSZip from 'jszip';
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import * as pdfjsLib from 'pdfjs-dist';
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import { PDFPageProxy } from 'pdfjs-dist';
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pdfjsLib.GlobalWorkerOptions.workerSrc = new URL('pdfjs-dist/build/pdf.worker.min.mjs', import.meta.url).toString();
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const yieldToUI = () => new Promise((r) => setTimeout(r, 0));
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/**
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* Creates a BMP file buffer from raw pixel data (ImageData).
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* This function is self-contained and has no external dependencies.
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* @param {ImageData} imageData The pixel data from a canvas context.
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* @returns {ArrayBuffer} The complete BMP file as an ArrayBuffer.
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*/
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function encodeBMP(imageData: any) {
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const { width, height, data } = imageData;
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const stride = Math.floor((24 * width + 31) / 32) * 4; // Row size must be a multiple of 4 bytes
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const fileSize = stride * height + 54; // 54 byte header
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const buffer = new ArrayBuffer(fileSize);
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const view = new DataView(buffer);
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// BMP File Header (14 bytes)
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view.setUint16(0, 0x4d42, true); // 'BM'
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view.setUint32(2, fileSize, true);
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view.setUint32(10, 54, true); // Offset to pixel data
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// DIB Header (BITMAPINFOHEADER) (40 bytes)
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view.setUint32(14, 40, true); // DIB header size
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view.setUint32(18, width, true);
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view.setUint32(22, -height, true); // Negative height for top-down scanline order
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view.setUint16(26, 1, true); // Color planes
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view.setUint16(28, 24, true); // Bits per pixel
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view.setUint32(30, 0, true); // No compression
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view.setUint32(34, stride * height, true); // Image size
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view.setUint32(38, 2835, true); // Horizontal resolution (72 DPI)
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view.setUint32(42, 2835, true); // Vertical resolution (72 DPI)
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// Pixel Data
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let offset = 54;
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for (let y = 0; y < height; y++) {
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for (let x = 0; x < width; x++) {
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const i = (y * width + x) * 4;
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// BMP is BGR, not RGB
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view.setUint8(offset++, data[i + 2]); // Blue
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view.setUint8(offset++, data[i + 1]); // Green
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view.setUint8(offset++, data[i]); // Red
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}
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// Add padding to make the row a multiple of 4 bytes
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for (let p = 0; p < stride - width * 3; p++) {
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view.setUint8(offset++, 0);
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}
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}
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return buffer;
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}
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export async function pdfToBmp() {
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showLoader('Converting PDF to BMP images...');
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await yieldToUI();
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try {
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const pdf = await getPDFDocument(
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await readFileAsArrayBuffer(state.files[0])
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).promise;
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if(pdf.numPages === 1) {
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showLoader(`Processing the single page...`);
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await yieldToUI();
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const page = await pdf.getPage(1);
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const bmpBuffer = await pageToBlob(page);
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downloadFile(bmpBuffer, getCleanFilename() +'.bmp');
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} else {
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const zip = new JSZip();
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for (let i = 1; i <= pdf.numPages; i++) {
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showLoader(`Processing page ${i} of ${pdf.numPages}...`);
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await yieldToUI();
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const page = await pdf.getPage(i);
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const bmpBuffer = await pageToBlob(page);
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// Add the generated BMP file to the zip archive
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zip.file(`page_${i}.bmp`, bmpBuffer);
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}
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showLoader('Compressing files into a ZIP...');
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await yieldToUI();
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const zipBlob = await zip.generateAsync({ type: 'blob' });
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downloadFile(zipBlob, getCleanFilename() + '_bmps.zip');
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}
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} catch (e) {
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console.error(e);
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showAlert(
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'Error',
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'Failed to convert PDF to BMP. The file might be corrupted.'
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);
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} finally {
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hideLoader();
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}
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}
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async function pageToBlob(page: PDFPageProxy): Promise<Blob> {
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const viewport = page.getViewport({ scale: 1.5 });
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const canvas = document.createElement('canvas');
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const context = canvas.getContext('2d');
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canvas.height = viewport.height;
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canvas.width = viewport.width;
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// Render the PDF page directly to the canvas
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await page.render({ canvasContext: context, viewport: viewport, canvas }).promise;
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// Get the raw pixel data from this canvas
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const imageData = context.getImageData(0, 0, canvas.width, canvas.height);
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// Use our new self-contained function to create the BMP file
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return new Blob([encodeBMP(imageData)]);
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}
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function getCleanFilename(): string {
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let clean = state.files[0].name.replace(/\.pdf$/i, '').trim();
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if (clean.length > 80) {
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clean = clean.slice(0, 80);
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}
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return clean;
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}
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