372 lines
13 KiB
Dart
372 lines
13 KiB
Dart
import 'dart:io';
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import 'dart:typed_data';
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import 'package:flutter/rendering.dart';
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import 'package:flutter/widgets.dart';
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import 'package:pdf/widgets.dart' as pw;
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import 'package:pdf/pdf.dart' as pdf;
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import 'package:printing/printing.dart' as printing;
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import 'package:image/image.dart' as img;
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// NOTE:
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// - This exporter uses a raster snapshot of the UI (RepaintBoundary) and embeds it into a new PDF.
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// - It does NOT perform vector-accurate stamping into the source PDF.
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// - Vector stamping remains unimplemented with FOSS-only constraints because the `pdf` package
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// cannot import/modify existing PDF pages. If/when a suitable FOSS library exists, wire it here.
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class ExportService {
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/// Compose a new PDF by rasterizing the original PDF pages (via pdfrx engine)
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/// and optionally stamping a signature image on the specified page.
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///
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/// Inputs:
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/// - [inputPath]: Path to the original PDF to read
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/// - [outputPath]: Path to write the composed PDF
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/// - [signedPage]: 1-based page index to place the signature on (null = no overlay)
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/// - [signatureRectUi]: Rect in the UI's logical page space (e.g. 400x560)
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/// - [uiPageSize]: The logical page size used by the UI layout (SignatureController.pageSize)
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/// - [signatureImageBytes]: PNG/JPEG bytes of the signature image to overlay
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/// - [targetDpi]: Rasterization DPI for background pages
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Future<bool> exportSignedPdfFromFile({
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required String inputPath,
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required String outputPath,
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required int? signedPage,
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required Rect? signatureRectUi,
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required Size uiPageSize,
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required Uint8List? signatureImageBytes,
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Map<int, List<Rect>>? placementsByPage,
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Map<int, List<String>>? placementImageByPage,
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Map<String, Uint8List>? libraryBytes,
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double targetDpi = 144.0,
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}) async {
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// print(
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// 'exportSignedPdfFromFile: enter signedPage=$signedPage outputPath=$outputPath',
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// );
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// Read source bytes and delegate to bytes-based exporter
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Uint8List? srcBytes;
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try {
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srcBytes = await File(inputPath).readAsBytes();
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} catch (_) {
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srcBytes = null;
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}
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if (srcBytes == null) return false;
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final bytes = await exportSignedPdfFromBytes(
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srcBytes: srcBytes,
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signedPage: signedPage,
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signatureRectUi: signatureRectUi,
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uiPageSize: uiPageSize,
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signatureImageBytes: signatureImageBytes,
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placementsByPage: placementsByPage,
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placementImageByPage: placementImageByPage,
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libraryBytes: libraryBytes,
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targetDpi: targetDpi,
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);
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if (bytes == null) return false;
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try {
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final file = File(outputPath);
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await file.writeAsBytes(bytes, flush: true);
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return true;
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} catch (_) {
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return false;
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}
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}
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/// Compose a new PDF from source PDF bytes; returns the resulting PDF bytes.
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Future<Uint8List?> exportSignedPdfFromBytes({
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required Uint8List srcBytes,
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required int? signedPage,
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required Rect? signatureRectUi,
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required Size uiPageSize,
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required Uint8List? signatureImageBytes,
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Map<int, List<Rect>>? placementsByPage,
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Map<int, List<String>>? placementImageByPage,
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Map<String, Uint8List>? libraryBytes,
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double targetDpi = 144.0,
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}) async {
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final out = pw.Document(version: pdf.PdfVersion.pdf_1_4, compress: false);
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int pageIndex = 0;
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bool anyPage = false;
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try {
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await for (final raster in printing.Printing.raster(
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srcBytes,
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dpi: targetDpi,
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)) {
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anyPage = true;
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pageIndex++;
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final widthPx = raster.width;
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final heightPx = raster.height;
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final widthPts = widthPx * 72.0 / targetDpi;
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final heightPts = heightPx * 72.0 / targetDpi;
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final bgPng = await raster.toPng();
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final bgImg = pw.MemoryImage(bgPng);
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pw.MemoryImage? sigImgObj;
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final hasMulti =
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(placementsByPage != null && placementsByPage.isNotEmpty);
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final pagePlacements =
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hasMulti
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? (placementsByPage[pageIndex] ?? const <Rect>[])
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: const <Rect>[];
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final pageImageIds =
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hasMulti
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? (placementImageByPage?[pageIndex] ?? const <String>[])
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: const <String>[];
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final shouldStampSingle =
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!hasMulti &&
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signedPage != null &&
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pageIndex == signedPage &&
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signatureRectUi != null &&
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signatureImageBytes != null &&
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signatureImageBytes.isNotEmpty;
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if (shouldStampSingle) {
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try {
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sigImgObj = pw.MemoryImage(signatureImageBytes);
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} catch (_) {
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sigImgObj = null;
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}
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}
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out.addPage(
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pw.Page(
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pageTheme: pw.PageTheme(
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margin: pw.EdgeInsets.zero,
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pageFormat: pdf.PdfPageFormat(widthPts, heightPts),
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),
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build: (ctx) {
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final children = <pw.Widget>[
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pw.Positioned(
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left: 0,
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top: 0,
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child: pw.Image(
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bgImg,
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width: widthPts,
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height: heightPts,
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fit: pw.BoxFit.fill,
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),
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),
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];
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// Multi-placement stamping: per-placement image from libraryBytes
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if (hasMulti && pagePlacements.isNotEmpty) {
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for (var i = 0; i < pagePlacements.length; i++) {
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final r = pagePlacements[i];
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final left = r.left / uiPageSize.width * widthPts;
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final top = r.top / uiPageSize.height * heightPts;
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final w = r.width / uiPageSize.width * widthPts;
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final h = r.height / uiPageSize.height * heightPts;
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Uint8List? bytes;
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if (i < pageImageIds.length) {
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final id = pageImageIds[i];
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bytes = libraryBytes?[id];
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}
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bytes ??=
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signatureImageBytes; // fallback to single image if provided
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if (bytes != null && bytes.isNotEmpty) {
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pw.MemoryImage? imgObj;
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try {
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imgObj = pw.MemoryImage(bytes);
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} catch (_) {
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imgObj = null;
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}
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if (imgObj != null) {
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children.add(
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pw.Positioned(
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left: left,
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top: top,
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child: pw.SizedBox(
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width: w,
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height: h,
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child: pw.FittedBox(
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fit: pw.BoxFit.contain,
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child: pw.Image(imgObj),
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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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}
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} else if (shouldStampSingle && sigImgObj != null) {
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final r = signatureRectUi;
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final left = r.left / uiPageSize.width * widthPts;
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final top = r.top / uiPageSize.height * heightPts;
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final w = r.width / uiPageSize.width * widthPts;
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final h = r.height / uiPageSize.height * heightPts;
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children.add(
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pw.Positioned(
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left: left,
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top: top,
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child: pw.SizedBox(
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width: w,
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height: h,
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child: pw.FittedBox(
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fit: pw.BoxFit.contain,
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child: pw.Image(sigImgObj),
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),
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),
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),
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);
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}
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return pw.Stack(children: children);
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},
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),
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);
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}
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} catch (e) {
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anyPage = false;
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}
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if (!anyPage) {
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// Fallback as A4 blank page with optional signature
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final widthPts = pdf.PdfPageFormat.a4.width;
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final heightPts = pdf.PdfPageFormat.a4.height;
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pw.MemoryImage? sigImgObj;
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final hasMulti =
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(placementsByPage != null && placementsByPage.isNotEmpty);
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final pagePlacements =
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hasMulti ? (placementsByPage[1] ?? const <Rect>[]) : const <Rect>[];
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final pageImageIds =
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hasMulti
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? (placementImageByPage?[1] ?? const <String>[])
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: const <String>[];
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final shouldStampSingle =
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!hasMulti &&
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signedPage != null &&
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signedPage == 1 &&
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signatureRectUi != null &&
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signatureImageBytes != null &&
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signatureImageBytes.isNotEmpty;
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if (shouldStampSingle) {
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try {
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// If it's already PNG, keep as-is to preserve alpha; otherwise decode/encode PNG
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final asStr = String.fromCharCodes(signatureImageBytes.take(8));
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final isPng =
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signatureImageBytes.length > 8 &&
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signatureImageBytes[0] == 0x89 &&
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asStr.startsWith('\u0089PNG');
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if (isPng) {
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sigImgObj = pw.MemoryImage(signatureImageBytes);
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} else {
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final decoded = img.decodeImage(signatureImageBytes);
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if (decoded != null) {
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final png = img.encodePng(decoded, level: 6);
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sigImgObj = pw.MemoryImage(Uint8List.fromList(png));
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}
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}
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} catch (_) {}
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}
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out.addPage(
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pw.Page(
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pageTheme: pw.PageTheme(
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margin: pw.EdgeInsets.zero,
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pageFormat: pdf.PdfPageFormat(widthPts, heightPts),
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),
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build: (ctx) {
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final children = <pw.Widget>[
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pw.Container(
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width: widthPts,
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height: heightPts,
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color: pdf.PdfColors.white,
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),
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];
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// Multi-placement stamping on fallback page
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if (hasMulti && pagePlacements.isNotEmpty) {
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for (var i = 0; i < pagePlacements.length; i++) {
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final r = pagePlacements[i];
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final left = r.left / uiPageSize.width * widthPts;
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final top = r.top / uiPageSize.height * heightPts;
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final w = r.width / uiPageSize.width * widthPts;
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final h = r.height / uiPageSize.height * heightPts;
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Uint8List? bytes;
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if (i < pageImageIds.length) {
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final id = pageImageIds[i];
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bytes = libraryBytes?[id];
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}
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bytes ??=
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signatureImageBytes; // fallback to single image if provided
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if (bytes != null && bytes.isNotEmpty) {
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pw.MemoryImage? imgObj;
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try {
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// Ensure PNG for transparency if not already
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final asStr = String.fromCharCodes(bytes.take(8));
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final isPng =
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bytes.length > 8 &&
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bytes[0] == 0x89 &&
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asStr.startsWith('\u0089PNG');
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if (isPng) {
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imgObj = pw.MemoryImage(bytes);
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} else {
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final decoded = img.decodeImage(bytes);
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if (decoded != null) {
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final png = img.encodePng(decoded, level: 6);
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imgObj = pw.MemoryImage(Uint8List.fromList(png));
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}
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}
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} catch (_) {
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imgObj = null;
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}
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if (imgObj != null) {
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children.add(
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pw.Positioned(
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left: left,
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top: top,
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child: pw.SizedBox(
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width: w,
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height: h,
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child: pw.FittedBox(
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fit: pw.BoxFit.contain,
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child: pw.Image(imgObj),
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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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}
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} else if (shouldStampSingle && sigImgObj != null) {
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final r = signatureRectUi;
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final left = r.left / uiPageSize.width * widthPts;
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final top = r.top / uiPageSize.height * heightPts;
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final w = r.width / uiPageSize.width * widthPts;
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final h = r.height / uiPageSize.height * heightPts;
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children.add(
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pw.Positioned(
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left: left,
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top: top,
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child: pw.SizedBox(
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width: w,
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height: h,
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child: pw.FittedBox(
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fit: pw.BoxFit.contain,
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child: pw.Image(sigImgObj),
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),
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),
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),
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);
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}
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return pw.Stack(children: children);
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},
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),
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);
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}
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try {
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return await out.save();
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} catch (_) {
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return null;
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}
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}
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/// Helper: write bytes returned from [exportSignedPdfFromBytes] to a file path.
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Future<bool> saveBytesToFile({
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required Uint8List bytes,
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required String outputPath,
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}) async {
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try {
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final file = File(outputPath);
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await file.writeAsBytes(bytes, flush: true);
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return true;
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} catch (_) {
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return false;
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}
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}
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}
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