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pdf_signature
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fix: exported document doesn't scale, rotate signature correctly

This commit is contained in:
insleker 2025-09-19 16:53:49 +08:00
parent 5a03793b54
commit 8daf5ea3ca
4 changed files with 231 additions and 198 deletions
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304
lib/data/services/export_service.dart
View File

@ -7,6 +7,8 @@ import 'package:pdf/pdf.dart' as pdf;
import 'package:printing/printing.dart' as printing;
import 'package:image/image.dart' as img;
import '../../domain/models/model.dart';
// math moved to utils in rot
import '../../utils/rotation_utils.dart' as rot;
// NOTE:
// - This exporter uses a raster snapshot of the UI (RepaintBoundary) and embeds it into a new PDF.
@ -15,50 +17,6 @@ import '../../domain/models/model.dart';
// cannot import/modify existing PDF pages. If/when a suitable FOSS library exists, wire it here.
class ExportService {
/// Compose a new PDF by rasterizing the original PDF pages (via pdfrx engine)
/// and optionally stamping a signature image on the specified page.
///
/// Inputs:
/// - [inputPath]: Path to the original PDF to read
/// - [outputPath]: Path to write the composed PDF
/// - [uiPageSize]: The logical page size used by the UI layout (SignatureCardStateNotifier.pageSize)
/// - [signatureImageBytes]: PNG/JPEG bytes of the signature image to overlay
/// - [targetDpi]: Rasterization DPI for background pages
Future<bool> exportSignedPdfFromFile({
required String inputPath,
required String outputPath,
required Size uiPageSize,
required Uint8List? signatureImageBytes,
Map<int, List<SignaturePlacement>>? placementsByPage,
Map<String, Uint8List>? libraryBytes,
double targetDpi = 144.0,
}) async {
// Read source bytes and delegate to bytes-based exporter
Uint8List? srcBytes;
try {
srcBytes = await File(inputPath).readAsBytes();
} catch (_) {
srcBytes = null;
}
if (srcBytes == null) return false;
final bytes = await exportSignedPdfFromBytes(
srcBytes: srcBytes,
uiPageSize: uiPageSize,
signatureImageBytes: signatureImageBytes,
placementsByPage: placementsByPage,
libraryBytes: libraryBytes,
targetDpi: targetDpi,
);
if (bytes == null) return false;
try {
final file = File(outputPath);
await file.writeAsBytes(bytes, flush: true);
return true;
} catch (_) {
return false;
}
}
/// Compose a new PDF from source PDF bytes; returns the resulting PDF bytes.
Future<Uint8List?> exportSignedPdfFromBytes({
required Uint8List srcBytes,
@ -68,6 +26,131 @@ class ExportService {
Map<String, Uint8List>? libraryBytes,
double targetDpi = 144.0,
}) async {
// Per-call caches to avoid redundant decode/encode and image embedding work
final Map<String, Uint8List> _processedBytesCache = <String, Uint8List>{};
final Map<String, pw.MemoryImage> _memoryImageCache =
<String, pw.MemoryImage>{};
final Map<String, double> _aspectRatioCache = <String, double>{};
// Returns a stable-ish cache key for bytes within this process (not content-hash, but good enough per-call)
String _baseKeyForBytes(Uint8List b) =>
'${identityHashCode(b)}:${b.length}';
// Fast PNG signature check (no string allocation)
bool _isPng(Uint8List bytes) {
if (bytes.length < 8) return false;
return bytes[0] == 0x89 &&
bytes[1] == 0x50 && // P
bytes[2] == 0x4E && // N
bytes[3] == 0x47 && // G
bytes[4] == 0x0D &&
bytes[5] == 0x0A &&
bytes[6] == 0x1A &&
bytes[7] == 0x0A;
}
// Resolve base (unprocessed) bytes for a placement, considering library override.
Uint8List _getBaseBytes(SignaturePlacement placement) {
Uint8List baseBytes = placement.asset.bytes;
final libKey = placement.asset.name;
if (libKey != null && libraryBytes != null) {
final libBytes = libraryBytes[libKey];
if (libBytes != null && libBytes.isNotEmpty) {
baseBytes = libBytes;
}
}
return baseBytes;
}
// Get processed bytes for a placement, with caching.
Uint8List _getProcessedBytes(SignaturePlacement placement) {
final Uint8List baseBytes = _getBaseBytes(placement);
final adj = placement.graphicAdjust;
final cacheKey =
'${_baseKeyForBytes(baseBytes)}|c=${adj.contrast}|b=${adj.brightness}|bg=${adj.bgRemoval}';
final cached = _processedBytesCache[cacheKey];
if (cached != null) return cached;
// If no graphic changes requested, return bytes as-is (conversion to PNG is deferred to MemoryImage step)
final bool needsAdjust =
(adj.contrast != 1.0 || adj.brightness != 1.0 || adj.bgRemoval);
if (!needsAdjust) {
_processedBytesCache[cacheKey] = baseBytes;
return baseBytes;
}
try {
final decoded = img.decodeImage(baseBytes);
if (decoded == null) {
_processedBytesCache[cacheKey] = baseBytes;
return baseBytes;
}
img.Image processed = decoded;
if (adj.contrast != 1.0 || adj.brightness != 1.0) {
processed = img.adjustColor(
processed,
contrast: adj.contrast,
brightness: adj.brightness,
);
}
if (adj.bgRemoval) {
processed = _removeBackground(processed);
}
final outBytes = Uint8List.fromList(img.encodePng(processed));
_processedBytesCache[cacheKey] = outBytes;
return outBytes;
} catch (_) {
// If processing fails, fall back to original
_processedBytesCache[cacheKey] = baseBytes;
return baseBytes;
}
}
// Wrap bytes in a pw.MemoryImage with caching, converting to PNG only when necessary.
pw.MemoryImage? _getMemoryImage(Uint8List bytes) {
final key = _baseKeyForBytes(bytes);
final cached = _memoryImageCache[key];
if (cached != null) return cached;
try {
if (_isPng(bytes)) {
final imgObj = pw.MemoryImage(bytes);
_memoryImageCache[key] = imgObj;
return imgObj;
}
// Convert to PNG to preserve transparency if not already PNG
final decoded = img.decodeImage(bytes);
if (decoded == null) return null;
final png = Uint8List.fromList(img.encodePng(decoded, level: 6));
final imgObj = pw.MemoryImage(png);
_memoryImageCache[key] = imgObj;
return imgObj;
} catch (_) {
return null;
}
}
// Compute and cache aspect ratio (width/height) for given bytes
double? _getAspectRatioFromBytes(Uint8List bytes) {
final key = _baseKeyForBytes(bytes);
final c = _aspectRatioCache[key];
if (c != null) return c;
try {
final decoded = img.decodeImage(bytes);
if (decoded == null || decoded.width <= 0 || decoded.height <= 0) {
return null;
}
final ar = decoded.width / decoded.height;
_aspectRatioCache[key] = ar;
return ar;
} catch (_) {
return null;
}
}
final out = pw.Document(version: pdf.PdfVersion.pdf_1_4, compress: false);
int pageIndex = 0;
bool anyPage = false;
@ -123,51 +206,22 @@ class ExportService {
final w = r.width * widthPts;
final h = r.height * heightPts;
// Process the signature asset with its graphic adjustments
Uint8List bytes = placement.asset.bytes;
if (bytes.isNotEmpty) {
try {
// Decode the image
final decoded = img.decodeImage(bytes);
if (decoded != null) {
img.Image processed = decoded;
// Apply contrast and brightness first
if (placement.graphicAdjust.contrast != 1.0 ||
placement.graphicAdjust.brightness != 0.0) {
processed = img.adjustColor(
processed,
contrast: placement.graphicAdjust.contrast,
brightness: placement.graphicAdjust.brightness,
);
}
// Apply background removal after color adjustments
if (placement.graphicAdjust.bgRemoval) {
processed = _removeBackground(processed);
}
// Encode back to PNG to preserve transparency
bytes = Uint8List.fromList(img.encodePng(processed));
}
} catch (e) {
// If processing fails, use original bytes
}
}
// Use fallback if no bytes available
// Get processed bytes (cached) and then embed as MemoryImage (cached)
Uint8List bytes = _getProcessedBytes(placement);
if (bytes.isEmpty && signatureImageBytes != null) {
bytes = signatureImageBytes;
}
if (bytes.isNotEmpty) {
pw.MemoryImage? imgObj;
try {
imgObj = pw.MemoryImage(bytes);
} catch (_) {
imgObj = null;
}
final imgObj = _getMemoryImage(bytes);
if (imgObj != null) {
// Align with RotatedSignatureImage: counterclockwise positive
final angle = rot.radians(placement.rotationDeg);
// Prefer AR from base bytes to avoid extra decode of processed
final baseBytes = _getBaseBytes(placement);
final ar = _getAspectRatioFromBytes(baseBytes);
final scaleToFit = rot.scaleToFitForAngle(angle, ar: ar);
children.add(
pw.Positioned(
left: left,
@ -177,12 +231,12 @@ class ExportService {
height: h,
child: pw.FittedBox(
fit: pw.BoxFit.contain,
child: pw.Transform.rotate(
angle:
placement.rotationDeg *
3.1415926535 /
180.0,
child: pw.Image(imgObj),
child: pw.Transform.scale(
scale: scaleToFit,
child: pw.Transform.rotate(
angle: angle,
child: pw.Image(imgObj),
),
),
),
),
@ -227,7 +281,7 @@ class ExportService {
color: pdf.PdfColors.white,
),
];
// Multi-placement stamping on fallback page
if (hasMulti && pagePlacements.isNotEmpty) {
for (var i = 0; i < pagePlacements.length; i++) {
final placement = pagePlacements[i];
@ -238,65 +292,19 @@ class ExportService {
final w = r.width * widthPts;
final h = r.height * heightPts;
// Process the signature asset with its graphic adjustments
Uint8List bytes = placement.asset.bytes;
if (bytes.isNotEmpty) {
try {
// Decode the image
final decoded = img.decodeImage(bytes);
if (decoded != null) {
img.Image processed = decoded;
// Apply contrast and brightness first
if (placement.graphicAdjust.contrast != 1.0 ||
placement.graphicAdjust.brightness != 0.0) {
processed = img.adjustColor(
processed,
contrast: placement.graphicAdjust.contrast,
brightness: placement.graphicAdjust.brightness,
);
}
// Apply background removal after color adjustments
if (placement.graphicAdjust.bgRemoval) {
processed = _removeBackground(processed);
}
// Encode back to PNG to preserve transparency
bytes = Uint8List.fromList(img.encodePng(processed));
}
} catch (e) {
// If processing fails, use original bytes
}
}
// Use fallback if no bytes available
Uint8List bytes = _getProcessedBytes(placement);
if (bytes.isEmpty && signatureImageBytes != null) {
bytes = signatureImageBytes;
}
if (bytes.isNotEmpty) {
pw.MemoryImage? imgObj;
try {
// Ensure PNG for transparency if not already
final asStr = String.fromCharCodes(bytes.take(8));
final isPng =
bytes.length > 8 &&
bytes[0] == 0x89 &&
asStr.startsWith('\u0089PNG');
if (isPng) {
imgObj = pw.MemoryImage(bytes);
} else {
final decoded = img.decodeImage(bytes);
if (decoded != null) {
final png = img.encodePng(decoded, level: 6);
imgObj = pw.MemoryImage(Uint8List.fromList(png));
}
}
} catch (_) {
imgObj = null;
}
final imgObj = _getMemoryImage(bytes);
if (imgObj != null) {
final angle = rot.radians(placement.rotationDeg);
final baseBytes = _getBaseBytes(placement);
final ar = _getAspectRatioFromBytes(baseBytes);
final scaleToFit = rot.scaleToFitForAngle(angle, ar: ar);
children.add(
pw.Positioned(
left: left,
@ -306,10 +314,12 @@ class ExportService {
height: h,
child: pw.FittedBox(
fit: pw.BoxFit.contain,
child: pw.Transform.rotate(
angle:
placement.rotationDeg * 3.1415926535 / 180.0,
child: pw.Image(imgObj),
child: pw.Transform.scale(
scale: scaleToFit,
child: pw.Transform.rotate(
angle: angle,
child: pw.Image(imgObj),
),
),
),
),

60
lib/ui/features/signature/widgets/image_editor_dialog.dart
View File

@ -41,7 +41,7 @@ class _ImageEditorDialogState extends State<ImageEditorDialog> {
late bool _bgRemoval;
late double _contrast;
late double _brightness;
late double _rotation;
late final ValueNotifier<double> _rotation;
// Cached image data
late Uint8List _originalBytes; // Original asset bytes (never mutated)
@ -59,7 +59,7 @@ class _ImageEditorDialogState extends State<ImageEditorDialog> {
_bgRemoval = widget.initialGraphicAdjust.bgRemoval;
_contrast = widget.initialGraphicAdjust.contrast;
_brightness = widget.initialGraphicAdjust.brightness;
_rotation = widget.initialRotation;
_rotation = ValueNotifier<double>(widget.initialRotation);
_originalBytes = widget.asset.bytes;
// Decode lazily only if/when background removal is needed
if (_bgRemoval) {
@ -172,6 +172,7 @@ class _ImageEditorDialogState extends State<ImageEditorDialog> {
@override
void dispose() {
_rotation.dispose();
_bgRemovalDebounce?.cancel();
super.dispose();
}
@ -206,19 +207,20 @@ class _ImageEditorDialogState extends State<ImageEditorDialog> {
),
child: ClipRRect(
borderRadius: BorderRadius.circular(8),
child:
_bgRemoval
? RotatedSignatureImage(
bytes: _displayBytes,
rotationDeg: _rotation,
)
: ColorFiltered(
colorFilter: _currentColorFilter(),
child: RotatedSignatureImage(
bytes: _displayBytes,
rotationDeg: _rotation,
),
),
child: ValueListenableBuilder<double>(
valueListenable: _rotation,
builder: (context, rot, child) {
final image = RotatedSignatureImage(
bytes: _displayBytes,
rotationDeg: rot,
);
if (_bgRemoval) return image;
return ColorFiltered(
colorFilter: _currentColorFilter(),
child: image,
);
},
),
),
),
),
@ -248,16 +250,26 @@ class _ImageEditorDialogState extends State<ImageEditorDialog> {
children: [
Text(l10n.rotate),
Expanded(
child: Slider(
key: const Key('sld_rotation'),
min: -180,
max: 180,
divisions: 72,
value: _rotation,
onChanged: (v) => setState(() => _rotation = v),
child: ValueListenableBuilder<double>(
valueListenable: _rotation,
builder: (context, rot, _) {
return Slider(
key: const Key('sld_rotation'),
min: -180,
max: 180,
divisions: 72,
value: rot,
onChanged: (v) => _rotation.value = v,
);
},
),
),
Text('${_rotation.toStringAsFixed(0)}°'),
ValueListenableBuilder<double>(
valueListenable: _rotation,
builder:
(context, rot, _) =>
Text('${rot.toStringAsFixed(0)}°'),
),
],
),
const SizedBox(height: 12),
@ -269,7 +281,7 @@ class _ImageEditorDialogState extends State<ImageEditorDialog> {
onPressed:
() => Navigator.of(context).pop(
ImageEditorResult(
rotation: _rotation,
rotation: _rotation.value,
graphicAdjust: domain.GraphicAdjust(
contrast: _contrast,
brightness: _brightness,

44
lib/ui/features/signature/widgets/rotated_signature_image.dart
View File

@ -1,7 +1,7 @@
import 'dart:math' as math;
import 'dart:typed_data';
import 'package:flutter/material.dart';
import 'package:image/image.dart' as img;
import '../../../../utils/rotation_utils.dart' as rot;
/// A lightweight widget to render signature bytes with rotation and an
/// angle-aware scale-to-fit so the rotated image stays within its bounds.
@ -9,7 +9,7 @@ class RotatedSignatureImage extends StatefulWidget {
const RotatedSignatureImage({
super.key,
required this.bytes,
this.rotationDeg = 0.0,
this.rotationDeg = 0.0, // counterclockwise as positive
this.filterQuality = FilterQuality.low,
this.semanticLabel,
});
@ -45,8 +45,9 @@ class _RotatedSignatureImageState extends State<RotatedSignatureImage> {
@override
void didUpdateWidget(covariant RotatedSignatureImage oldWidget) {
super.didUpdateWidget(oldWidget);
if (!identical(oldWidget.bytes, widget.bytes) ||
oldWidget.rotationDeg != widget.rotationDeg) {
// Only re-resolve when the bytes change. Rotation does not affect
// intrinsic aspect ratio, so avoid expensive decode/resolve on slider drags.
if (!identical(oldWidget.bytes, widget.bytes)) {
_derivedAspectRatio = null;
_resolveImage();
}
@ -60,24 +61,21 @@ class _RotatedSignatureImageState extends State<RotatedSignatureImage> {
void _resolveImage() {
_unlisten();
// Decode synchronously to get aspect ratio
// Guard against empty / invalid bytes that some simplified tests may inject.
// Resolve via ImageProvider; when first frame arrives, capture intrinsic size.
// Avoid synchronous decode on UI thread to keep rotation smooth.
if (widget.bytes.isEmpty) {
_setAspectRatio(1.0); // assume square to avoid layout exceptions
_setAspectRatio(1.0); // safe fallback
return;
}
// One-time synchronous header decode to establish aspect ratio quickly.
// This only runs when bytes change (not on rotation), so it's acceptable.
try {
final decoded = img.decodePng(widget.bytes);
if (decoded != null) {
final w = decoded.width;
final h = decoded.height;
if (w > 0 && h > 0) {
_setAspectRatio(w / h);
}
final decoded = img.decodeImage(widget.bytes);
if (decoded != null && decoded.width > 0 && decoded.height > 0) {
_setAspectRatio(decoded.width / decoded.height);
}
} catch (_) {
// Swallow decode errors for test-provided dummy data; assume square.
_setAspectRatio(1.0);
// ignore decode errors and rely on image stream listener
}
final stream = _provider.resolve(createLocalImageConfiguration(context));
_stream = stream;
@ -107,7 +105,7 @@ class _RotatedSignatureImageState extends State<RotatedSignatureImage> {
@override
Widget build(BuildContext context) {
final angle = widget.rotationDeg * math.pi / 180.0;
final angle = rot.ccwRadians(widget.rotationDeg);
Widget img = Image.memory(
widget.bytes,
fit: widget.fit,
@ -115,6 +113,7 @@ class _RotatedSignatureImageState extends State<RotatedSignatureImage> {
filterQuality: widget.filterQuality,
alignment: widget.alignment,
semanticLabel: widget.semanticLabel,
isAntiAlias: false,
errorBuilder: (context, error, stackTrace) {
// Return a placeholder for invalid images
return Container(
@ -125,16 +124,7 @@ class _RotatedSignatureImageState extends State<RotatedSignatureImage> {
);
if (angle != 0.0) {
final double c = math.cos(angle).abs();
final double s = math.sin(angle).abs();
final ar = _derivedAspectRatio;
double scaleToFit;
if (ar != null && ar > 0) {
scaleToFit = math.min(ar / (ar * c + s), 1.0 / (ar * s + c));
} else {
// Fallback: square approximation
scaleToFit = 1.0 / (c + s).clamp(1.0, double.infinity);
}
final scaleToFit = rot.scaleToFitForAngle(angle, ar: _derivedAspectRatio);
img = Transform.scale(
scale: scaleToFit,
child: Transform.rotate(angle: angle, child: img),

21
lib/utils/rotation_utils.dart Normal file
View File

@ -0,0 +1,21 @@
import 'dart:math' as math;
/// Convert degrees to radians with counterclockwise as positive in screen space
/// by inverting the sign (because screen Y axis points downwards).
double ccwRadians(double degrees) => -degrees * math.pi / 180.0;
/// Classic math convention: positive degrees rotate counterclockwise.
/// No screen-space Y-inversion applied.
double radians(double degrees) => degrees * math.pi / 180.0;
/// Compute scale factor to keep a rotated rectangle of aspect ratio [ar]
/// within a unit 1x1 box. If [ar] is null or <= 0, fall back to a square.
/// Returns the scale to apply before rotation.
double scaleToFitForAngle(double angleRad, {double? ar}) {
final double c = angleRad == 0.0 ? 1.0 : math.cos(angleRad).abs();
final double s = angleRad == 0.0 ? 0.0 : math.sin(angleRad).abs();
if (ar != null && ar > 0) {
return math.min(ar / (ar * c + s), 1.0 / (ar * s + c));
}
return 1.0 / (c + s).clamp(1.0, double.infinity);
}