filter at pdf generation

App.tsx

@@ -29,8 +29,8 @@ export default function App() {
   }, []);
 
   const handleSaveDocument = useCallback(
-    (pages: ScannedPage[], _filter: FilterMode) => {
-      const doc = createDocument(pages);
+    (pages: ScannedPage[], filter: FilterMode) => {
+      const doc = createDocument(pages, filter);
       setPendingPages([]);
       setViewingDoc(doc);
       setScreen('viewer');

android/app/src/main/java/com/lensapp/PdfGeneratorModule.kt

@@ -1,6 +1,11 @@
 package com.lensapp
 
+import android.graphics.Bitmap
 import android.graphics.BitmapFactory
+import android.graphics.Canvas
+import android.graphics.ColorMatrix
+import android.graphics.ColorMatrixColorFilter
+import android.graphics.Paint
 import android.graphics.RectF
 import android.graphics.pdf.PdfDocument
 import com.facebook.react.bridge.Promise
@@ -16,17 +21,26 @@ class PdfGeneratorModule(private val reactContext: ReactApplicationContext) :
 
     override fun getName() = "PdfGenerator"
 
+    private fun applyFilter(src: Bitmap, matrixValues: ReadableArray): Bitmap {
+        val floats = FloatArray(20) { matrixValues.getDouble(it).toFloat() }
+        val out = Bitmap.createBitmap(src.width, src.height, Bitmap.Config.ARGB_8888)
+        Canvas(out).drawBitmap(src, 0f, 0f, Paint().apply { colorFilter = ColorMatrixColorFilter(ColorMatrix(floats)) })
+        return out
+    }
+
     @ReactMethod
-    fun generate(imagePaths: ReadableArray, fileName: String, promise: Promise) {
+    fun generate(imagePaths: ReadableArray, fileName: String, matrix: ReadableArray, promise: Promise) {
         try {
             val outDir = File(reactContext.filesDir, "pdfs").also { it.mkdirs() }
             val outFile = File(outDir, "$fileName.pdf")
             val doc = PdfDocument()
 
             for (i in 0 until imagePaths.size()) {
                 val path = imagePaths.getString(i)!!.removePrefix("file://")
-                val bitmap = BitmapFactory.decodeFile(path)
+                val raw = BitmapFactory.decodeFile(path)
                     ?: throw Exception("Failed to decode image: $path")
+                val bitmap = applyFilter(raw, matrix)
+                if (raw !== bitmap) raw.recycle()
 
                 // A4 at 72 DPI: 595 x 842 points
                 val pageWidth = 595

ios/LensApp/PdfGenerator.m

@@ -1,12 +1,29 @@
 #import "PdfGenerator.h"
 #import <UIKit/UIKit.h>
+#import <CoreImage/CoreImage.h>
 
 @implementation PdfGenerator
 
 RCT_EXPORT_MODULE();
 
+- (UIImage *)applyMatrix:(UIImage *)image matrix:(NSArray *)m {
+    CIImage *ci = [CIImage imageWithCGImage:image.CGImage];
+    CIFilter *f = [CIFilter filterWithName:@"CIColorMatrix"];
+    [f setValue:ci forKey:kCIInputImageKey];
+    [f setValue:[CIVector vectorWithX:[m[0] floatValue] Y:[m[1] floatValue] Z:[m[2] floatValue] W:[m[3] floatValue]] forKey:@"inputRVector"];
+    [f setValue:[CIVector vectorWithX:[m[5] floatValue] Y:[m[6] floatValue] Z:[m[7] floatValue] W:[m[8] floatValue]] forKey:@"inputGVector"];
+    [f setValue:[CIVector vectorWithX:[m[10] floatValue] Y:[m[11] floatValue] Z:[m[12] floatValue] W:[m[13] floatValue]] forKey:@"inputBVector"];
+    [f setValue:[CIVector vectorWithX:[m[15] floatValue] Y:[m[16] floatValue] Z:[m[17] floatValue] W:[m[18] floatValue]] forKey:@"inputAVector"];
+    [f setValue:[CIVector vectorWithX:[m[4] floatValue] Y:[m[9] floatValue] Z:[m[14] floatValue] W:[m[19] floatValue]] forKey:@"inputBiasVector"];
+    CGImageRef cg = [[CIContext context] createCGImage:f.outputImage fromRect:f.outputImage.extent];
+    UIImage *result = [UIImage imageWithCGImage:cg];
+    CGImageRelease(cg);
+    return result;
+}
+
 RCT_EXPORT_METHOD(generate:(NSArray *)imagePaths
                   fileName:(NSString *)fileName
+                  matrix:(NSArray *)matrix
                   resolver:(RCTPromiseResolveBlock)resolve
                   rejecter:(RCTPromiseRejectBlock)reject)
 {
@@ -31,8 +48,9 @@ @implementation PdfGenerator
                                    withActions:^(UIGraphicsPDFRendererContext *ctx) {
             for (NSString *rawPath in imagePaths) {
                 NSString *path = [rawPath hasPrefix:@"file://"] ? [rawPath substringFromIndex:7] : rawPath;
-                UIImage *image = [UIImage imageWithContentsOfFile:path];
-                if (!image) continue;
+                UIImage *raw = [UIImage imageWithContentsOfFile:path];
+                if (!raw) continue;
+                UIImage *image = [self applyMatrix:raw matrix:matrix];
 
                 [ctx beginPage];
 

jest.config.js

@@ -6,6 +6,6 @@ module.exports = {
   ],
   moduleFileExtensions: ['ts', 'tsx', 'js', 'jsx', 'json'],
   transformIgnorePatterns: [
-    'node_modules/(?!(react-native|@react-native|react-native-document-scanner-plugin|react-native-fs|react-native-html-to-pdf|react-native-share)/)',
+    'node_modules/(?!(react-native|@react-native|react-native-document-scanner-plugin|react-native-fs|react-native-html-to-pdf|react-native-share|react-native-color-matrix-image-filters|rn-color-matrices|concat-color-matrices)/)',
   ],
 };

package.json

@@ -13,6 +13,7 @@
   "dependencies": {
     "react": "18.2.0",
     "react-native": "0.73.0",
+    "react-native-color-matrix-image-filters": "^8.0.2",
     "react-native-document-scanner-plugin": "^2.0.4",
     "react-native-fs": "^2.20.0",
     "react-native-share": "^12.2.6"

src/__tests__/generatePdf.test.ts

@@ -4,6 +4,11 @@ jest.mock('react-native', () => ({
       generate: jest.fn(),
     },
   },
+  Platform: {OS: 'android'},
+}));
+
+jest.mock('../utils/filterMatrices', () => ({
+  getFilterMatrix: jest.fn(() => new Array(20).fill(0)),
 }));
 
 import {NativeModules} from 'react-native';
@@ -30,6 +35,7 @@ describe('generatePdf', () => {
     expect(mockGenerate).toHaveBeenCalledWith(
       ['file:///mock/scans/scan1.jpg', '/mock/scans/scan2.jpg'],
       'test',
+      expect.any(Array),
     );
   });
 

src/components/DocumentCard.tsx

@@ -1,7 +1,9 @@
 import React from 'react';
 import {View, Text, Image, TouchableOpacity, StyleSheet} from 'react-native';
+import {ColorMatrix} from 'react-native-color-matrix-image-filters';
 import {ScannedDocument} from '../types';
 import {formatDate} from '../utils/imageProcessing';
+import {getFilterMatrix} from '../utils/filterMatrices';
 import {useTheme} from '../theme';
 
 interface Props {
@@ -20,7 +22,9 @@ export default function DocumentCard({document, onPress}: Props) {
       activeOpacity={0.8}>
       <View style={styles.thumbContainer}>
         {thumb ? (
-          <Image source={{uri: thumb}} style={styles.thumb} resizeMode="cover" />
+          <ColorMatrix matrix={getFilterMatrix(document.filter)} style={styles.thumb}>
+            <Image source={{uri: thumb}} style={styles.thumb} resizeMode="cover" />
+          </ColorMatrix>
         ) : (
           <View style={[styles.thumb, {backgroundColor: t.border}]} />
         )}

src/hooks/useDocumentStore.ts

@@ -1,6 +1,6 @@
 import {useState, useCallback, useEffect, useRef} from 'react';
 import RNFS from 'react-native-fs';
-import {ScannedDocument, ScannedPage} from '../types';
+import {ScannedDocument, ScannedPage, FilterMode} from '../types';
 
 let idCounter = 0;
 const uid = () => `${Date.now()}-${++idCounter}`;
@@ -42,12 +42,13 @@ export function useDocumentStore() {
     }
   }, [documents]);
 
-  const createDocument = useCallback((pages: ScannedPage[]): ScannedDocument => {
+  const createDocument = useCallback((pages: ScannedPage[], filter: FilterMode): ScannedDocument => {
     const doc: ScannedDocument = {
       id: uid(),
       pages,
       createdAt: new Date(),
       name: `Scan ${new Date().toLocaleDateString()}`,
+      filter,
     };
     setDocuments(prev => [doc, ...prev]);
     return doc;

src/screens/ReviewScreen.tsx

@@ -10,6 +10,8 @@ import {
   StatusBar,
   Alert,
 } from 'react-native';
+import {ColorMatrix} from 'react-native-color-matrix-image-filters';
+import {getFilterMatrix} from '../utils/filterMatrices';
 import {ScannedPage, FilterMode} from '../types';
 import FilterPicker from '../components/FilterPicker';
 import {useTheme} from '../theme';
@@ -28,14 +30,11 @@ export default function ReviewScreen({pages, onSave, onAddMore, onCancel}: Props
   const [filter, setFilter] = useState<FilterMode>('original');
   const [currentIndex, setCurrentIndex] = useState(0);
 
-  const imageContainerStyle = () => {
-    switch (filter) {
-      case 'grayscale': return styles.filterGrayscale;
-      case 'blackwhite': return styles.filterBW;
-      case 'enhanced': return styles.filterEnhanced;
-      default: return null;
-    }
-  };
+  const renderImage = (page: ScannedPage) => (
+    <ColorMatrix matrix={getFilterMatrix(filter)} style={styles.pageImage}>
+      <Image source={{uri: page.uri}} style={styles.pageImage} resizeMode="contain" />
+    </ColorMatrix>
+  );
 
   return (
     <View style={[styles.container, {backgroundColor: t.bg}]}>
@@ -63,8 +62,8 @@ export default function ReviewScreen({pages, onSave, onAddMore, onCancel}: Props
         }}>
         {pages.map(page => (
           <View key={page.id} style={styles.pageContainer}>
-            <View style={[styles.imageWrapper, imageContainerStyle()]}>
-              <Image source={{uri: page.uri}} style={styles.pageImage} resizeMode="contain" />
+            <View style={styles.imageWrapper}>
+              {renderImage(page)}
             </View>
           </View>
         ))}
@@ -128,9 +127,6 @@ const styles = StyleSheet.create({
   },
   imageWrapper: {flex: 1, width: '100%', borderRadius: 8, overflow: 'hidden'},
   pageImage: {flex: 1, width: '100%'},
-  filterGrayscale: {opacity: 0.9},
-  filterBW: {opacity: 1},
-  filterEnhanced: {opacity: 1},
   dots: {flexDirection: 'row', justifyContent: 'center', gap: 6, paddingVertical: 8},
   dot: {width: 6, height: 6, borderRadius: 3},
   dotActive: {backgroundColor: '#007AFF', width: 18},

src/screens/ViewerScreen.tsx

@@ -14,8 +14,10 @@ import {
   TextInput,
 } from 'react-native';
 import Share from 'react-native-share';
+import {ColorMatrix} from 'react-native-color-matrix-image-filters';
 import {ScannedDocument} from '../types';
 import {generatePdf} from '../utils/generatePdf';
+import {getFilterMatrix} from '../utils/filterMatrices';
 import {useTheme} from '../theme';
 
 const {width: SW} = Dimensions.get('window');
@@ -44,7 +46,7 @@ export default function ViewerScreen({document, onBack, onDelete, onRename}: Pro
       const label = pageIndices?.length === 1
         ? `${document.name} — page ${pageIndices[0] + 1}`
         : document.name;
-      const pdfPath = await generatePdf(pages, label);
+      const pdfPath = await generatePdf(pages, label, document.filter);
       await Share.open({
         title: label,
         type: 'application/pdf',
@@ -98,11 +100,13 @@ export default function ViewerScreen({document, onBack, onDelete, onRename}: Pro
         }}>
         {document.pages.map((page, i) => (
           <View key={page.id} style={styles.pageContainer}>
-            <Image
-              source={{uri: page.uri}}
-              style={styles.pageImage}
-              resizeMode="contain"
-            />
+            <ColorMatrix matrix={getFilterMatrix(document.filter)} style={styles.pageImage}>
+              <Image
+                source={{uri: page.uri}}
+                style={styles.pageImage}
+                resizeMode="contain"
+              />
+            </ColorMatrix>
             <Text style={[styles.pageNum, {color: t.textSecondary}]}>Page {i + 1}</Text>
           </View>
         ))}

src/types/index.ts

@@ -3,6 +3,7 @@ export interface ScannedDocument {
   pages: ScannedPage[];
   createdAt: Date;
   name: string;
+  filter: FilterMode;
 }
 
 export interface ScannedPage {

src/utils/filterMatrices.ts

@@ -0,0 +1,15 @@
+import {concatColorMatrices, saturate, contrast, brightness, normal} from 'react-native-color-matrix-image-filters';
+import {FilterMode} from '../types';
+
+export function getFilterMatrix(filter: FilterMode): number[] {
+  switch (filter) {
+    case 'grayscale':
+      return saturate(0);
+    case 'blackwhite':
+      return concatColorMatrices(saturate(0), contrast(4));
+    case 'enhanced':
+      return concatColorMatrices(contrast(1.3), brightness(1.1));
+    default:
+      return normal();
+  }
+}

src/utils/generatePdf.ts

@@ -1,10 +1,11 @@
 import {NativeModules} from 'react-native';
-import {ScannedPage} from '../types';
+import {ScannedPage, FilterMode} from '../types';
+import {getFilterMatrix} from './filterMatrices';
 
 const {PdfGenerator} = NativeModules;
 
-export async function generatePdf(pages: ScannedPage[], name: string): Promise<string> {
+export async function generatePdf(pages: ScannedPage[], name: string, filter: FilterMode = 'original'): Promise<string> {
   const imagePaths = pages.map(p => p.uri);
   const fileName = name.replace(/[^a-z0-9_\-]/gi, '_');
-  return PdfGenerator.generate(imagePaths, fileName);
+  return PdfGenerator.generate(imagePaths, fileName, getFilterMatrix(filter));
 }