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refactor: simplify barcode detection by removing canvas splitting

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Remove canvas splitting logic since zxing-wasm natively supports multiple barcode detection with maxNumberOfSymbols parameter. Reduces code by 69 lines and improves performance by requiring only a single decode call per canvas. Set maxNumberOfSymbols to 10 for realistic utility bill use case.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
This commit is contained in:
Knee Cola
2025-12-20 01:00:46 +01:00
parent 5b0497891a
commit fcc1ede4d0
1 changed files with 66 additions and 135 deletions
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201
app/lib/pdf/barcodeDecoderWasm.ts
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@@ -3,14 +3,14 @@ import { readBarcodes, prepareZXingModule, type ReaderOptions } from 'zxing-wasm
// Configure WASM file location (similar to how pdf.worker.min.mjs is configured)
prepareZXingModule({
overrides: {
locateFile: (path, prefix) => {
if (path.endsWith('.wasm')) {
return window.location.origin + '/zxing_reader.wasm';
}
return prefix + path;
overrides: {
locateFile: (path, prefix) => {
if (path.endsWith('.wasm')) {
return window.location.origin + '/zxing_reader.wasm';
}
return prefix + path;
}
}
}
});
export type BillInfo = {
@@ -31,7 +31,7 @@ export type BillInfo = {
};
/** Breaks current microtask execution and gives the UI thread a chance to do a re-paint */
const yieldToBrowser = (_label:string) => new Promise<boolean>((resolve) => {
const yieldToBrowser = (_label: string) => new Promise<boolean>((resolve) => {
setTimeout(() => {
resolve(true);
}, 0);
@@ -61,7 +61,7 @@ const yieldToBrowser = (_label:string) => new Promise<boolean>((resolve) => {
* description:Akontacijska rata za 01.2024.
*
*/
const parseHubText = (text: string):BillInfo => {
const parseHubText = (text: string): BillInfo => {
const [
header,
currency,
@@ -102,12 +102,12 @@ const parseHubText = (text: string):BillInfo => {
* @param {File} imageFile - a file containing an image
* @return {Promise<HTMLCanvasElement>} the canvas with the image rendered onto it
*/
const file2canvas = async function (imageFile:File): Promise<HTMLCanvasElement> {
const file2canvas = async function (imageFile: File): Promise<HTMLCanvasElement> {
const reader = new FileReader();
const canvas = await new Promise<HTMLCanvasElement>((resolve, reject) => {
reader.onload = (progressEvent:ProgressEvent<FileReader>) => {
reader.onload = (progressEvent: ProgressEvent<FileReader>) => {
const img = new Image();
img.onload = () => {
@@ -115,8 +115,8 @@ const file2canvas = async function (imageFile:File): Promise<HTMLCanvasElement>
const ctx = canvas.getContext('2d');
canvas.width = img.width;
canvas.height = img.height;
if(!ctx) {
if (!ctx) {
reject("Context is not set")
return;
}
@@ -127,7 +127,7 @@ const file2canvas = async function (imageFile:File): Promise<HTMLCanvasElement>
};
const result = (progressEvent.target as FileReader).result;
img.src = result as string;
};
@@ -135,7 +135,7 @@ const file2canvas = async function (imageFile:File): Promise<HTMLCanvasElement>
reader.readAsDataURL(imageFile);
});
return(canvas);
return (canvas);
}
/**
@@ -143,31 +143,31 @@ const file2canvas = async function (imageFile:File): Promise<HTMLCanvasElement>
* @param {String} imageBase64 - base64 encoded image string
* @return {Promise<HTMLCanvasElement>} the canvas with the image rendered onto it
*/
const image2canvas = async function (imageBase64:string): Promise<HTMLCanvasElement> {
const image2canvas = async function (imageBase64: string): Promise<HTMLCanvasElement> {
const canvas = await new Promise<HTMLCanvasElement>((resolve, reject) => {
const img = new Image();
const img = new Image();
img.onload = () => {
const canvas = document.createElement('canvas');
const ctx = canvas.getContext('2d');
canvas.width = img.width;
canvas.height = img.height;
if(!ctx) {
reject("Context is not set")
return;
}
img.onload = () => {
const canvas = document.createElement('canvas');
const ctx = canvas.getContext('2d');
canvas.width = img.width;
canvas.height = img.height;
ctx.drawImage(img, 0, 0);
if (!ctx) {
reject("Context is not set")
return;
}
resolve(canvas);
};
ctx.drawImage(img, 0, 0);
img.src = imageBase64;
resolve(canvas);
};
img.src = imageBase64;
});
return(canvas);
return (canvas);
};
/**
@@ -175,7 +175,7 @@ const image2canvas = async function (imageBase64:string): Promise<HTMLCanvasElem
* @param {File} pdfFile - a file containing a PDF document
* @return {Promise<HTMLCanvasElement>} the canvas with the first page of the PDF
*/
const pdf2canvas = async function (pdfFile:File): Promise<Array<HTMLCanvasElement>> {
const pdf2canvas = async function (pdfFile: File): Promise<Array<HTMLCanvasElement>> {
const reader = new FileReader();
const data = await new Promise<Uint8Array>((resolve, reject) => {
@@ -193,8 +193,8 @@ const pdf2canvas = async function (pdfFile:File): Promise<Array<HTMLCanvasElemen
const canvases: Array<HTMLCanvasElement> = [];
for(let i = 0; i< pdf.numPages; i++) {
const page: PDFPageProxy = await pdf.getPage(i+1);
for (let i = 0; i < pdf.numPages; i++) {
const page: PDFPageProxy = await pdf.getPage(i + 1);
const scale = 4;
const viewport = page.getViewport({ scale });
@@ -209,7 +209,7 @@ const pdf2canvas = async function (pdfFile:File): Promise<Array<HTMLCanvasElemen
canvases.push(canvas);
}
return(canvases);
return (canvases);
}
export type DecodeResult = {
@@ -235,107 +235,38 @@ const canvasToImageData = (canvas: HTMLCanvasElement): ImageData => {
* @param {HTMLCanvasElement} canvas - the canvas to search for PDF417 codes
* @return {Promise<Array<DecodeResult> | null>} - an array of decoded results
* */
const decodeFromCanvas = async (canvas:HTMLCanvasElement): Promise<Array<DecodeResult> | null> => {
const decodeFromCanvas = async (canvas: HTMLCanvasElement): Promise<Array<DecodeResult> | null> => {
try {
const readerOptions: ReaderOptions = {
tryHarder: true,
formats: ['PDF417'],
maxNumberOfSymbols: 255,
maxNumberOfSymbols: 10,
};
const width = canvas.width;
const height = canvas.height;
// give browser a chance to re-paint
// this is needed to avoid UI freezing when decoding large images
await yieldToBrowser('decodeFromCanvas');
// Canvas can contain multiple PDF417 codes, so we need to try to find them all
// The issue is that zxing-wasm can only decode one code at a time in some cases
// and it will throw an error if it finds more than one code.
// To solve this, we will try splitting the canvas into different number of subsections
// and decode each subsection separately. The best result will be the one with the most codes found.
const splits = [5,4,3,2,1,0];
const imageData = canvasToImageData(canvas);
const results = await readBarcodes(imageData, readerOptions);
let bestResult: Array<DecodeResult>|null = null;
const codesFound: Array<DecodeResult> = results
.filter(result => result.text)
.map((result) => ({
hub3aText: result.text,
billInfo: parseHubText(result.text),
}));
for(let splitIx = 0; splitIx < splits.length; splitIx++) {
const split = splits[splitIx];
return (codesFound);
const overlap = split === 0 ? 0 : Math.round(height / 50); // 50% overlap ensuring that we don't miss any codes that might be split between sections
const sectionHeight = split === 0 ? height : (Math.floor( Math.floor(height / split) + overlap));
const canvasSections = Array.from({ length: split+1 }, (_, i) => {
const sectionCanvas = document.createElement('canvas');
sectionCanvas.width = width;
sectionCanvas.height = sectionHeight;
const sectionContext = sectionCanvas.getContext('2d');
if (!sectionContext) {
throw new Error('Failed to get canvas context');
}
// Calculate the starting Y position for each section
const startY = i===0 ? 0 : i * (sectionHeight) - overlap;
// Draw the section of the original canvas onto the new section canvas
sectionContext.drawImage(canvas, 0, startY, width, sectionHeight, 0, 0, width, sectionHeight);
return sectionCanvas;
});
const codesFoundInSection: Array<DecodeResult> = [];
// Try to decode each section
for (const sectionCanvas of canvasSections) {
try {
// give browser a chance to re-paint
// this is needed to avoid UI freezing when decoding large images
await yieldToBrowser('decodeFromCanvas');
const imageData = canvasToImageData(sectionCanvas);
const results = await readBarcodes(imageData, readerOptions);
for (const result of results) {
const hub3aText = result.text;
if (hub3aText) {
codesFoundInSection.push({
hub3aText,
billInfo: parseHubText(hub3aText),
});
}
}
} catch (error) {
// If no code was found in the current section an error will be thrown
// -> we can ignore it
} finally {
}
}
await yieldToBrowser('after decodeFromCanvas');
// IF in this iteration we found less codes than in the previous best result,
// we can stop searching for more codes
// This is because the number of codes found in each section will only decrease
// as we increase the number of sections (split)
if(bestResult && codesFoundInSection.length <= bestResult.length) {
return(bestResult);
}
bestResult = codesFoundInSection;
};
return(bestResult);
} catch(ex:any) {
console.log(ex);
return(null);
} catch (error) {
console.log(error);
return (null);
}
}
/** Finds PDF417 code within a base64 encoded image and decodes it */
export const decodeFromImage = async (imageBase64:string): Promise<DecodeResult|null> => {
export const decodeFromImage = async (imageBase64: string): Promise<DecodeResult | null> => {
const canvas = await image2canvas(imageBase64);
const readerOptions: ReaderOptions = {
@@ -346,40 +277,40 @@ export const decodeFromImage = async (imageBase64:string): Promise<DecodeResult|
const imageData = canvasToImageData(canvas);
const results = await readBarcodes(imageData, readerOptions);
if (results.length === 0) {
return null;
}
const hub3aText = results[0].text;
return({
return ({
hub3aText,
billInfo: parseHubText(hub3aText)
});
}
/** Finds PDF417 code within a file and decodes it */
const decodeFromFile = async (file:File): Promise<DecodeResult[]|null> => {
switch(file.type) {
const decodeFromFile = async (file: File): Promise<DecodeResult[] | null> => {
switch (file.type) {
case 'image/png':
case 'image/jpeg':
return(await decodeFromCanvas( await file2canvas(file) ));
return (await decodeFromCanvas(await file2canvas(file)));
case 'application/pdf':
const pageCanvas = await pdf2canvas(file);
// go through each page of the PDF and decode the PDF417 codes
// if there are multiple pages, we will decode each page separately
// and return the results from all pages
const results = (await Promise.all(pageCanvas.map(async (canvas) => {
await yieldToBrowser('decodeFromCanvas');
return await decodeFromCanvas(canvas);
})))
await yieldToBrowser('decodeFromCanvas');
return await decodeFromCanvas(canvas);
})))
// remove null results (pages with no PDF417 codes)
.filter((result) => result !== null)
// flatten the array of arrays into a single array
.flat() as DecodeResult[];
return(results);
return (results);
default:
console.error(file.name, 'is not a .pdf file.');
return null;
@@ -391,13 +322,13 @@ const decodeFromFile = async (file:File): Promise<DecodeResult[]|null> => {
* @param {Event} event - The change event from an HTMLInputElement.
* @return {Promise<HTMLCanvasElement | null>} The canvas with the first page of the PDF, or null if the document is not a PDF.
*/
export async function findDecodePdf417(event: React.ChangeEvent<HTMLInputElement>): Promise<Array<DecodeResult>|null> {
export async function findDecodePdf417(event: React.ChangeEvent<HTMLInputElement>): Promise<Array<DecodeResult> | null> {
const file = (event.target as HTMLInputElement).files?.[0];
if(!file) {
if (!file) {
console.error('No file was selected.');
return null;
}
return(await decodeFromFile(file));
return (await decodeFromFile(file));
}