feat: Receipt OCR Pipeline #69

New Issue

egullickson · 2026-02-01T18:47:42Z

egullickson commented

2026-02-01 18:47:42 +00:00

Overview

Implement receipt-specific OCR extraction in the OCR service, extracting fuel purchase data: date, total amount, gallons, price per unit, and station name.

Parent Issue: #12 (OCR-powered smart capture)
Priority: P2 - Fuel Receipt OCR
Dependencies: OCR Service Container Setup, Core OCR API Integration

Scope

Receipt Extraction Endpoint

POST /extract/receipt
Content-Type: multipart/form-data

Request:
  - file: image (HEIC, JPEG, PNG)
  - receipt_type: "fuel" (optional, for specialized extraction)

Response:
{
  "success": true,
  "receiptType": "fuel",
  "extractedFields": {
    "merchantName": { "value": "Shell", "confidence": 0.92 },
    "transactionDate": { "value": "2024-01-15", "confidence": 0.88 },
    "totalAmount": { "value": 45.67, "confidence": 0.95 },
    "fuelQuantity": { "value": 12.5, "confidence": 0.90 },
    "pricePerUnit": { "value": 3.65, "confidence": 0.87 },
    "fuelGrade": { "value": "87", "confidence": 0.75 }
  },
  "rawText": "SHELL\\n123 MAIN ST\\n...",
  "processingTimeMs": 1450
}

Image Preprocessing Pipeline

Input Image
    ↓
HEIC Conversion (pillow-heif) if needed
    ↓
Grayscale conversion
    ↓
Perspective correction (if needed)
    ↓
High contrast enhancement
    ↓
Adaptive thresholding (receipt-optimized)
    ↓
OCR with Tesseract
    ↓
Field extraction with regex + NLP

Field Extraction Patterns

Date Patterns:

DATE_PATTERNS = [
    r'\d{1,2}/\d{1,2}/\d{2,4}',      # 01/15/2024
    r'\d{1,2}-\d{1,2}-\d{2,4}',      # 01-15-2024
    r'[A-Za-z]{3}\s+\d{1,2},?\s+\d{4}',  # Jan 15, 2024
]

Amount Patterns:

TOTAL_PATTERNS = [
    r'TOTAL[:\s]*\$?([\d,]+\.\d{2})',
    r'AMOUNT[:\s]*\$?([\d,]+\.\d{2})',
    r'SALE[:\s]*\$?([\d,]+\.\d{2})',
]

GALLONS_PATTERNS = [
    r'([\d.]+)\s*(?:GAL|GALLONS?)',
    r'GALLONS?[:\s]*([\d.]+)',
]

PRICE_PATTERNS = [
    r'\$?([\d.]+)/GAL',
    r'PRICE[:\s]*\$?([\d.]+)',
]

Fuel Grade Patterns:

GRADE_PATTERNS = [
    r'(?:REGULAR|REG)\s*(\d{2})',     # REGULAR 87
    r'(?:PLUS|MID)\s*(\d{2})',        # PLUS 89
    r'(?:PREMIUM|PREM|SUPER)\s*(\d{2})',  # PREMIUM 93
    r'UNLEADED\s*(\d{2})',
    r'DIESEL',
]

Merchant Detection

Common gas station names: Shell, Chevron, Exxon, Mobil, BP, etc.
Address parsing for station location
Logo detection (optional future enhancement)

Directory Structure

ocr/app/
├── extractors/
│   ├── receipt_extractor.py   # Receipt-specific logic
│   └── fuel_receipt.py        # Fuel receipt specialization
├── preprocessors/
│   └── receipt_preprocessor.py  # Receipt-optimized preprocessing
└── patterns/
    ├── __init__.py
    ├── date_patterns.py
    ├── currency_patterns.py
    └── fuel_patterns.py

Test Cases

Input	Expected Output
Clear gas station receipt	All fields extracted, confidence > 85%
Faded thermal receipt	Most fields extracted, lower confidence
Crumpled receipt	Best effort, some fields may fail
Non-fuel receipt	receiptType: "unknown", generic extraction
Foreign receipt	Date/amount extraction, localized formats

Acceptance Criteria

Endpoint accepts HEIC, JPEG, PNG images
HEIC conversion works correctly
Preprocessing optimized for thermal receipts
Date extraction with multiple format support
Total amount extraction accurate
Gallons/liters quantity extraction
Price per unit extraction
Fuel grade detection
Merchant name extraction
Confidence scoring for each field
Processing time < 3 seconds
Unit tests for pattern matching
Integration tests with sample receipts

Technical Notes

Thermal receipts often have low contrast - preprocessing critical
Amount values may need currency symbol handling
Consider imperial/metric unit detection
Some receipts have multiple transactions - extract latest/largest
Log extraction attempts for pattern improvement

Out of Scope

Camera capture UI (see #12c)
FuelLogForm integration (see #12g)
Maintenance receipt extraction (Phase 2)

## Overview Implement receipt-specific OCR extraction in the OCR service, extracting fuel purchase data: date, total amount, gallons, price per unit, and station name. **Parent Issue**: #12 (OCR-powered smart capture) **Priority**: P2 - Fuel Receipt OCR **Dependencies**: OCR Service Container Setup, Core OCR API Integration ## Scope ### Receipt Extraction Endpoint ``` POST /extract/receipt Content-Type: multipart/form-data Request: - file: image (HEIC, JPEG, PNG) - receipt_type: "fuel" (optional, for specialized extraction) Response: { "success": true, "receiptType": "fuel", "extractedFields": { "merchantName": { "value": "Shell", "confidence": 0.92 }, "transactionDate": { "value": "2024-01-15", "confidence": 0.88 }, "totalAmount": { "value": 45.67, "confidence": 0.95 }, "fuelQuantity": { "value": 12.5, "confidence": 0.90 }, "pricePerUnit": { "value": 3.65, "confidence": 0.87 }, "fuelGrade": { "value": "87", "confidence": 0.75 } }, "rawText": "SHELL\\n123 MAIN ST\\n...", "processingTimeMs": 1450 } ``` ### Image Preprocessing Pipeline ``` Input Image ↓ HEIC Conversion (pillow-heif) if needed ↓ Grayscale conversion ↓ Perspective correction (if needed) ↓ High contrast enhancement ↓ Adaptive thresholding (receipt-optimized) ↓ OCR with Tesseract ↓ Field extraction with regex + NLP ``` ### Field Extraction Patterns **Date Patterns:** ```python DATE_PATTERNS = [ r'\d{1,2}/\d{1,2}/\d{2,4}', # 01/15/2024 r'\d{1,2}-\d{1,2}-\d{2,4}', # 01-15-2024 r'[A-Za-z]{3}\s+\d{1,2},?\s+\d{4}', # Jan 15, 2024 ] ``` **Amount Patterns:** ```python TOTAL_PATTERNS = [ r'TOTAL[:\s]*\$?([\d,]+\.\d{2})', r'AMOUNT[:\s]*\$?([\d,]+\.\d{2})', r'SALE[:\s]*\$?([\d,]+\.\d{2})', ] GALLONS_PATTERNS = [ r'([\d.]+)\s*(?:GAL|GALLONS?)', r'GALLONS?[:\s]*([\d.]+)', ] PRICE_PATTERNS = [ r'\$?([\d.]+)/GAL', r'PRICE[:\s]*\$?([\d.]+)', ] ``` **Fuel Grade Patterns:** ```python GRADE_PATTERNS = [ r'(?:REGULAR|REG)\s*(\d{2})', # REGULAR 87 r'(?:PLUS|MID)\s*(\d{2})', # PLUS 89 r'(?:PREMIUM|PREM|SUPER)\s*(\d{2})', # PREMIUM 93 r'UNLEADED\s*(\d{2})', r'DIESEL', ] ``` ### Merchant Detection - Common gas station names: Shell, Chevron, Exxon, Mobil, BP, etc. - Address parsing for station location - Logo detection (optional future enhancement) ## Directory Structure ``` ocr/app/ ├── extractors/ │ ├── receipt_extractor.py # Receipt-specific logic │ └── fuel_receipt.py # Fuel receipt specialization ├── preprocessors/ │ └── receipt_preprocessor.py # Receipt-optimized preprocessing └── patterns/ ├── __init__.py ├── date_patterns.py ├── currency_patterns.py └── fuel_patterns.py ``` ## Test Cases | Input | Expected Output | |-------|-----------------| | Clear gas station receipt | All fields extracted, confidence > 85% | | Faded thermal receipt | Most fields extracted, lower confidence | | Crumpled receipt | Best effort, some fields may fail | | Non-fuel receipt | receiptType: "unknown", generic extraction | | Foreign receipt | Date/amount extraction, localized formats | ## Acceptance Criteria - [ ] Endpoint accepts HEIC, JPEG, PNG images - [ ] HEIC conversion works correctly - [ ] Preprocessing optimized for thermal receipts - [ ] Date extraction with multiple format support - [ ] Total amount extraction accurate - [ ] Gallons/liters quantity extraction - [ ] Price per unit extraction - [ ] Fuel grade detection - [ ] Merchant name extraction - [ ] Confidence scoring for each field - [ ] Processing time < 3 seconds - [ ] Unit tests for pattern matching - [ ] Integration tests with sample receipts ## Technical Notes - Thermal receipts often have low contrast - preprocessing critical - Amount values may need currency symbol handling - Consider imperial/metric unit detection - Some receipts have multiple transactions - extract latest/largest - Log extraction attempts for pattern improvement ## Out of Scope - Camera capture UI (see #12c) - FuelLogForm integration (see #12g) - Maintenance receipt extraction (Phase 2)

egullickson added the

labels 2026-02-01 18:48:38 +00:00

egullickson referenced this issue

2026-02-01 18:49:00 +00:00

feat: OCR-powered smart capture for VIN, receipts, and owner's manuals #12

egullickson added

status

in-progress