Barcode Reader (Scala)

This project is a Scala application designed to read, process, and decode EAN-13 barcodes from PPM images. It performs a pipeline of image processing steps to convert color images into bit patterns and then decodes the numeric value of the barcode.

Features

• PPM Image Parsing: Reads standard .ppm (P6) color images.
• Image Processing Pipeline:
  • Grayscale Conversion: Converts RGB pixels to grayscale values (PGM format).
  • Binarization: Converts grayscale images to black and white (PBM format) using adaptive thresholding.
• Barcode Decoding:
  • Identifies start/end guard patterns.
  • Decodes digits based on parities (Odd/Even) and run-length encoding.
  • Verifies checks to ensure valid EAN-13 codes.

Project Structure

• src/main/scala/Convertor.scala: Handles image conversions (RGB -> Greyscale -> B&W).
• src/main/scala/Decoder.scala: Logic for decoding barcode bit patterns into digits.
• src/main/scala/Main.scala: Main processing flow that reads files and applies the pipeline.
• src/main/scala/MyBarcodes.scala: Entry point for user-defined input/output directories.
• src/main/scala/Parser.scala: Parses binary PPM file headers and content.
• src/main/scala/Types.scala: Definitions for internal data structures (Bit, Pixel, Image types).

Requirements

• Scala: 3.3.5
• sbt: (Simple Build Tool) 1.x or higher

Setup and Usage

1. Clone the repository:

   git clone <repository-url>
   cd <project-folder>

2. Prepare Input:

   • Create a folder named MyBarcodesInput in the project root.
   • Place your .ppm images containing barcodes into this folder.

3. Run the Application: You can run the application using sbt.

   sbt run

   When prompted, select MyBarcodes as the main class to run.

   Alternatively, you can modify MyBarcodes.scala to change the input/output directory names:

   val barcodes = readBarcodes("MyBarcodesInput", "MyBarcodesOutput")

4. Check Output:

   • The application will print the decoded barcode numbers to the console.
   • Processed black-and-white images (.pbm) will be saved in the ProcessedBarcodes (or specified output) directory.

How it Works

1. Input: A raw .ppm image.
2. Convert to Greyscale: Calculates luminance for each pixel.
3. Convert to Black & White: Uses a quadrant-based adaptive threshold to distinguish black bars from white spaces.
4. Scan & Decode:
   • Scans the middle of the image.
   • Converts pixel runs into bits (run-length matching).
   • Matches bit patterns to EAN-13 digit encodings considering parity (Left/Right/G-parity).
   • Validates the checksum digit.