PNM Image Generator

A lightweight C program for generating Netpbm format images (PBM, PGM, and PPM) with customizable patterns, gradients, and color effects.

Overview

This tool creates three types of Netpbm format images with procedurally generated patterns:

• PBM (Portable BitMap): Black and white images with geometric patterns
• PGM (Portable GrayMap): Grayscale images with smooth gradient effects
• PPM (Portable PixMap): Full-color images with multi-channel color gradients

Perfect for testing image processing pipelines, generating test patterns, or creating procedural graphics.

Features

• Generate three different image formats (PBM, PGM, PPM)
• Customizable dimensions with automatic validation
• Support for both ASCII and binary (raw) output formats
• Automatic color channel extraction for PPM images
• Fast and lightweight with minimal dependencies
• Comprehensive input validation and error handling

Quick Start

# Build the project
cd main
make all

# Generate a black and white pattern
./main 1 120 120 output.pbm 0

# Generate a grayscale gradient
./main 2 200 200 gradient.pgm 0

# Generate a colorful image
./main 3 120 120 colors.ppm 1

Building the Project

Navigate to the main directory and use the provided Makefile:

cd main
make all

To clean build artifacts:

make clean

To clean generated images:

make cleanPNM    # Clean all image files
make cleanPBM    # Clean only PBM files
make cleanPGM    # Clean only PGM files
make cleanPPM    # Clean only PPM files

Usage

./main <img_type> <width> <height> <filename> <format>

Parameters

• img_type: Type of image to generate

  • 1 = PBM (Portable BitMap)
  • 2 = PGM (Portable GrayMap)
  • 3 = PPM (Portable PixMap)

• width: Image width in pixels

  • PBM/PGM: Must be ≥ 4 and divisible by 4
  • PPM: Must be ≥ 6 and divisible by 6

• height: Image height in pixels

  • All types: Must be ≥ 4 and divisible by 4

• filename: Output filename (e.g., output.pbm, image.pgm, color.ppm)

• format: Output format

  • 0 = ASCII (human-readable text format)
  • 1 = Raw (binary format, smaller file size)

Image Types & Patterns

PBM Images (Type 1)

Generates black and white images featuring:

• Black background
• White centered rectangle (width/2 × height/2)
• Two black diagonal lines crossing the entire image

Examples:

./main 1 120 120 pattern.pbm 0    # ASCII format
./main 1 120 120 pattern.pbm 1    # Binary format

PGM Images (Type 2)

Generates grayscale images with:

• Black background
• Centered rectangle (width/2 × height/2) with four triangular gradient sections:
  • Upper triangle: White to black gradient
  • Lower triangle: Black to white gradient
  • Left triangle: White to black gradient
  • Right triangle: Black to white gradient

Examples:

./main 2 120 120 gradient.pgm 0    # ASCII format
./main 2 200 200 gradient.pgm 1    # Binary format

PPM Images (Type 3)

Generates full-color images with multi-section gradients:

Upper half (3 vertical sections):

1. Red → White gradient
2. White → Green gradient
3. Blue → White gradient

Lower half (2 vertical sections):

1. Black → White gradient
2. White → Black gradient

Bonus: Automatically generates three separate PGM files with individual color channels:

• RED_<filename>.pgm
• GREEN_<filename>.pgm
• BLUE_<filename>.pgm

Examples:

./main 3 120 120 colors.ppm 0    # ASCII format + channel files
./main 3 120 120 colors.ppm 1    # Binary format + channel files

Dimension Constraints

Image Type	Width Constraint	Height Constraint
PBM	≥ 4 and divisible by 4	≥ 4 and divisible by 4
PGM	≥ 4 and divisible by 4	≥ 4 and divisible by 4
PPM	≥ 6 and divisible by 6	≥ 4 and divisible by 4

Testing

The Makefile includes several test targets for validation:

make testValidation  # Test input validation
make testPBM        # Generate sample PBM images
make testPGM        # Generate sample PGM images
make testPPM        # Generate sample PPM images
make testAll        # Run all tests

Error Handling

The program includes comprehensive input validation:

• ✅ Validates number of command-line arguments
• ✅ Checks image type (1, 2, or 3)
• ✅ Verifies output format (0 or 1)
• ✅ Ensures width meets type-specific constraints
• ✅ Validates height requirements
• ✅ Handles memory allocation failures
• ✅ Reports file save errors

Project Structure

main/
├── main.c          # Main program logic
├── libpnm.c        # PNM library implementation
├── libpnm.h        # PNM library header
├── makefile        # Build configuration
└── images/         # Output directory for generated images
    ├── pbm/        # PBM samples
    ├── pgm/        # PGM samples
    ├── ppm/        # PPM samples
    └── ppm_to_pgm/ # Extracted color channels

Dependencies

• Standard C library
• GCC compiler (or compatible C compiler)
• Make build system

The project includes a custom libpnm library for PNM image operations:

• libpnm.h: Data structures and function declarations
• libpnm.c: Core image generation and manipulation functions

Viewing Generated Images

View the generated images with any tool that supports Netpbm formats:

• GIMP: Full support for PBM, PGM, and PPM
• ImageMagick: Command-line image manipulation
• XnView: Cross-platform image viewer
• IrfanView: Windows image viewer
• Preview (macOS): Native support for PNM formats

Tips & Tricks

• File Size: Use raw format (1) for smaller file sizes, especially for large images
• Debugging: Use ASCII format (0) to inspect image data in a text editor
• Testing: Start with smaller dimensions (e.g., 120×120) for faster generation
• Color Analysis: Use PPM type to automatically extract RGB channels as separate grayscale images

Example Workflow

1. Build the project:

   cd main
   make all

2. Generate test patterns:

   ./main 1 120 120 test_pattern.pbm 0
   ./main 2 200 200 gradient_test.pgm 0
   ./main 3 120 120 color_test.ppm 1

3. Run comprehensive tests:

   make testAll

4. View the generated images:

   open images/pbm/square.pbm    # macOS
   # or use your preferred image viewer

License

This project is available under the terms specified in the LICENSE file.

Contributing

Contributions, issues, and feature requests are welcome! Feel free to check the issues page or submit a pull request.