PNG Image Encoding

This repository contains a PNG image encoder implemented in C. It takes a BMP image as input and encodes it using PNG-like encoding, producing a compressed output file.

The encoder performs the following steps:

1. Image Loading: Loads a BMP image from the specified input file.
2. Filtering: Applies various filtering techniques to the image scanlines.
3. Encoding: Encodes the filtered image data.
4. File Output: Writes the encoded data to the specified output file, including a header and the encoded image data.

The repository has the following structure:

• include/: Contains header files, including encoder.h, which defines the image and encoder structures and function prototypes.
• src/: Contains the source code files.
  • png_encoder.c: Implements the PNG encoding logic.
  • main.c: Contains the main function that parses command-line arguments, loads the image, performs the encoding, and saves the output.
  • utils/: Contains utility functions.
    • bitstream.c: Implements bitstream reading and writing functions.
    • image.c: Implements image loading and saving functions.
• Makefile: Defines the build process for the project.
• README.md: This file, providing an overview of the project.

To build the encoder, you need a C compiler (e.g., GCC) and the make build tool.

1. Clone the repository.
2. Navigate to the repository's root directory.
3. Run the make command.

make

This will create an executable file named png-encoder in the bin directory.

To use the encoder, run the png-encoder executable with the following command-line arguments:

bin/png-encoder <input_file> <output_file> [level=0-9]

• <input_file>: The path to the input BMP image file.
• <output_file>: The path to the output file where the encoded data will be written.
• level: The PNG compression level (0-9, default: 6).

Example:

bin/png-encoder input.bmp output.png level=9

The output file format is as follows:

1. Header: "PNGL" (4 bytes)
2. Image Dimensions:
   • Width (4 bytes)
   • Height (4 bytes)
   • Channels (1 byte)
   • Compression Level (1 byte)
3. Filtered Data: The filtered image data, with each scanline prefixed by its filter type.

• Standard C library