Darryl A. Fleurantin

Kai Maffucci

This implementation utilizes Professor Daniels at the University of Rhode Island array2 and bitpack implementations.

Usage:

Compression:

   rpeg -c [filename]

Decompression:

   rpeg -d [filename]

Architecture:

• Data Structures:

  • RgbFloat: Represents RGB colors in floating-point format.
  • Crt: Represents color space conversion in floating-point format.
  • Avg: Enum for different types of avergaes used in quantization.
  • Quantized: Struct for quantized data with coefficients and average pb/pr.
  • EncodedQuanta: Struct for encoded quantized data used in compression and decoding.

• Modules:

  • structures.rs: Defines the data structures (RgbFloat, Crt, Avg, Quantized, EncodedQuanta) for managing data formats.

  • compression.rs: Handles RGB to CRT conversion, to DCT, averaging, quantization, encoding, and packing data into codewords.

  • decompression.rs: Extracts encoded data from codewords, reverses indexing, decoding coefficients and averages, setting pb/pr values, IDCT, and conversion from CRT to RGB.

• Compressing ppm image:

  1. Read ppm image with class crate
  2. Create array2 array of pixels from image
  3. Trim array if uneven dimensions with trim_array function and update dimensions
  4. Utilize rgb_int_array_to_rgb_float_array function to convert pixels to floats
  5. Utilize rgb_float_array_to_crt_array function to convert pixels floats to component video color space values
  6. Utilize new_quantized_array function to create an array2 of empty quantized structs
  7. Utilize dct function to perform DCT on CRT array (Y/Pb/Pr) and update the empty array2 quantized structs with the new coefficients
  8. Utilize average_pb_pr function to get average pb and pr values from CRT array and update the array2 quantized structs with the new pb and pr values
  9. Utilize new_encoded_quanta_array function to create an array2 of empty encoded quanta structs
  10. Utilize index_of_chroma_array function to convert pb and pr averages to 4-bit values from quantized structs and update empty encoded quanta structs with the new pb and pr values
  11. Utilize encode_coefficients_array function to perform quantization on quantized structs coefficients and update quanta structs with the new coefficients
  12. Utilize pack_encoded_quanta function to pack data from quanta structs into codewords
  13. Convert codewords into bytes and output with class crate

• Decompressing compressed image:

  1. Read rpeg data with class crate
  2. Convert rpeg data to codewords
  3. Convert codewords to an Array2 struct
  4. Utilize extract_encoded_data function to unpack codewords to encoded quanta array
  5. Utilize new_quantized_array function to create an array2 of empty quantized structs
  6. Utilize chroma_of_index_arrayfunction to reverse index of chroma from quanta array and update the empty quantized structs with the new pb and pr values
  7. Utilize decode_coefficients_array function to dequantized quantized coefficients from quanta array and update quantized structs with the new coefficients
  8. Utilize new_crt_array function to create empty CRT array
  9. Utilize set_pb_pr function to set pb and pr values of CRT array respective to averages from quantized structs
  10. Utilize inverse_dct function to perform inverse DCT from quantized structs and update CRT array with the new y values
  11. Utilize crt_array_to_rgb_float_array function to convert CRT array to rgb float array
  12. Utilize rgb_float_array_to_rgb_int_array function to convert rgb float array to rgb int array
  13. Convert rgb int array into pixels
  14. Create rgb image from pixels
  15. Write image to standard out