Refactor out lossless JPEG code so that it can eventually be used independently

[mcroomp]

The JPEG code is useful for writing and reading JPEG files without any loss of fidelity. This can be useful for other things, such as lossless rotation, 8:1 thumbnails etc.

As a first step, remove the dependences on Lepton code and put into own module.

Copilot reviewed 12 out of 25 changed files in this pull request and generated no suggestions.

Files not reviewed (13)

• package/Lepton.Jpeg.Rust.nuspec: Language not supported
• src/structs/idct.rs: Evaluated as low risk
• src/jpeg/mod.rs: Evaluated as low risk
• src/jpeg/row_spec.rs: Evaluated as low risk
• src/structs/lepton_encoder.rs: Evaluated as low risk
• src/structs/lepton_decoder.rs: Evaluated as low risk
• src/structs/block_context.rs: Evaluated as low risk
• src/jpeg/jpeg_position_state.rs: Evaluated as low risk
• src/jpeg/block_based_image.rs: Evaluated as low risk
• src/jpeg/jpeg_write.rs: Evaluated as low risk
• src/structs/lepton_file_reader.rs: Evaluated as low risk
• src/jpeg/truncate_components.rs: Evaluated as low risk
• src/jpeg/bit_writer.rs: Evaluated as low risk

Comments skipped due to low confidence (2)

src/jpeg/jpeg_header.rs:48

• [nitpick] The error message 'invalid header encountered' is unclear. Suggest changing it to 'Invalid JPEG header encountered: expected 0xFF but found {header[0]}'.

return err_exit_code(ExitCode::UnsupportedJpeg, "invalid header encountered");

src/jpeg/jpeg_header.rs:61

• [nitpick] The error message 'segment is too short' is unclear. Suggest changing it to 'JPEG segment size is too short: expected at least 2 bytes but found {segment_size}'.

return err_exit_code(ExitCode::UnsupportedJpeg, "segment is too short");

[Melirius]

Nice work! But large, so it'll take some time to review.

[Melirius]

Finally have checked. Nice work.