Struct JpegImage 

pub struct JpegImage { /* private fields */ }

A decoded JPEG image providing access to quantized DCT coefficients.

Created by parsing a JPEG byte stream with JpegImage::from_bytes. After modifying DCT coefficients (e.g., for steganographic embedding), call JpegImage::to_bytes to re-encode. If coefficient modifications introduce symbols not present in the original Huffman tables, call JpegImage::rebuild_huffman_tables first.

Implementations

impl JpegImage

pub fn from_bytes(data: &[u8]) -> Result<Self>

Parse a JPEG file from bytes.

Supports both baseline (SOF0) and progressive (SOF2) JPEG. Progressive images are decoded by accumulating all scans, then the coefficients are stored exactly as in baseline — to_bytes() always writes baseline output.

pub fn to_bytes(&self) -> Result<Vec<u8>>

Encode the (possibly modified) image back to JPEG bytes.

pub fn to_bytes_with_progress( &self, on_progress: Option<&dyn Fn()>, ) -> Result<Vec<u8>>

Serialize this JPEG image to bytes, with an optional progress callback that fires approximately scan::JPEG_WRITE_STEPS times during scan encoding.

pub fn dct_grid(&self, component: usize) -> &DctGrid

Get a reference to the DCT coefficient grid for a component. Component index is in scan order (typically 0=Y, 1=Cb, 2=Cr).

pub fn dct_grid_mut(&mut self, component: usize) -> &mut DctGrid

Get a mutable reference to the DCT coefficient grid for a component.

pub fn frame_info(&self) -> &FrameInfo

Get the frame information.

pub fn quant_table(&self, id: usize) -> Option<&QuantTable>

Get a quantization table by ID.

pub fn num_components(&self) -> usize

Number of components in the scan.

pub fn rebuild_huffman_tables(&mut self)

Rebuild Huffman tables from the current coefficient data.

Call this after modifying DCT coefficients to ensure the Huffman tables can encode all symbols present in the modified data. This replaces the DHT segments in raw_segments and updates dc_huff_specs/ac_huff_specs.

pub fn set_quant_table(&mut self, id: usize, qt: QuantTable)

Replace a quantization table by ID and rebuild the DQT marker segments.

Call this after modifying DCT coefficients to reflect new quantization (e.g., for recompression simulation). Updates both the internal table and the raw DQT segments so that to_bytes() produces correct output.

Trait Implementations

impl Clone for JpegImage

fn clone(&self) -> JpegImage

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.