Module marker 

JPEG marker parsing and iteration.

Walks the marker segments in a JPEG byte stream, extracting headers (DQT, DHT, SOF, DRI, SOS) and preserving unknown markers verbatim. Stops at the SOS marker, returning the byte offset where entropy-coded scan data begins.

Structs

MarkerEntry

Parsed marker with position information.

MarkerSegment

A raw marker segment preserving the original bytes.

SosParams

Spectral selection and successive approximation parameters from an SOS header.

Constants

COM

DHT

DQT

DRI

EOI

SOF0

SOF2

SOI

JPEG marker constants.

SOS

Functions

iterate_markers

Iterate over JPEG markers from a byte slice.

iterate_markers_all

Iterate markers for a progressive JPEG file, handling multiple scans.

parse_dri

Parse DRI (Define Restart Interval) marker data.

parse_sos

Parse an SOS (Start of Scan) header. Returns component selectors: (component_id, dc_table_id, ac_table_id) per scan component.

parse_sos_params

Parse the spectral selection / successive approximation parameters from an SOS header. These are the last 3 bytes of the SOS header data: Ss, Se, Ah_Al.

skip_scan_data

Skip past entropy-coded scan data to find the next marker.