Module texture_decode 

Image decoding pipeline – codec dispatch, RAW/HEIF/JXL/JPEG2K/SVG/PSD/WebP decoders, embedded-preview extraction, EXIF orientation, and decode-cache management.

This module was extracted from library/mod.rs to keep the main module focused on window construction and navigation.

Modules

codecs 🔒

Structs

LibrawHandle 🔒

MemImage 🔒

Enums

MarkerKind 🔒

TextureDecoder 🔒

TiffEndian 🔒

Constants

MIN_EMBEDDED_JPEG_SIZE 🔒

Minimum size for an embedded preview to be considered – tiny thumbnails (EXIF 160x120 stubs) are almost always useless and should be skipped in favour of the full-resolution preview or the libraw fallback.

Statics

RAW_CACHE_ENABLED 🔒

Runtime flag controlling the on-disk RAW decode cache. Initialised from config at startup; toggled live from the settings UI.

RAW_FULL_DECODE 🔒

Runtime flag: true = full demosaic, false = extract embedded JPEG preview.

Functions

apply_exif_orientation 🔒

Apply EXIF orientation (1..=8) to a Pixbuf via rotate + optional flip.

apply_libraw_flip 🔒

Apply libraw flip orientation to a Pixbuf.

choose_best_embedded_jpeg 🔒

classify_jpeg_marker 🔒

configure_libraw_full_decode 🔒 ^⚠

decode_full_raw_texture 🔒

decode_heif_texture 🔒

decode_image_texture 🔒

decode_jpeg_texture 🔒

decode_libraw_bitmap_thumb 🔒

Decode a bitmap (uncompressed RGB) thumbnail extracted by libraw.

decode_libraw_jpeg_thumb 🔒

Decode a JPEG thumbnail extracted by libraw.

decode_libraw_texture 🔒

Decode a RAW via vendored libraw with camera white balance + AHD demosaic at full resolution. Output goes through a disk cache keyed by (path, mtime, size) so a re-open hits the cache instead of re-demosaicing.

decode_libraw_uncached 🔒

decode_pixbuf_texture 🔒

decode_psd_texture 🔒

decode_raw_preview_or_fallback 🔒

decode_raw_texture 🔒

decode_raw_thumbnail_texture 🔒

Thumbnail-targeted RAW decode: embedded JPEG first, full demosaic only as last resort. Ignores RAW_FULL_DECODE (which is for lightbox quality, not 256-px grid tiles – full sensor data would just be scaled away).

decode_webp_texture 🔒

decode_with_fallbacks 🔒

decode_with_route 🔒

dynamic_image_texture 🔒

extract_largest_embedded_jpeg 🔒

Return the largest renderable JPEG embedded in the file, or None. Uses structure-aware marker walking; skips lossless SOF3 payloads (compressed Bayer data) and payloads below MIN_EMBEDDED_JPEG_SIZE.

extract_libraw_thumb 🔒

Embedded RAW preview: SOI-scan for the largest JPEG (primary), fall back to libraw’s bitmap/JPEG thumbnail for files that store the preview as TIFF strips (Samsung DNG, OnePlus DNG, etc.). Full demosaic path untouched.

extract_primary_embedded_jpeg 🔒

find_jpeg_end 🔒

Walk the JPEG marker structure starting at the SOI at bytes[start] and return the byte offset just past the EOI (or the end of the buffer if the file omits the trailing EOI).

has_jpeg_soi 🔒

init_libraw 🔒 ^⚠

is_embedded_jpeg_start 🔒

is_exif_segment 🔒

is_lossless_jpeg 🔒

True if the JPEG at bytes[start..end] uses SOF3 (lossless JPEG). RAW files wrap compressed Bayer data in SOF3 containers – these are never renderable and should be skipped by the preview scanner.

is_standalone_jpeg_marker 🔒

is_thumbnail_prerotated 🔒

Check whether a thumbnail has already been rotated to display orientation by the camera firmware. Compares the thumbnail’s aspect ratio to the raw sensor’s: if a 90-degree flip is needed (flip=5 or flip=6) but the thumbnail is already in the rotated aspect (portrait when sensor is landscape, or vice versa), the thumbnail is pre-rotated.

jpeg_bytes_to_oriented_texture 🔒

Decode JPEG bytes to a texture, applying EXIF orientation or libraw flip.

jpeg_segment 🔒

libraw_image_to_texture 🔒 ^⚠

libraw_step 🔒 ^⚠

load_texture_blocking 🔒

log_decode_result 🔒

make_libraw_image 🔒 ^⚠

memory_texture 🔒

parse_tiff_orientation 🔒

Parse TIFF IFD0 starting at the TIFF header, return orientation if present.

pixbuf_to_texture 🔒

Convert a Pixbuf to a gdk4::Texture (same logic as decode_pixbuf_texture).

raw_decode_cache_dir 🔒

Return the directory used for the on-disk RAW decode cache.

raw_decode_cache_key 🔒

Build a stable cache filename for a RAW file based on its canonical path, last-modified timestamp (seconds), and byte length. Any change to the file on disk produces a different key so stale pixels are never served.

read_jpeg_exif_orientation 🔒

Read EXIF orientation (tag 0x0112) from JPEG bytes. Returns 1..=8 or None. Hand-rolled because Pixbuf::apply_embedded_orientation silently drops EXIF on some RAW-embedded JPEGs (truncated/oversize APP1 segments).

read_raw_decode_cache 🔒

Attempt to load a previously cached demosaiced texture from disk. Returns None if the cache entry is absent, stale, or unreadable.

run_libraw_full_decode 🔒 ^⚠

scan_sos_entropy 🔒

Read a SOS header, then scan through entropy-coded data until the next real marker. Returns the position of that marker, or None on truncation.

seek_marker 🔒

Advance past non-marker bytes and padding 0xFF fills, returning the position of the next real marker prefix.

set_raw_cache_enabled

Update the runtime RAW cache flag (called from settings and startup).

set_raw_full_decode

Update the runtime RAW full-decode flag (called from settings and startup).

skip_or_accept 🔒

Skip a variable-length JPEG segment, or return None when the segment is malformed (signals the caller to accept the whole remaining buffer).

skip_segment 🔒

Read and skip a variable-length JPEG segment. Returns the position after the segment, or None if the segment is malformed.

texture_decoder_for_path 🔒

unpack_libraw_fallback_thumb 🔒 ^⚠

Unpack and decode the libraw fallback thumbnail (JPEG or bitmap).

write_raw_decode_cache 🔒

Persist a successfully demosaiced RAW texture to the disk cache so future opens can skip the expensive libraw pipeline entirely.

write_raw_decode_cache_async 🔒