From abae2472d3240dd3e5cc9f67e672e7ac5c5655b5 Mon Sep 17 00:00:00 2001 From: Grzegorz Martens Date: Mon, 26 Oct 2026 18:12:37 +0100 Subject: [PATCH] M11: the crate docs, doc_optimize's mono and the M11 row name what the black-and-white step does now The optimize crate doc and MonoSettings named only 1-bit, CCITT and eight-bit grey images; doc_optimize's mono said Group 4 only; the M11 milestone row stopped at Group 4 compression. They now include downsampling (halftones aside), Group 3 to Group 4, 1-bit Flate, and black-and-white RGB and indexed images that use only palette entries 0 and 1, packed to one bit. That last isn't "two-entry", as the roadmap and the downsampling parity note had it: an indexed image packs whatever its palette's size, when its samples are 0 and 1. The mono-compression note says byte-aligned Group 3 with end-of-line codes but none before the first row is stored again as PdfCraft draws it, which at /K 0 may be other rows than were coded. From reviews with the pdfcraft-review skill. Co-Authored-By: Claude Opus 5.5 Claude-Session: https://claude.ai/code/session_01P6yUtvWGPsJpMLyh6pxSXG --- crates/automation/src/tools.rs | 2 +- crates/optimize/src/lib.rs | 14 ++++++++------ docs/roadmap.md | 4 ++-- parity/acrobat-features.toml | 4 ++-- 4 files changed, 13 insertions(+), 11 deletions(-) diff --git a/crates/automation/src/tools.rs b/crates/automation/src/tools.rs index 838fa57ab4..45471f47df 100644 --- a/crates/automation/src/tools.rs +++ b/crates/automation/src/tools.rs @@ -1433,7 +1433,7 @@ pub fn tools() -> Vec { .with(schema(json!({ "doc": doc() }), &["doc"])), t("doc_open_revision", "Open a revision", "Open saved revision `revision` (1 = the oldest) of a document as a new, unsaved document, to see the file as it was then.") .with(schema(json!({ "doc": doc(), "revision": { "type": "integer", "minimum": 1 } }), &["doc", "revision"])), - t("doc_optimize", "Optimize PDF", "Write an optimized copy to `path` (Acrobat's PDF Optimizer). preset: standard (default; Reduce File Size's choices) or mobile (images to 96 ppi above 144, JPEG high quality); the options below change it. compatibility: retain (default; keeps the document's version, or 1.5 when object streams are written), 1.4, 1.5, 1.6, 1.7 or 2.0. merge_fragments (default true) first puts a page picture drawn as many stacked image strips (as some PDF printers write it) back together into one image, so it can be resampled (merged_images, fragments_merged). color / gray: { downsample, ppi, above_ppi, compression: jpeg|zip|retain, quality 1–100 } (defaults: downsample to 150 ppi above 225, JPEG 60). mono: { downsample, ppi, above_ppi, compression: ccitt_g4|retain } for black-and-white images and image masks (default: averaged down to 300 ppi above 450 ppi, counted in images_resampled; stored losslessly as CCITT Group 4 when that is smaller, counted in images_recompressed; retain resamples only, a CCITT image staying CCITT and any other becoming Flate). Images are measured where pages draw them and replaced only when smaller. discard_*: thumbnails (default true), alternate_images (true), tags, print_settings; flate_unencoded (true); object_streams (default true; always off for 1.4); lzw_to_flate (true) decodes LZW streams and stores them with Flate instead, leaving any it cannot decode unchanged (lzw_streams counts the streams converted); remove_invalid_links and remove_unreferenced_dests (true); images and forms the pages list but never draw are always dropped (unused_xobjects). discard: Remove Hidden Information categories (metadata, attachments, comments, form-fields, hidden-text, hidden-layers, bookmarks, links-actions-scripts, private-data). Signed documents are refused. The open document is unchanged.") + t("doc_optimize", "Optimize PDF", "Write an optimized copy to `path` (Acrobat's PDF Optimizer). preset: standard (default; Reduce File Size's choices) or mobile (images to 96 ppi above 144, JPEG high quality); the options below change it. compatibility: retain (default; keeps the document's version, or 1.5 when object streams are written), 1.4, 1.5, 1.6, 1.7 or 2.0. merge_fragments (default true) first puts a page picture drawn as many stacked image strips (as some PDF printers write it) back together into one image, so it can be resampled (merged_images, fragments_merged). color / gray: { downsample, ppi, above_ppi, compression: jpeg|zip|retain, quality 1–100 } (defaults: downsample to 150 ppi above 225, JPEG 60). mono: { downsample, ppi, above_ppi, compression: ccitt_g4|retain } for black-and-white images and image masks (default: averaged down to 300 ppi above 450 ppi, counted in images_resampled; stored losslessly as CCITT Group 4 (or 1-bit Flate, once resampled or packed from more bits) when that is smaller, Group 3 fax images, black-and-white RGB and indexed images using only palette entries 0 and 1 among them, counted in images_recompressed; retain resamples only, a CCITT image staying CCITT and any other becoming Flate). Images are measured where pages draw them and replaced only when smaller. discard_*: thumbnails (default true), alternate_images (true), tags, print_settings; flate_unencoded (true); object_streams (default true; always off for 1.4); lzw_to_flate (true) decodes LZW streams and stores them with Flate instead, leaving any it cannot decode unchanged (lzw_streams counts the streams converted); remove_invalid_links and remove_unreferenced_dests (true); images and forms the pages list but never draw are always dropped (unused_xobjects). discard: Remove Hidden Information categories (metadata, attachments, comments, form-fields, hidden-text, hidden-layers, bookmarks, links-actions-scripts, private-data). Signed documents are refused. The open document is unchanged.") .cmd("optimize.advanced") .with(schema( json!({ diff --git a/crates/optimize/src/lib.rs b/crates/optimize/src/lib.rs index a8a24b6aed..3a920d1f13 100644 --- a/crates/optimize/src/lib.rs +++ b/crates/optimize/src/lib.rs @@ -10,10 +10,11 @@ //! A new image replaces the old one only if it is smaller. The colour and grey settings leave //! alone images they can't decode faithfully (CMYK and other colour spaces, masks, decode arrays //! other than the default, JPEG 2000, JBIG2, CCITT, other than 8 bits, JPEGs whose Adobe marker -//! and `/ColorTransform` disagree). Black-and-white images (1-bit, image masks -//! and CCITT fax among them, and eight-bit grey of only black and white) above a threshold are -//! averaged down to a target resolution, halftones and dithers aside, and are stored as CCITT -//! Group 4 when that is smaller. +//! and `/ColorTransform` disagree). Black-and-white images (1-bit, image masks and CCITT fax, +//! Group 3 among them; and eight-bit grey and RGB of only black and white, and indexed images +//! that use only palette entries 0 and 1, packed to one bit) above a threshold are averaged down to a +//! target resolution, halftones and dithers aside, and are stored as CCITT Group 4, or 1-bit +//! Flate once resampled or packed, when that is smaller. //! - **Discard objects:** page thumbnails, alternate images, document tags (structure tree), //! print settings. //! - **Clean up:** drop images and forms that pages list but never draw (such as a deleted @@ -130,8 +131,9 @@ pub enum MonoCompression { Retain, } -/// How black-and-white images (1-bit, CCITT fax among them, and eight-bit grey of only black -/// and white), and image masks, are resampled and stored. +/// How black-and-white images (1-bit, CCITT fax among them; and eight-bit grey and RGB of only black +/// and white, and indexed images that use only palette entries 0 and 1, packed to one bit), and +/// image masks, are resampled and stored. #[derive(Clone, Copy, Debug, PartialEq)] pub struct MonoSettings { /// Average images whose effective resolution is above `above_ppi` down to `target_ppi`. diff --git a/docs/roadmap.md b/docs/roadmap.md index 1cef4f5965..f5d3d1b44b 100644 --- a/docs/roadmap.md +++ b/docs/roadmap.md @@ -2,7 +2,7 @@ > **Last reviewed:** 2026-10-27 | **Last updated:** 2026-10-27 | **Change:** minor (M10: OCR model downloads use verified ONNX pairs with legacy discovery fallback; estimates unchanged) > **Last reviewed:** 2026-10-25 | **Last updated:** 2026-10-25 | **Change:** minor (M14 localization current state: Arabic logical catalog, explicit RTL label direction and mirrored stock chrome; native/browser RTL workflows unqualified. Native release Hans face via LXGW WenKai Lite; estimates unchanged) -> **Last reviewed:** 2026-10-24 · **Last updated:** 2026-10-24 · **Change:** minor (M11: the optimizer stores Group 3 fax images as Group 4, and packs black-and-white RGB and two-entry indexed images to one bit; estimates unchanged) +> **Last reviewed:** 2026-10-24 · **Last updated:** 2026-10-24 · **Change:** minor (M11: the optimizer stores Group 3 fax images as Group 4, and packs black-and-white RGB and indexed images that use only palette entries 0 and 1 to one bit; estimates unchanged) > **Last reviewed:** 2026-10-24 · **Last updated:** 2026-10-24 · **Change:** minor (M11: black-and-white images above 450 ppi are averaged down to 300 ppi by the optimizer; estimates unchanged) > **Last reviewed:** 2026-10-24 · **Last updated:** 2026-10-24 · **Change:** minor (M11: black-and-white pictures stay one bit when PDFs are created and optimized; CCITT images export; estimates unchanged) > **Last reviewed:** 2026-10-23 · **Last updated:** 2026-10-23 · **Change:** minor (M11: the PDF Optimizer and Reduce File Size store black-and-white images as CCITT Group 4 when smaller; estimates unchanged) @@ -199,7 +199,7 @@ total matches the parity estimate. | M8 | Security + redaction | 100–180 | 68% | 15–30 | Done: opening protected documents, permissions, Protect Using Password, Remove security; redaction (mark text/areas/pages, Search & Redact with patterns, apply removing glyphs, image pixels, vectors, XObject content, annotations and fields, verification, full rewrite on save); Remove hidden information and Sanitize.
Done since: redaction codes (U.S. FOIA and Privacy Act sets as overlay text, in Redaction properties and `redact_mark`). Redaction cleans indirect and form structure references, preserving surviving form tags. Redaction retires inherited resource dictionaries, so a parent `/Pages` can't keep a removed XObject reachable; unredacted pages are left untouched. Image redaction removes alternate images and unsupported masks only on affected images. Changed marked-content spans lose replacement descriptions; untouched spans keep theirs. Hidden-text cleanup retires unused named descriptions across inherited/shared page and form resources (64 focused tests and scoped Rust 1.96 Clippy/wasm checks pass; publication CI pending). The redaction audit counts a filled cover that hides half of any one word of a long line (#2662), applied or not. Phone-pattern redaction also matches labelled Italian geographic numbers with `+39` and a slash after the area code (#3205 follow-up); unlabelled international slash numbers remain unsupported. Missing: certificate security, custom redaction code sets and pattern locales, DCT re-encoding | | M9 | Signatures (PAdES, validation) | 160–280 | 60% | 40–70 | Done: new `sign` crate (DER, X.509, CMS, PKCS #12 on RustCrypto; aws-lc-rs for RSA private keys); PAdES B-B signing (visible, invisible, existing fields, certification with DocMDP); validation with trust store and changes-after-signing classification; self-signed digital IDs; Signatures panel, message bar, sign dialogs; agent tools. Checked with pdfsig and OpenSSL.
Done since: macOS Keychain and Windows Current User Personal store signing (software-backed CNG keys), certificate viewer, signed documents protected from rewrites, page validation overlays separate from original signature artwork (baked Not Verified captions remain; #79 open), snapshot tabs that reuse instead of multiplying. Missing: timestamps (B-T), LTV (DSS, OCSP, CRL), FieldMDP, smart cards, PKCS #11 | | M10 | OCR, create, export, print | 200–350 | 33% | 120–215 | Done: create from blank/text/PNG/JPEG/TIFF (multi-page)/GIF/BMP; export PNG/JPEG/TIFF and text; Print (Acrobat's sizing, n-up, booklet, poster, comments & forms, preview, the CUPS and Windows spoolers, print-ready PDF).
Done since: embedded/72/custom DPI choices for image imports; export all images; OCR (searchable image for pages, ranges and multiple files); single-sided cut-and-stack imposition with cut marks, through Print and doc_print; architectural/ANSI/large ISO sheet presets, Match page at 100% and PDF-scale preview (#599 follow-up); Create PDF from multiple files (PDFs, images and text, edited as pages in the grid); OCR can also read pictures on pages that have text, without adding that text twice (#1028). Model staging fetches SHA-256-verified ONNX detection/recognition files after the upstream RTEN URL brownout; runtime discovery prefers complete ONNX pairs per directory, then complete legacy RTEN pairs, without mixing formats or changing directory precedence. Done since: Word invoice export uses borderless inferred tables, floating positioned text/artwork only where text overlaps an image or is rotated, and per-page sizes, covered by synthetic invoice automation regressions (#773); printing on the web through the browser's print dialog, sheets drawn by PdfCraft (gap 4). Lossless image export applies per-component Decode, including Indexed mapping (#1201 partial). Existing 16-bit precision and color-management limits remain. #3532 partial: vector printing retains existing appearances with absent Subtype through a print-owned Form copy; source artwork stays unchanged. #3120: Office export reads form XObjects 50 levels deep, as the renderer does, and up to 50 000 a page; pages past that are listed in `truncated_pages`. Word table cells use the grid columns they span, including cells after a merged cell. Done since: text in a table slot covered by another cell's span remains as paragraph text in Word, HTML, RTF and PowerPoint. Missing: OCR languages beyond Latin, editable-text OCR output, full Office layout fidelity/import. Done since: dotted-leader contents entries stay in separate complete paragraphs (#1757) #2156 candidate: last selected print paper persists across sessions; other print preferences unchanged. Image export applies soft-mask Decode opacity intervals before resizing, including indirect entries and inverted ranges. Vector printing gives annotation appearances unoccupied XObject names so existing page artwork survives. | -| M11 | Optimize, preflight, PDF/A/X/UA, print production | 200–350 | 18% | 80–140 | Done: new `optimize` crate: Reduce File Size and the PDF Optimizer (images measured where drawn, bicubic downsampling, JPEG/ZIP recompression only when smaller, discard objects and user data, Flate clean-up, resource merging, object streams). Target-version compatibility is partial: newer content is not detected or converted. Content stream boundaries preserve comments, split operands and graphics state when image fragments merge. Image downsampling includes page-local `/UserUnit` scaling when measuring physical resolution. Done since: reject invalid image and soft-mask dimensions with checked sizing (#2178); black-and-white images stored losslessly as CCITT Group 4 when smaller. Missing: fonts and transparency panels, space audit, preflight, PDF/A/X/UA | +| M11 | Optimize, preflight, PDF/A/X/UA, print production | 200–350 | 18% | 80–140 | Done: new `optimize` crate: Reduce File Size and the PDF Optimizer (images measured where drawn, bicubic downsampling, JPEG/ZIP recompression only when smaller, discard objects and user data, Flate clean-up, resource merging, object streams). Target-version compatibility is partial: newer content is not detected or converted. Content stream boundaries preserve comments, split operands and graphics state when image fragments merge. Image downsampling includes page-local `/UserUnit` scaling when measuring physical resolution. Done since: reject invalid image and soft-mask dimensions with checked sizing (#2178); black-and-white images stored losslessly as CCITT Group 4 when smaller, averaged down to 300 ppi above 450 (halftones aside), Group 3 stored again as Group 4, and black-and-white RGB and indexed images that use only palette entries 0 and 1 packed to one bit. Missing: fonts and transparency panels, space audit, preflight, PDF/A/X/UA | | M12 | Accessibility, compare, measure, search, XFA | 200–380 | 30% | 90–160 | Done: new `a11y` crate with the Accessibility Checker (all 32 rules, report, Fix/Skip/Explain, options dialog and results panel, agent tools). Locatable figure, annotation and form findings highlight their page bounds. Character encoding accepts Identity-H/V with Adobe CJK collections and predefined CJK CMaps independently (#3673); per-glyph validation and embedded-font extraction remain separate.
Done since: 2D distance, perimeter and area measurements with persistent viewport calibration, snapping, live information and CSV export; a bounded, text-only auto-tag proposal tool for one page. Marking a figure decorative rewrites only that stream (#1324). An XFA radio item whose value contains a space is written back unchanged (#1319). Done since: #2569: Growable multiline XFA text reflows after edits, with undo/redo, save/reopen and print coverage; oversized fields still become read-only page text. Structured-data synchronization warnings retain accepted whitespace without relayout from stale data. Done since: #2572: Every repeated page-master button resolves its own field to the shared XFA click script, including print buttons. Done since: #2570: Dynamic XFA rich-text fields carry exData/maxLength into AcroForm MaxLen for reported and enforced Unicode character limits, retained after save/reopen. Done since: #2589: Active XFA skips PDF-container fallback scripts while retaining requested messages and saved scripts; ordinary/static/unlaid-out documents and explicit console/field calls keep their existing behavior. Missing: writing proposed tags and parent tree, field autotag, visual Tags/Order/Content panels, Reading Order tool, compare, geospatial/3D measurement, search index, XFA
Reading colours: pending page backgrounds follow the configured colour (#2059). | | M13 | Automation (MCP, Action Wizard, CLI) + AI providers | 60–120 | 45% | 25–45 | Done: MCP resources (document info, text, page images); headless tool table (123 tools incl. signing, optimizing, initial view, links, stamps, data exchange, comment review, forms authoring and scripts, redaction, sanitize, print, add content), opt-in MCP server over stdio, CLI `run`/`tools` (closed stdout pipes exit cleanly), UI control channel with drag. Missing: Action Wizard, AI providers
Done since: CLI run and MCP reject missing, empty, repeated and option-valued --root arguments before any tool/script execution or MCP initialization. A single-hyphen directory name remains valid; synthetic CLI regressions preserve a would-be overwritten file. `text_find` also caps the per-page match ranges it materializes at the remaining result limit plus one continuation match. CLI robustness scans visit each directory once through overlapping roots and symlink aliases. | | M12 | Accessibility, compare, measure, search, XFA | 200–380 | 30% | 90–160 | Done: new `a11y` crate with the Accessibility Checker (all 32 rules, report, Fix/Skip/Explain, options dialog and results panel, agent tools). Locatable figure, annotation and form findings highlight their page bounds. Character encoding accepts Identity-H/V with Adobe CJK collections and predefined CJK CMaps independently (#3673); per-glyph validation and embedded-font extraction remain separate.
Done since: 2D distance, perimeter and area measurements with persistent viewport calibration, snapping, live information and CSV export; a bounded text-only auto-tag proposal tool; text-only Apply writes marked content, paragraph tags and a parent tree, then opens the Tags panel for review. Missing: mixed-content and field autotag, heading/list/table/figure classification, Order/Content panels, Reading Order tool, compare, geospatial/3D measurement, search index, XFA
Done since: CLI info, text and render use dynamic XFA layout pages, with synthetic count/text/pixel and copy-permission regressions (#1645).
Reading colours: pending page backgrounds follow the configured colour (#2059). | diff --git a/parity/acrobat-features.toml b/parity/acrobat-features.toml index 6cc4f4797c..99deb812bc 100644 --- a/parity/acrobat-features.toml +++ b/parity/acrobat-features.toml @@ -7361,7 +7361,7 @@ status = "partial" commands = ["optimize.advanced"] tools = ["doc_optimize"] evidence = ["crates/optimize/tests/optimize.rs::images_are_measured_where_drawn_and_downsampled", "crates/optimize/tests/optimize.rs::settings_choose_what_happens", "crates/automation/tests/it/automation.rs::optimizing_through_tools", "crates/optimize/tests/optimize.rs::a_page_picture_printed_as_one_pixel_strips_is_merged_into_one_image", "crates/optimize/tests/optimize.rs::images_that_do_not_tile_a_picture_are_left_alone", "crates/optimize/tests/optimize.rs::a_deeply_nested_form_is_measured_at_its_largest_use", "crates/optimize/tests/optimize.rs::images_are_not_resampled_when_some_uses_could_not_be_measured", "crates/optimize/tests/optimize.rs::image_resolution_uses_the_pages_physical_unit", "crates/optimize/tests/optimize.rs::optimization_retains_an_image_below_threshold_on_a_scaled_page", "crates/optimize/tests/optimize.rs::shared_forms_are_measured_in_each_pages_physical_units", "crates/optimize/tests/optimize.rs::black_and_white_images_above_450_ppi_are_averaged_down_to_300", "crates/optimize/src/images.rs::it_matches_the_slow_way", "crates/automation/tests/it/automation.rs::doc_optimize_averages_black_and_white_scans_down", "crates/ui-egui/tests/it/create.rs::the_pdf_optimizer_dialog_saves_an_optimized_copy"] -notes = "colour and grayscale, bicubic, effective resolution measured where drawn (every use, with page-local UserUnit scaling, through nested forms up to 12 deep; when a use can't be measured, nothing is resampled); image fragments stacked edge to edge are merged first (side-by-side tiles not yet); monochrome (1-bit, CCITT fax, and eight-bit black-and-white grey and RGB and indexed images of two palette entries) averaged by area to 300 ppi above 450 ppi by default, a tie to the dark sample (black in grey, painted in a mask, ink in a separation, after the decode array; an indexed image's entry 0, its palette not read yet), then stored as Group 4 or 1-bit Flate (Monochrome Images ▸ Downsample to; doc_optimize mono); not monochrome images with a soft mask, halftones and dithers (most of their new pixels would cover both black and white, and their tones turn solid), or images wider than a fax row (1,048,576 samples), and Acrobat's bicubic and subsampling choices for monochrome aren't offered" +notes = "colour and grayscale, bicubic, effective resolution measured where drawn (every use, with page-local UserUnit scaling, through nested forms up to 12 deep; when a use can't be measured, nothing is resampled); image fragments stacked edge to edge are merged first (side-by-side tiles not yet); monochrome (1-bit, CCITT fax, and eight-bit black-and-white grey and RGB, and indexed images that use only palette entries 0 and 1) averaged by area to 300 ppi above 450 ppi by default, a tie to the dark sample (black in grey, painted in a mask, ink in a separation, after the decode array; an indexed image's entry 0, its palette not read yet), then stored as Group 4 or 1-bit Flate (Monochrome Images ▸ Downsample to; doc_optimize mono); not monochrome images with a soft mask, halftones and dithers (most of their new pixels would cover both black and white, and their tones turn solid), or images wider than a fax row (1,048,576 samples), and Acrobat's bicubic and subsampling choices for monochrome aren't offered" [[feature]] id = "optimize.recompress-images" @@ -7385,7 +7385,7 @@ status = "partial" commands = ["optimize.advanced", "optimize.reduce"] tools = ["doc_optimize", "doc_reduce"] evidence = ["crates/optimize/tests/optimize.rs::eight_bit_black_and_white_images_become_one_bit", "crates/filters/src/ccitt.rs::bitmaps_round_trip", "crates/filters/src/ccitt.rs::a_page_of_text_like_marks_round_trips_and_shrinks", "crates/filters/src/ccitt.rs::what_it_cannot_encode_is_an_error", "crates/optimize/tests/optimize.rs::black_and_white_images_become_ccitt_group_4", "crates/optimize/tests/optimize.rs::group_3_fax_images_become_group_4", "crates/optimize/tests/optimize.rs::rgb_and_two_colour_indexed_black_and_white_images_become_one_bit", "crates/automation/tests/it/automation.rs::doc_optimize_stores_black_and_white_images_as_ccitt_group_4", "crates/ui-egui/tests/it/create.rs::the_pdf_optimizer_dialog_saves_an_optimized_copy"] -notes = "CCITT Group 4, lossless: PDF Optimizer ▸ Images ▸ Monochrome Images (on by default, so Reduce File Size does it too; doc_optimize mono) stores a 1-bit image of one colour component (grey, indexed, a separation) or an image mask, kept with no filter or general-purpose ones, as Group 4 when that is smaller as stored; the samples decode to the same bits, so colour space, decode array and masks stay. Packed to one bit first, then stored the same way (colour-key masks aside): eight-bit grey of only black and white, eight-bit DeviceRGB of only black and white (as DeviceGray; calibrated RGB, RGB with a profile, RGB drawn where /DefaultGray or /DefaultRGB is in force, and RGB whose soft mask has a /Matte aside), and an indexed image of 2, 4 or 8 bits that uses only palette entries 0 and 1 (keeping its palette), unless the grey or colour settings make it smaller still, as they can a dithered scan downsampled to JPEG, its soft mask counted. Group 4 wins on scans; on clean computer-drawn 1-bit art Flate can be smaller, and the image then stays. Group 3 fax images are stored again as Group 4 when that is smaller (damaged Group 3 with end-of-line codes as the decoder recovers it, as it reports no damage there). CCITT fax images are decoded to be downsampled (optimize.downsample-images), and a resampled image is stored as Group 4 or 1-bit Flate, whichever is smaller. Not yet: JBIG2 (lossless or lossy, which Adobe's help says beats CCITT for monochrome), inline images, soft masks and /Mask images, Group 4 for rows wider than 32,767 samples." +notes = "CCITT Group 4, lossless: PDF Optimizer ▸ Images ▸ Monochrome Images (on by default, so Reduce File Size does it too; doc_optimize mono) stores a 1-bit image of one colour component (grey, indexed, a separation) or an image mask, kept with no filter or general-purpose ones, as Group 4 when that is smaller as stored; the samples decode to the same bits, so colour space, decode array and masks stay. Packed to one bit first, then stored the same way (colour-key masks aside): eight-bit grey of only black and white, eight-bit DeviceRGB of only black and white (as DeviceGray; calibrated RGB, RGB with a profile, RGB drawn where /DefaultGray or /DefaultRGB is in force, and RGB whose soft mask has a /Matte aside), and an indexed image of 2, 4 or 8 bits that uses only palette entries 0 and 1 (keeping its palette), unless the grey or colour settings make it smaller still, as they can a dithered scan downsampled to JPEG, its soft mask counted. Group 4 wins on scans; on clean computer-drawn 1-bit art Flate can be smaller, and the image then stays. Group 3 fax images are stored again as Group 4 when that is smaller (damaged Group 3 with end-of-line codes as the decoder recovers it, as it reports no damage there; byte-aligned Group 3 with end-of-line codes but none before the first row, not as T.4 sends them, as PdfCraft draws it, which at /K 0 may be other rows than were coded). CCITT fax images are decoded to be downsampled (optimize.downsample-images), and a resampled image is stored as Group 4 or 1-bit Flate, whichever is smaller. Not yet: JBIG2 (lossless or lossy, which Adobe's help says beats CCITT for monochrome), inline images, soft masks and /Mask images, Group 4 for rows wider than 32,767 samples." [[feature]] id = "optimize.only-if-smaller"