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M11: redaction removes Group 3 on bytes whole, which the renderer may draw as other rows

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PdfCraft's bootstrap renderer draws byte-aligned Group 3 whose fill ends
each end-of-line code on a byte (as TIFF writes it) as other rows than
decode_ccitt reads (black box, at every /K, with /EndOfLine or not:
mostly the first row, then blank). Redaction cleared pixels in the
picture decode_ccitt reads, so a mark over what PdfCraft showed needn't
cover what was cleared, and content shown blank stayed in the copy. Such
an image (/K 0 or more, /EncodedByteAlign) is now removed whole, as
every CCITT image was before this PR; Group 3 off bytes and Group 4 are
still cleared.

The image's parameters come from Document::fax_params, the reading of a
fax image's /DecodeParms entry that decoded_image already did, now on
its own (it was to come with #4404, which uses it too). The redaction
README, the module doc, the redaction and core.image-filters notes and
the spec parity table's status line and revision row say so, and the
core.image-filters note now records the renderer's misdrawing.

group_3_on_bytes_is_removed_whole_and_other_fax_images_cleared: a white
16 × 2 picture, checked to decode as such, is removed whole on bytes (no
codes; codes at /K 0; at /K 1 with /EncodedByteAlign by reference) and
cleared off bytes and as Group 4 on bytes. It fails without the guard;
cargo-mutants catches every viable mutant of it.

From reviews with the pdfcraft-review skill.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01P6yUtvWGPsJpMLyh6pxSXG
This commit is contained in:
Grzegorz Martens
2026-10-29 20:48:03 +01:00
co-authored by Claude Opus 5.5
parent aaa3d815c1
commit 1ad951e25b
8 changed files with 105 additions and 41 deletions
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parity/acrobat-features.toml
+3 -3
View File
@@ -131,7 +131,7 @@ status = "partial"
commands = []
tools = []
evidence = ["crates/filters/src/ccitt.rs::decoding_gives_the_rows_back", "crates/filters/src/ccitt.rs::group_3_rows_on_bytes_read_by_the_codes_in_the_data", "crates/cos/src/document/tests.rs::fax_images_decode_with_their_parameters"]
notes = "decoded through the hayro bootstrap for display; own codecs are M1.1/M1.2. CCITT fax decoding is in filters (decode_ccitt, through hayro-ccitt), which Document::decoded_image uses for Export ▸ Images, the optimizer and redaction. Byte-aligned Group 3 is read by its end-of-line codes when the data starts with one and on bytes otherwise; still limited: data with codes but none before the first row (not as T.4 sends them) is read on bytes, as the renderer draws it, and at /K 0 may come out as other rows, which the optimizer and redaction then write back"
notes = "decoded through the hayro bootstrap for display; own codecs are M1.1/M1.2. CCITT fax decoding is in filters (decode_ccitt, through hayro-ccitt), which Document::decoded_image uses for Export ▸ Images, the optimizer and redaction. Byte-aligned Group 3 is read by its end-of-line codes when the data starts with one and on bytes otherwise; still limited: data with codes but none before the first row (not as T.4 sends them) is read on bytes, as the renderer draws it, and at /K 0 may come out as other rows, which the optimizer then writes back. The bootstrap renderer draws byte-aligned Group 3 whose fill ends each end-of-line code on a byte as other rows (black box, at every /K), which decode_ccitt reads right; redaction removes Group 3 on bytes whole"
[[feature]]
id = "core.decompression-limits"
@@ -5792,8 +5792,8 @@ milestone = "M8"
status = "shipped"
commands = ["redact.apply"]
tools = ["redact_apply"]
evidence = ["crates/redact/src/tests.rs::images_are_removed_or_have_their_pixels_cleared", "crates/redact/src/tests.rs::redaction_clears_pixels_intersected_without_covering_their_centres", "crates/redact/src/tests.rs::a_fax_image_has_its_covered_pixels_cleared_instead_of_being_removed", "crates/redact/src/tests.rs::an_image_whose_predictor_is_given_by_reference_has_the_covered_pixel_cleared"]
notes = "intersected pixel footprints are cleared conservatively in a copy, CCITT fax images (scans stored as Group 4) included; DCT/JPX/JBIG2 images removed whole"
evidence = ["crates/redact/src/tests.rs::images_are_removed_or_have_their_pixels_cleared", "crates/redact/src/tests.rs::redaction_clears_pixels_intersected_without_covering_their_centres", "crates/redact/src/tests.rs::a_fax_image_has_its_covered_pixels_cleared_instead_of_being_removed", "crates/redact/src/tests.rs::group_3_on_bytes_is_removed_whole_and_other_fax_images_cleared", "crates/redact/src/tests.rs::an_image_whose_predictor_is_given_by_reference_has_the_covered_pixel_cleared"]
notes = "intersected pixel footprints are cleared conservatively in a copy, CCITT fax images (scans stored as Group 4) included; DCT/JPX/JBIG2 images, and Group 3 on bytes (which the bootstrap renderer may draw as other rows than the decoder reads), removed whole"
[[feature]]
id = "protect.redact-vectors"