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M11: Export ▸ Images decodes JBIG2 images

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JBIG2 images, and JBIG2 stencil masks, were reported as "can't be exported
yet", so an image the Optimizer stores as JBIG2 would stop exporting. They
are now decoded with hayro-jbig2 (already in the tree through hayro), with
their /JBIG2Globals from a DecodeParms dictionary or array, as JBIG2Decode
gives them: black as 0 (ISO 32000-2 §7.4.7). Unreadable globals, a JBIG2
page of another width, or fewer rows than the image skip the image; rows
past its height are dropped, so the output is bounded by the checked size.

docs/pdf-spec-parity.md §7.4 no longer says there is no JBIG2 encoding.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BfMGHQNgdq5yf5tKZHGR3z
This commit is contained in:
Grzegorz Martens
2026-10-29 20:47:53 +01:00
co-authored by Claude Opus 5.5
parent 5c4cadce59
commit a069003782
13 changed files with 209 additions and 17 deletions
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parity/acrobat-features.toml
+2 -2
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@@ -7164,8 +7164,8 @@ milestone = "M10"
status = "shipped"
commands = ["export.all_images"]
tools = ["doc_export_all_images"]
evidence = ["crates/create/src/tests.rs::images_export_as_jpeg_unchanged_and_others_as_png", "crates/create/src/tests.rs::indexed_and_one_bit_images_decode", "crates/create/src/tests.rs::jpeg_images_with_a_soft_mask_export_as_png_with_alpha", "crates/create/src/tests.rs::soft_masks_of_another_size_and_stencil_and_colour_key_masks_become_alpha", "crates/create/src/tests.rs::soft_mask_decode_ranges_become_exported_alpha", "crates/create/src/tests.rs::soft_mask_decode_maps_packed_and_jpeg_masks_before_resizing", "crates/automation/tests/it/automation.rs::exporting_all_images_through_tools", "crates/ui-egui/tests/it/export.rs::export_dialogs_write_images_and_text", "crates/create/src/tests.rs::lossless_decode_maps_each_component_before_colour_conversion", "crates/create/src/tests.rs::lossless_indexed_decode_rounds_in_index_units_then_clamps"]
notes = "each image once (page resources and nested forms); JPEG unchanged unless it has transparency, others PNG (gray/RGB/CMYK/ICC/Indexed, 1–16 bpc, stencil masks); transparency as PNG alpha: /SMask (scaled to the image size, /Matte un-blended), stencil /Mask and colour-key /Mask, JPEG images included (#645); JPX/JBIG2/CCITT masks are left out (image exported opaque); JPX/JBIG2/CCITT/separations reported as skipped; minimum size filter. Lossless images apply per-component Decode; Indexed values round and clip before palette lookup. Missing, null or malformed Decode arrays keep the default mapping. Soft-mask Decode intervals preserve opacity before resizing, including indirect arrays and endpoints. Still limited: 16-bit samples use high bytes; general JPEG image Decode, ICC transforms, and calibrated colors remain unsupported."
evidence = ["crates/create/src/tests.rs::images_export_as_jpeg_unchanged_and_others_as_png", "crates/create/src/tests.rs::indexed_and_one_bit_images_decode", "crates/create/src/tests.rs::jpeg_images_with_a_soft_mask_export_as_png_with_alpha", "crates/create/src/tests.rs::soft_masks_of_another_size_and_stencil_and_colour_key_masks_become_alpha", "crates/create/src/tests.rs::soft_mask_decode_ranges_become_exported_alpha", "crates/create/src/tests.rs::soft_mask_decode_maps_packed_and_jpeg_masks_before_resizing", "crates/automation/tests/it/automation.rs::exporting_all_images_through_tools", "crates/ui-egui/tests/it/export.rs::export_dialogs_write_images_and_text", "crates/create/src/tests.rs::lossless_decode_maps_each_component_before_colour_conversion", "crates/create/src/tests.rs::lossless_indexed_decode_rounds_in_index_units_then_clamps", "crates/create/src/tests.rs::jbig2_images_export_as_their_picture", "crates/automation/tests/it/automation.rs::doc_optimize_stores_black_and_white_images_as_jbig2"]
notes = "each image once (page resources and nested forms); JPEG unchanged unless it has transparency, others PNG (gray/RGB/CMYK/ICC/Indexed, 1–16 bpc, stencil masks); transparency as PNG alpha: /SMask (scaled to the image size, /Matte un-blended), stencil /Mask and colour-key /Mask, JPEG images included (#645); JBIG2 images and masks decode (JBIG2 as the only filter, with /JBIG2Globals; a JBIG2 page of another width is skipped); JPX/CCITT masks are left out (image exported opaque); JPX/CCITT/separations, and JBIG2 inside other filters, reported as skipped; minimum size filter. Lossless images apply per-component Decode; Indexed values round and clip before palette lookup. Missing, null or malformed Decode arrays keep the default mapping. Soft-mask Decode intervals preserve opacity before resizing, including indirect arrays and endpoints. Still limited: 16-bit samples use high bytes; general JPEG image Decode, ICC transforms, and calibrated colors remain unsupported."
[[feature]]
id = "create.export-html"