diff --git a/crates/content/README.md b/crates/content/README.md index 6ab984dd49..fedeadc56b 100644 --- a/crates/content/README.md +++ b/crates/content/README.md @@ -13,7 +13,10 @@ The parser is tolerant (unreadable bytes are skipped and counted, never fatal) a panics. `redact` and (later) `edit` build their interpreters on it; the graphics-state tracker and the `Patch` API of architecture §6 grow here. -Unfiltered inline images with built-in or Indexed colour spaces, and image masks, use their -sample layout (including per-row byte padding) to locate `EI`. This preserves pixel bytes -that look like the terminator. Filtered images and resource-defined colour spaces retain -the tolerant delimiter heuristic; damaged or truncated layouts fall back to it too. +An inline image ends where the renderer's tokenizer (`hayro-syntax`) ends it, so the parser +and the renderer read the same operators after the image, and redaction removes what the page +actually draws. Only where that tokenizer reads no image (its parameters don't read, or no `EI` +passes its checks) does the parser locate `EI` by its own rules: unfiltered images with built-in +or Indexed colour spaces, and image masks, by their sample layout (including per-row byte +padding), other images by the tolerant delimiter heuristic. Such an image is counted in +`Parsed::ambiguous_images`, because the operators after it may not be the ones the page draws. diff --git a/crates/redact/README.md b/crates/redact/README.md index 2caf067b5b..cca3d51fdc 100644 --- a/crates/redact/README.md +++ b/crates/redact/README.md @@ -20,7 +20,8 @@ clear_marks(&mut doc, None)?; // remove marks without app - **images**: fully covered → removed; partly covered → a copy with the covered pixels cleared (8/16-bit and 1/2/4-bit images, image masks; Flate/LZW/RL/A85/AHx). Codecs PdfCraft can't re-encode (DCT, JPX, JBIG2, CCITT) are removed whole (fail-closed); inline images under an - area are removed. Images with separate `/SMask` or `/Mask` data are removed whole; + area are removed. Images with separate `/SMask` or `/Mask` data, and images whose data decodes + to more than twice their declared raster (plus a byte per row and 4 KiB), are removed whole; cleared copies drop `/Alternates` so alternate pixels cannot survive; - **vectors**: covered paths are removed; partly covered paths and shadings are clipped so nothing paints inside the areas; @@ -31,8 +32,13 @@ clear_marks(&mut doc, None)?; // remove marks without app page as a `/PCMark /Redaction` stream. A verification pass re-reads each redacted page and fails the operation if any glyph or inline -image is still under an area. Content that can't be decoded makes the operation fail rather than -leave it unredacted. A Redact annotation with neither a usable `/QuadPoints` array nor a usable +image is still under an area. It checks every content stream the page had, whatever its +dictionary calls it; only the overlay streams this `apply` added (`Report::overlays`) are skipped. +Text is placed with the font and size set by `Tf` or by an ExtGState's `/Font` through `gs`, and a +form XObject starts from the text state of the content that draws it. Content that can't be +decoded makes the operation fail rather than leave it unredacted, and so does an inline image the +renderer's tokenizer reads no image for (`RedactError::Unreadable`): where the page's operators +resume after it would be a guess. A Redact annotation with neither a usable `/QuadPoints` array nor a usable `/Rect` makes it fail with `RedactError::UnreadableMark` before anything changes, instead of skipping that mark. The count covers the marks on the pages being applied. @@ -50,15 +56,19 @@ as Sanitize drops them, so a full rewrite of a tagged PDF can't keep a removed c A tree where that can't be done (an element written in place, or one too large to walk) makes `apply` fail with `RedactError::Tags` rather than leave the annotation reachable. -Replacement descriptions are removed only from marked-content spans changed by cleanup. -Unchanged spans retain their descriptions; unused property entries are retired during redaction +Replacement descriptions (`/Alt`, `/ActualText`, `/E`) are removed from marked-content spans +changed by cleanup, from every structure element above them (found through both `/P` and `/K`), +and from elements that lose an annotation reference, which also lose `/T`. An element written in +place above one whose descriptions go makes `apply` fail with `RedactError::Tags`. Unchanged +spans retain their descriptions; unused property entries are retired during redaction and hidden-content cleanup, including aliases in shared/inherited resources. Descriptions still used by surviving pages or forms are kept. A redacted page that inherits `/Resources` from the page tree gets them pinned (by reference; a direct inherited dictionary is made one shared object first) before it is rewritten. The parent's `/Resources` is then retired unless another page still inherits it, so it cannot keep a removed -XObject reachable. Pages that aren't redacted are left untouched. +XObject reachable. Surviving form XObjects lose the resource entries for removed XObjects their own +content doesn't draw, for the same reason. Pages that aren't redacted are left untouched. ## Remove hidden information / Sanitize