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#260 (page 7) compares PdfCraft with Acrobat, which draws an Ink annotation's /InkList as a smooth curve through the points; pdfcraft-annot drew straight segments between them (as MuPDF, Poppler and PDFium do). A stroke of three or more points is now drawn as a Catmull-Rom spline through every point, written as cubic Béziers: the curve leaves each point parallel to the chord between its neighbours, and an end uses itself as the missing neighbour. Two points stay a line and one point a dot. This is the appearance PdfCraft writes for its own ink, signatures drawn with Fill & Sign included, and, with the display-only appearances for comments that have none, how ink without /AP is shown. A curve can swing beyond its points, so a new ink annotation's /Rect now also covers the curve's control points (the curve stays within them); before, only the points plus the line-width margin. Test: annot tests::ink_strokes_are_smooth_curves_through_their_points checks the exact curve for a three-point stroke, a line for two points, a dot for one, and a /Rect that holds a stroke whose curve rises above its highest point (22 on main, 23.667 now). The comment.pencil parity entry cites it. Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com> Co-authored-by: Brandon Thomas <echelon@gmail.com>
pdfcraft-annot
Comments (annotations), ISO 32000-2 §12.5. Layer L3, depends only on pdfcraft-cos.
What it does
- Builders for the comment types Acrobat's commenting tools create: sticky note (
Text+Popup), highlight, underline, strikethrough, squiggly, rectangle (Square), oval (Circle), line and arrow (Linewith/LE), freehand drawing (Ink) and text box (FreeText). - Appearance streams (
appearance::build) generated from the annotation dictionary, so new and restyled comments look the same in every viewer. Highlights multiply (/BM /Multiply). Note icons are PdfCraft's own drawings. Text boxes use standard Helvetica (WinAnsi), with line breaking by approximate Helvetica proportions (no font program is bundled). - Edits: reply (
/IRT), set review status (a/Statereply, as Acrobat's "Set status" does), change text, move, resize, restyle, delete (with pop-up and replies).
API sketch
let index = add_annotation(&mut doc, &NewAnnotation { page, shape, style, contents, author }, &meta)?;
add_reply(&mut doc, page, index, "Agreed", "Ada", &meta)?;
set_review_state(&mut doc, page, index, ReviewState::Accepted, "Ada", &meta)?;
move_annotation(&mut doc, page, index, dx, dy, &meta)?;
set_style(&mut doc, page, index, Some(rgb), Some(0.5), Some(2.0), &meta)?;
delete_annotation(&mut doc, page, index)?;
signature_image(&doc, page, index)?; // embedded image XObject of Fill & Sign signature/initials
A comment is addressed by (page, index in /Annots), the same pair
pdfcraft_render::Annotation reports. Meta carries the date and the /NM id so edits stay
deterministic; the engine supplies them.
Fidelity rules
- Unknown keys are kept. Inline annotation dictionaries are promoted to indirect objects only when an edit needs a reference to them.
set_stylerefuses (and changes nothing) when it cannot redraw the comment, e.g. stamps, cloudy borders or callouts, instead of leaving a stale appearance.- Replies get the parent's
/Rectand an empty appearance: they appear in comment lists but never paint a second icon. - Resizing a stamp changes its
/Rectand preserves its original appearance and resources; viewers scale that appearance into the new rectangle. Locked stamps refuse the edit.
Not yet
Callouts, polygons and polylines, clouds, carets (insert/replace text), stamps, file
attachments, rich text (/RC, /DS), and the shared named-appearance cache Acrobat writes.