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Grzegorz MartensandClaude Opus 5.5
a4058c9242
Redaction doesn't decode CCITT yet, so a mark over part of a picture Create PDF stored as Group 4 removes the whole picture (nothing leaks); before this PR such pictures were eight-bit Flate and had only the covered pixels cleared. The create README and the image-to-PDF parity note say so; #4384 adds CCITT to redaction. The workspace's comment on hayro-ccitt says Export uses it, not only tests. 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
40 lines
2.9 KiB
Markdown
40 lines
2.9 KiB
Markdown
# pdfcraft-create
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Layer L4. Create a PDF (Acrobat's Create a PDF tool), execution plan M10.2:
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- `blank(width, height, pages)`: an empty document;
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- `from_images(&[(name, bytes)])`: one page per image, sized from the image's resolution
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(PNG `pHYs`, JPEG JFIF density; 72 dpi when absent). JPEG data is embedded as is
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(`/DCTDecode`, grey, RGB or Adobe-inverted CMYK); PNG is decoded and stored with Flate,
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with transparency as a soft mask. A picture of only pure black and white (a 1-bit PNG or TIFF,
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eight-bit grey, a two-colour palette, RGB without a profile) is stored at one bit per pixel, as
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CCITT Group 4 or Flate, whichever is smaller as stored (`pdfcraft_filters::encode_g4`).
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Redaction doesn't decode Group 4 yet: a mark over part of such a picture removes the whole
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picture (nothing leaks). An ICC profile in the file (JPEG `APP2 ICC_PROFILE`, PNG
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`iCCP`) that matches the image's colour space is kept as an `/ICCBased` colour space with
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the device space as `/Alternate`; images with the same profile share one profile object.
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JPEG metadata scanning skips marker fill bytes and reads application segments after the
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frame header, stopping at the first scan or end marker. Broken or mismatched ICC profiles
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still fall back to the device colour space;
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- `from_images_with_resolution(images, ImageResolution::Dpi(dpi))`: override the page
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resolution (1–1200 dpi), without resampling or recompressing image pixels. Use 72 dpi
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for one point per pixel, or `ImageResolution::Embedded` for the same behavior as
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`from_images`. The largest page side is still capped at 14,400 points;
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- `from_text(text, …)`: plain text set in Helvetica, wrapped and paginated. Text Helvetica
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can't draw is refused, naming the line and the character, never set as `?`.
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- `from_text_escaped(text, …)`: the same for reports PdfCraft generates from documents
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(comment summaries, compare reports): such characters are written as `[U+XXXX]` and the first
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line says so (`ESCAPED_NOTE`).
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Every function returns a `pdfcraft_cos::Document`; the caller writes it.
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Image export and Save Image As apply each lossless image's Decode pair before converting its color components.
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Indexed Decode values select palette entries after rounding and clipping. Color-key masks compare the original samples.
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Missing, null or malformed Decode arrays keep the default mapping.
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Soft-mask Decode intervals map samples to opacity before the mask is resized, including reversed ranges and indirect entries.
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The existing 16-bit path still uses each sample's high byte.
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JPEG image Decode handling remains limited.
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ICC transforms and calibrated color conversion remain outside this export path.
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CCITT fax images (Group 3 and 4) are decoded for export through `hayro-ccitt` with their `/DecodeParms`
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(`/Columns` has to be the image's width), behind other filters such as `ASCII85Decode` too; JPEG 2000 and JBIG2 images are still reported, not exported.
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