1-bit TIFFs compressed with CCITT Group 3 did not open, place or
relink: the image decoder reads Group 4 only and refuses Compression 2
(modified Huffman) and Compression 3 (ITU-T T.4).
They are now decoded with hayro-ccitt, the CCITT decoder that EPS
import uses. Compression 2 rows start at a byte and have no EOL codes.
Compression 3 rows follow an EOL code and are one-dimensional, or, with
T4Options bit 0, one- or two-dimensional as each row's tag bit says.
Fill bits, FillOrder 2, either PhotometricInterpretation, strips and
tiles are read.
A file whose pixels would take more than the decoding allowance as
RGBA is refused as too large to draw. A strip or tile whose data ends
before its last row is refused as damaged, and so is a tile larger
than the allowance. The strips and tiles together are read from at
most as many bytes as the file holds.
Part of #1466.
Docs: docs/file-format-parity.md, docs/target-app-parity.md.
In a CMYK document, an RGB color from the Eyedropper, a hex value or
paint.setFill was stored as CMYK by the profile-free formula
(k = 1 - max(r, g, b)), not through the color settings. RGB 83/170/223
came in as C63 M24 Y0 K13. A CMYK image was sampled through the RGB its
decoder shows, so its inks came back only when the formula happened to
round-trip them.
paint_from now converts an RGB color into a CMYK document with
Cms::convert and the settings' intent, as Document Color Mode and Swatch
Options already do. This covers paint.setFill and paint.setStroke,
gradient stops, swatch.new {color} and the Eyedropper. With Generic CMYK,
83/170/223 now separates to C59 M12 Y3 K0, and #ff0000 now separates to
C0 M97 Y100 K0 instead of C0 M100 Y100 K0. keepModel: true still keeps
RGB. paint.sampleColor with a stop stores the color the same way.
The Eyedropper samples a CMYK image's ink amounts (a four-component
JPEG, or an 8- or 16-bit chunky CMYK TIFF) and returns them unchanged
(ImageBlob::sample_cmyk_object), also in an RGB document. It takes an
RGB image's sRGB pixel into the working RGB space, as the screen color
sampler does, so the picked color shows as the pixel when the working
space is not sRGB.
Docs: docs/mcp.md, docs/target-app-parity.md.
TIFFs that store each channel as its own plane (PlanarConfiguration 2)
did not open, place or relink when they were CMYK or grayscale with
extra channels: the image decoder refuses planar CMYK, and the readers
for CMYK inks and for extra samples returned nothing for planar files.
The two readers now read every plane through the tiff crate and put
each pixel's samples together. A planar CMYK TIFF keeps its ink
amounts and is stored as a CMYK TIFF with each pixel's inks together,
at the file's resolution. Grayscale TIFFs with an alpha channel or
other extra channels, and CMYK TIFFs with alpha, read as their chunky
versions do.
A TIFF whose header claims more strips or tiles than the tiff decoder
can count is refused as too large to draw. The decoder multiplies
those counts without a check, which panics in builds with overflow
checks.
Part of #1466.
Docs: docs/file-format-parity.md, docs/target-app-parity.md.
File > Place, Relink and Open refused a grayscale TIFF whose pixels carry an alpha channel or
another extra channel: the image decoder reads neither. They are now read like CMYK TIFFs with
alpha: the first extra sample is the transparency when the file says it is alpha (associated alpha
divided back out), and other channels are left out.
The image decoder can't read a CMYK TIFF with an alpha channel at all
("color type Unknown(0)"); it is now read with the tiff crate, associated
alpha divided back out and the inks converted in the active colour settings.
And a 60 in sheet at 300 ppi (18000 x 6600 px) hit the decoder's 512 MB
default allocation limit; up to 2 GB is now allowed.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
A PDF's DeviceCMYK image opened as RGB (the interpreter's pixels as a PNG),
so every export wrote it as DeviceRGB or ICC RGB, silently. Images now keep
their CMYK samples, as CMYK colours already did:
- Model: CMYK images are blobs holding CMYK samples, a four-component JPEG
(Adobe's inverted samples) or a Deflate CMYK TIFF. vectorcraft-doc's cmyk
module reads their ink amounts (ImageBlob::is_cmyk, ::cmyk, capped at 64
megapixels) and writes the TIFF (ImageBlob::cmyk_tiff).
- PDF import: DeviceCMYK, CalCMYK and four-component ICC images keep their
samples. A JPEG with Decode [1 0 1 0 1 0 1 0] is kept byte for byte; any
other is decoded (8 or 16 bits, its Decode array applied) and stored as a
CMYK TIFF. Masked CMYK images and 1/2/4-bit ones open in RGB with a warning.
Placing a CMYK TIFF keeps it CMYK too.
- PDF export: CMYK images are written in CMYK (DeviceCMYK, or ICC-based with
the CMYK profile when colours are tagged: PDF/X-3, PDF/X-4, PDF/A). A CMYK
JPEG neither resampled nor recompressed passes through unchanged; others are
resampled in CMYK and compressed as ZIP or as a CMYK JPEG (jpeg-encoder,
which also replaces the ZIP fallback and its warning for images converted to
CMYK). Output conversion treats them like CMYK colours: Preserve Numbers and
PDF/X-1a keep their numbers, Convert to Destination converts them to another
CMYK profile or to RGB through a 17^4 lookup table (cms::CmykLut, now also
behind the renderer's ink table). A CMYK image that can't be decoded is
reported in the warnings.
- Canvas: CMYK images show through the working CMYK profile, as CMYK fills
do, and paint their own inks in ink planes (CMYK raster exports, CMYK
blending). SVG export writes TIFF images as PNG.
Illustrator's Output › No Conversion keeps colour data as it is
(https://helpx.adobe.com/illustrator/using/pdf-options.html).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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