Merge pull request #7811 from dotCooCoo/fix/cmyk-images-from-pdf-or-eps-lose-their-source

PDF import: CMYK images keep the profile of their ICCBased color space

docs/target-app-parity.md

@@ -1909,6 +1909,7 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - The pixels of a PNG, JPEG, GIF or WebP file that Place decodes to check them are kept in the image store the renderers share, so the canvas's first frame with the placed image draws them without decoding the file again on the UI thread: File › Place, a file dropped on the canvas, a click or drag of the place cursor, `file.place`, and Paste of such an image. A CMYK JPEG is still decoded when it is first drawn (`crates/ui-egui/src/placing.rs`, `crates/render/src/tests.rs`).
   - A photo whose EXIF orientation turns or flips it (a camera held upright or upside down) is placed and opened upright, as it was taken; the image is stored as it is seen (#4284). A quarter turn swaps the resolution's axes, so the image keeps its physical size. TIFFs read without the image decoder (grayscale with extra channels, CCITT Group 3, CMYK with one plane per ink) follow their Orientation tag too, and a turned CMYK JPEG or TIFF keeps its inks, at the 8 or 16 bits the file has, as a CMYK TIFF.
   - PDF export writes a CMYK image that keeps its numbers in an `ICCBased` color space holding, byte for byte, the CMYK profile the image carries (a CMYK TIFF's tag 34675, or a CMYK JPEG's `ICC_PROFILE` APP2 segments) when `output.profiles` is `all` or `taggedSource`, and in PDF/A-2b, PDF/X-3 and PDF/X-4 unless it is `destination` ([the help page](https://helpx.adobe.com/illustrator/desktop/save-and-export/export-files-to-different-formats/pdf-marks-bleeds-and-color-output-options.html)). This covers a CMYK JPEG embedded as it is, one the Compression settings resample or compress again, a TIFF written again, and an image written with its mask as its soft mask. With `none`, and in PDF/X-1a, the image is DeviceCMYK and a JPEG's own profile is left out, so PDF/X-1a export writes a CMYK JPEG that carries a profile. Pixels the Output settings convert are never tagged with the profile of their old numbers. A profile tags an image only when its size, signature, class, CMYK color space and tag table are well formed and it is at most 16 MiB (VectorCraft's own limit). Transparency in a tagged CMYK document blends in the document's CMYK profile; when the file holds no space of that profile it blends in DeviceCMYK, or keeps its RGB space in PDF/A, and never in an image's own profile (`crates/pdf/src/tests/cmykimages.rs`, `export::writer::tests`).
+  - PDF import keeps the CMYK profile of an image in a four-component `ICCBased` color space, whose stream holds the profile ([ISO 32000-1, §8.6.5.5](https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf#page=157)), byte for byte with the image's ink amounts, so PDF export can write the image in it again. A CMYK TIFF carries it as tag 34675, whatever the image's Decode array and bit depth ([ICC.1:2010, Annex B](https://www.color.org/specification/ICC1v43_2010-12.pdf)). A CMYK JPEG kept as it is carries it in `ICC_PROFILE` APP2 segments in place of a profile of its own, with its compressed samples unchanged, and one whose segments can't hold it is stored as a CMYK TIFF carrying it. A profile that isn't well formed, isn't of CMYK colors or is over 16 MiB (VectorCraft's own limit) leaves the image's inks as they are, untagged. DeviceCMYK and DeviceN images carry no profile, and a CMYK TIFF's tag 34675 is read up to 16 MiB. EPS and PostScript import does not keep one: PostScript defines no `ICCBased` profile stream (`crates/pdf/src/tests/cmykimages.rs`, `cmyk::tests`).
   - An image that Open and Place store again keeps the ICC profile its file embeds and its 16-bit samples. A turned PNG, JPEG, WebP or TIFF stored as PNG, and a TIFF the image decoder reads, keep their gray or RGB samples at 8 or 16 bits with their gray or RGB profile in the PNG's `iCCP` chunk ([PNG specification, iCCP](https://www.w3.org/TR/png-3/#11iCCP)). A CMYK TIFF stored with one plane per ink and a turned CMYK JPEG or TIFF keep their CMYK profile as TIFF tag 34675, a JPEG's put together from all its APP2 segments ([ICC image-format guide](https://github.com/InternationalColorConsortium/iccDEV/blob/master/iccdev-mcp/docs/icc-format-guide.md)). A profile whose color space differs from the stored samples' is left out. The profile is kept in the stored image; how CMYK inks are drawn and exported to PDF does not change (`crates/engine/src/cmd/fileio/tests.rs`).
   - PDF export writes a stored gray or RGB TIFF in an `ICCBased` color space that holds the gray or RGB profile of its tag 34675, at 16 bits a sample from PDF 1.5 on and 8 before, with its alpha as a soft mask only when some pixel is not opaque ([ISO 32000-1, §8.6.5.5](https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf#page=157)). A gray or RGB image, a PNG included, that the Compression settings resample or compress with JPEG keeps its profile too, and gray pixels in an RGB profile stay RGB. Pixels the Output settings convert, a profile whose color space differs from the samples', and a malformed profile, a PNG's or JPEG's kept as it is included, are written without it; such a JPEG keeps its JPEG data. PDF/X-1a allows no ICC-based color spaces, so there a gray image with a gray profile, kept as it is, resampled or compressed with JPEG, is written in DeviceGray without the profile, a JPEG kept as JPEG with its JPEG data unchanged, and RGB images are converted to CMYK as before. CMYK images are unchanged (`crates/pdf/src/tests/compression.rs`).
   - PDF export with Output › Convert to Destination and an sRGB destination converts a gray or RGB image that carries an ICC profile from that profile to sRGB, with the color settings' rendering intent, and writes it without the profile, as the conversion applies to every color ([PDF options](https://helpx.adobe.com/illustrator/using/pdf-options.html)): 8-bit and 16-bit TIFFs (16 bits a sample from PDF 1.5 on when not resampled or recompressed), PNGs, JPEGs (kept as JPEG) and resampled images. A JPEG in an sRGB profile keeps its JPEG data, a black-and-white image whose converted levels are gray is written as grayscale, and without conversion every image keeps its profile. An image whose profile the color engine can't read, or whose pixels can't be decoded, is not converted: it keeps its profile, with a warning (`crates/pdf/src/tests/compression.rs`).