Merge pull request #7167 from dotCooCoo/fix/image-icc-16bit-kept

Images: an image stored again keeps its ICC profile and 16-bit samples

docs/target-app-parity.md

@@ -1670,7 +1670,8 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
   - On the desktop, File › Place reads and decodes files off the UI thread, one at a time, and places each once it is read, with "Placing" in the status bar and the busy spinner until then: the Place dialog's OK, a file dropped on the canvas, a click or drag of the place cursor, and the OK of the PDF, DXF and text import options. The files and thumbnails the place cursor is loaded with are read the same way, and the Place dialog's lines about its files are read on a thread of their own. Files are placed in the order they were started; a file is not placed while a dialog is open or a drag is under way, and a file whose document was closed meanwhile is not placed. `file.place` and `file.place.queue` over MCP and scripts reply as before.
   - On the desktop, Paste from a menu or shortcut captures another app's bitmap or reads a copied image file on the UI thread, then decodes the image on the file-reading worker. The status bar shows "Pasting" until the image is pasted. Windows device-independent bitmaps and Linux clipboard images are encoded as PNG on that worker. A Copy or Cut made while the image is read keeps its internal clipboard. `edit.paste*` over MCP and scripts reads the bitmap at once.
   - 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, 8 bits each, as a CMYK TIFF.
+  - 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.
+  - 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`).
   - SVG import shows a raster `<image>` whose EXIF orientation or TIFF Orientation tag turns or flips it upright, linked or as a data URL, and inside an SVG shown as an image: the pixels are stored turned, the width and height swap, and the `<image>` box fits the turned image under `preserveAspectRatio`, as CSS `image-orientation: from-image` describes (<https://www.w3.org/TR/css-images-3/#the-image-orientation>). A turned CMYK JPEG or TIFF keeps its inks as a CMYK TIFF, as does a CMYK TIFF that is not turned. TIFF data URLs (`image/tiff`, or untyped TIFF bytes) are read, and TIFFs with an alpha or other extra channel, CCITT Group 3 TIFFs and CMYK TIFFs stored one plane per ink are read as Open and Place read them. The pixels are decoded within the decode allowance, and a TIFF claiming more strips or tiles than the decoder can count is refused before it is decoded (`crates/svg/tests/it/image_orientation.rs`).
   - File › Place and a file dropped on the canvas refuse a PNG, JPEG, GIF or WebP file whose pixels can't be read, such as one cut short by a download or a sync still running, and the status bar shows "Couldn't place <name>: the image's pixels can't be read". Paste and Relink refuse such an image too, and Update Links, or Open when it reads the file again, counts it as missing. A JPEG cut short still places when its pixels can be decoded (`file.place`, `crates/engine/src/tests_place.rs`).
   - On the desktop, Copy and Cut make the system clipboard's formats (text, SVG, PDF, PNG) from a copy of the clipboard on the thread that writes background saves and exports, and write them when they are ready; while that thread has a save, an export, a print or a recovery copy to finish, they are made and written at once. Until they are written, Paste in VectorCraft takes the internal clipboard, and while a text field or the Type tool has the keyboard the app waits for them. Another Copy or Cut, or a copy of text in VectorCraft, drops them.