TIFF: planar grayscale files with extra channels, and planar CMYK files, open and place

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.

docs/file-format-parity.md

@@ -101,6 +101,7 @@ the app's own editing copy of a file (an EPS after its `%%EOF`, a `.ai`'s `AIPri
 | EMF / WMF | open, export | yes | yes | an oversized embedded PNG or JPEG is refused from its header, before any pixels are decoded (#1776) |
 | PSD | open, place, export | yes (merged image, every mode and depth) | yes (layered, max editability) | placing as layers (Photoshop Import Options) missing; the embedded ICC profile's tags are 4-byte aligned (#1584) |
 | PSB | open | yes (merged image) | no | |
+| PNG / JPEG / GIF / BMP / TIFF / Targa | open, export | yes (Targa: export only) | yes; TIFF is also selectable in Export for Screens and Asset Export with its existing options | Targa import missing; TIFF: grayscale with an alpha channel or other extra channels reads (#1466 in part), and so do files that store each channel as its own plane (PlanarConfiguration 2), CMYK ones with their ink amounts; CCITT Group 3 doesn't; the ICC profiles embedded in JPEG and TIFF have 4-byte aligned tags (#1584) |
 | PNG / JPEG / GIF / BMP / TIFF / Targa | open, export | yes (Targa: export only) | yes; TIFF is also selectable in Export for Screens and Asset Export with its existing options | Targa import missing; TIFF: grayscale with an alpha channel or other extra channels reads (#1466 in part), CCITT Group 3 and planar files with extra channels don't; the ICC profiles embedded in JPEG and TIFF have 4-byte aligned tags (#1584); PNG export marks its colours as sRGB (`embedIcc`, an `sRGB` chunk; no ICC profile is embedded, #2221) |
 | WebP | export (Export for Screens) | yes | yes (lossless only; lossy written lossless with a warning) | |
 | HEIC / HEIF | open, place | no | no | |

docs/target-app-parity.md

@@ -617,7 +617,8 @@ Moved from the ROADMAP's "Shipped so far" on 2026-10-10. Update it when a featur
     A PDF page whose `UserUnit` (PDF 1.6) is above 1 opens at its size in points, its numbers times the `UserUnit` (one above 75,000 counts as 75,000), and `document.pdfInfo` gives its size and boxes in points too. A `.ai` whose editing data has its artboards in the units of such a page opens from that data at the page's size, with its layers, and when the layers can't be read its pages still take the artboard layout of the data, scaled the same way (part of #1482).
     PDF export and `.ai` saves write a page with a side longer than 14,400 pt with a `UserUnit` (PDF 1.6), its longer side divided by 14,400 and rounded up to the next thousandth, so that no side is longer than 14,400 units (ISO 32000-1, Annex C.2); in PDF 1.3 to 1.5 files and PDF/X files such a page is written in points.
     Placed (linked) files in a `.ai`'s editing data come in as linked images in their place, each showing the low-resolution preview the file keeps of it until its file is found or relinked in the Links panel (a file found next to the document or at its path is read as the document opens). A file with them no longer falls back to its PDF part, so its guides, sublayers and hidden objects open (#1264; `crates/eps/src/import/ai/tests.rs`, `crates/engine/src/tests_links.rs`). In a file opened that way, a gradient with stops in the middle runs its whole ramp across its shape and a gradient object no longer passes its fill to the next path (#1390); text objects with an appearance keep their own text and frame, type of hidden layers stays hidden, and type on later artboards lands on its text objects (#1391); area type whose frame is too short for a line of the fallback font shows its first line, the frame made taller with a warning in the open result (#1392).
-  - EPS and DXF in and out, EMF/WMF in and out; PNG (with PNG-8), JPEG, WebP, GIF, TIFF, BMP, Targa and layered PSD export; grayscale TIFFs with an alpha channel or other extra channels place, relink and open, the alpha as the image's transparency (#1466 in part; CCITT Group 3 and planar files with extra channels are not read); PSD and PSB files open and place, linked or embedded, as their merged image in every colour mode and depth (#918). EPS import runs a PostScript Level 3 interpreter written from the PostScript Language Reference: resource categories and `resourceforall`, local and global VM (`currentglobal`/`setglobal`/`gcheck`), `clipsave`/`cliprestore`, subarrays and substrings that share storage, the standard dictionaries in `systemdict`, `dictstack`, `internaldict`, executable filters and strings, `load` by any key, `//name` immediate names, `token`, `execform`, user paths, `cshow`, `rootfont`, `cachestatus`, colour rendering and halftone queries, file `status` and data read with `flushfile`, and `pdfmark` marks dropped (Discord feedback, #466, #469, #474). Masked images (`ImageType 3` in its three interleavings) and reusable streams are read, and an image's several data sources are read in turn, as the reference defines (procedures that read one file get their own rows: such images came in banded, #498). `restore` puts dictionaries back as they were at the `save`, so programs that count their saves in a dictionary read to their end (part of #505). Tiling patterns come in as pattern swatches, uncoloured ones too; Type 3 fonts' glyphs as their outlines, spaced by `ashow`/`widthshow`/`xshow`/`kshow`; mesh and function-based shadings (types 1, 4–7) as gradient meshes; sampled functions (type 0) and Flate/LZW predictors are read. It is tested with programs written from the specification in the ways common generators use these features; Inkscape/cairo EPS files open as vectors. When a file's PostScript still can't be read, it opens as its TIFF preview, its Windows metafile preview (as vectors) or its EPSI preview, and the warning (in the status bar, `document.open`/`app.open`/MCP `open_file` replies and `vectorcraft-cli info`) names the error, the operator that raised it and the procedures it ran in. Legacy PostScript `.ai` files (Illustrator 3–8, written with the prolog that defines their operators) keep their groups and nested groups (`u` … `U`), between and inside clipping groups; EPS and EMF/WMF import nest clips (and groups) at most 128 deep, so a hostile file can't exhaust the stack. DXF TEXT justified Fit or Aligned spans its two points (stretched, or scaled as a whole). PDF export writes type as real, searchable text in embedded subset fonts by default, as Illustrator's PDF presets do (Convert Text to Outlines is an option; printer's marks stay shapes), so text-heavy PDFs stay small (#733). DXF export writes each fill as its outlines followed by its hatch, so laser and cutter software, which skips hatches, gets filled art and type too (#546).
+  - EPS and DXF in and out, EMF/WMF in and out; PNG (with PNG-8), JPEG, WebP, GIF, TIFF, BMP, Targa and layered PSD export; grayscale TIFFs with an alpha channel or other extra channels place, relink and open, the alpha as the image's transparency (#1466 in part; CCITT Group 3 files are not read); PSD and PSB files open and place, linked or embedded, as their merged image in every colour mode and depth (#918). EPS import runs a PostScript Level 3 interpreter written from the PostScript Language Reference: resource categories and `resourceforall`, local and global VM (`currentglobal`/`setglobal`/`gcheck`), `clipsave`/`cliprestore`, subarrays and substrings that share storage, the standard dictionaries in `systemdict`, `dictstack`, `internaldict`, executable filters and strings, `load` by any key, `//name` immediate names, `token`, `execform`, user paths, `cshow`, `rootfont`, `cachestatus`, colour rendering and halftone queries, file `status` and data read with `flushfile`, and `pdfmark` marks dropped (Discord feedback, #466, #469, #474). Masked images (`ImageType 3` in its three interleavings) and reusable streams are read, and an image's several data sources are read in turn, as the reference defines (procedures that read one file get their own rows: such images came in banded, #498). `restore` puts dictionaries back as they were at the `save`, so programs that count their saves in a dictionary read to their end (part of #505). Tiling patterns come in as pattern swatches, uncoloured ones too; Type 3 fonts' glyphs as their outlines, spaced by `ashow`/`widthshow`/`xshow`/`kshow`; mesh and function-based shadings (types 1, 4–7) as gradient meshes; sampled functions (type 0) and Flate/LZW predictors are read. It is tested with programs written from the specification in the ways common generators use these features; Inkscape/cairo EPS files open as vectors. When a file's PostScript still can't be read, it opens as its TIFF preview, its Windows metafile preview (as vectors) or its EPSI preview, and the warning (in the status bar, `document.open`/`app.open`/MCP `open_file` replies and `vectorcraft-cli info`) names the error, the operator that raised it and the procedures it ran in. Legacy PostScript `.ai` files (Illustrator 3–8, written with the prolog that defines their operators) keep their groups and nested groups (`u` … `U`), between and inside clipping groups; EPS and EMF/WMF import nest clips (and groups) at most 128 deep, so a hostile file can't exhaust the stack. DXF TEXT justified Fit or Aligned spans its two points (stretched, or scaled as a whole). PDF export writes type as real, searchable text in embedded subset fonts by default, as Illustrator's PDF presets do (Convert Text to Outlines is an option; printer's marks stay shapes), so text-heavy PDFs stay small (#733). DXF export writes each fill as its outlines followed by its hatch, so laser and cutter software, which skips hatches, gets filled art and type too (#546).
+  - TIFFs that store each channel as its own plane (PlanarConfiguration 2) place, relink and open as the same image stored pixel by pixel does, 8 and 16 bits: grayscale with an alpha channel or other extra channels, and CMYK with or without them. 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. A TIFF whose header claims more strips or tiles than can be counted is refused as too large to draw (#1466 in part; `crates/engine/src/cmd/fileio/tests.rs`).
   - EPS and PostScript import keeps a CMYK image's ink amounts, as PDF import does: the samples of `image` and `colorimage` in a CMYK color space, and of a CMYK JPEG read through `DCTDecode`, come in as a CMYK TIFF, read through the image's Decode array, and the pixels a `MaskColor` or `ImageType 3` mask hides become a grayscale opacity mask (`crates/eps/src/import/tests_images.rs`). Such images came in as RGB PNGs.
   - DXF control-point SPLINE import honors its closed flag (#1299 follow-up after #1320 fixed export), including rational curves; open curves whose endpoints meet stay open. Own-fixture regressions cover controls/knots, fit-point fallback and all export versions (`crates/cad/src/import/tests.rs`, `crates/cad/src/tests.rs`); native save/read checked; CIRCLE/ARC fitting, CNC preset and VCarve QA remain pending.
   - Affinity documents in (AF.1–AF.4): `.af` (Affinity 3) and `.afdesign`/`.afphoto`/`.afpub` (Affinity 1 and 2, container versions 8–12) open and place as editable art: layers and sublayers, groups (pass-through or isolated), artboards (with their names and backgrounds) and Publisher pages side by side, curves with live corners, parametric shapes (rectangles with corner radii, ellipses, polygons, stars, pies, triangles, trapezoids), compound shapes, solid/linear/elliptical gradient fills and strokes (weight, dashes, alignment, scale-with-object), clipping by nesting, vector and pixel masks, artistic and frame text with fonts, sizes, tracking, leading and alignment, placed images (their original JPEG/PNG) and pixel layers (8/16-bit RGB, CMYK), opacity, visibility, locking and blend modes, at the document's resolution in points. Effects, adjustments, brushes and pressure profiles, transparency gradients, master pages, symbol instances (imported as their cached picture), special shapes (cloud, heart, cog…, imported as ellipses) and Affinity-only blend modes are named in the import warning. A file whose native data can't be read opens as its embedded preview with the reason, and that preview can't be placed. Save never writes back over the Affinity file and there is no Affinity export. AF.4 adds Affinity 3 artboard recognition and actual-outline clipping, source-backed JPEG/PNG raster tiles, Unicode text-run recovery, stored fallback/exact installed fonts, OpenType feature flags and compound-geometry limits. 51 public CC0/MIT/Apache-2.0 files (33 current `.af`), pinned and sha256-verified (`cargo xtask corpus --affinity`), test native retention and every-board native/SVG/PDF/PSD output for current files; selected files compare their saved thumbnails. No Affinity reopen or independent paired PSD oracle was available; [source audit and complex-font gaps](affinity-validation.md); [scope, provenance and limits](../crates/affinity/README.md).