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…#113) Swaps the WCSLIB-backed **WCS.jl** dependency for the pure-Julia [**FITSWCS.jl**](https://github.com/JuliaAstro/FITSWCS.jl) for all World Coordinate System parsing and pixel↔world transforms. This removes the C/binary WCSLIB dependency and lets WCS be parsed directly from the FITS header (no header --> string round-trip). ### Changes #### Core - `emptywcs`: `WCSTransform(n)` --> `WCS(n)`. - `wcsfromheader`: parses the `FITSHeader` directly via FITSWCS's FITSIO extension instead of serializing to a string. - `pix_to_world` / `world_to_pix` / `world_to_pix!` now call FITSWCS's `pixel_to_world` / `world_to_pixel`. The 1-based `CRPIX` convention and column-per-coordinate batch layout are identical, so the internal offset arithmetic is unchanged. - These functions are now owned/exported by AstroImages rather than re-exported from WCS.jl. **Public API names are preserved.** - Widened `AstroImage` constructor signatures to `AbstractVector{<:WCSTransform}` and added a normalizing constructor, since FITSWCS's `WCSTransform{N, ...}` is parametric (a concrete `Vector{WCSTransform{2, ...}}` is _not_ `<: Vector{WCSTransform}` under Julia's invariance). - Removed dead code (`serializeheader` / `hdrval_repr`), previously only used to feed `WCS.from_header`. - WCS coordinate systems are now identified by their **version character** (`' '` for the primary system, `'A'`–`'Z'` for alternates), matching the FITS standard and astropy's `WCS(header, key=...)` replacing the previous integer index. | Before | After | | --------------- | ----------------- | | `wcs(img, 1)` | `wcs(img, ' ')` | | `wcsn = 1` | `wcsn = ' '` | | `wcsn = 2` | `wcsn = 'A'` | - **Multiple alternate WCS** are parsed via upstream [`FITSWCS.WCS_all`](JuliaAstro/FITSWCS.jl#14) - `wcs(img)` now returns a `Dict{Char,WCSTransform}` (was `Vector{WCSTransform}`), so `keys(wcs(img))` enumerates the systems present. #### Docs - Removed the WCS.jl InterLinks entry; `pix_to_world` / `world_to_pix` are now documented in the AstroImages `@docs` block (added a docstring for `world_to_pix`). - Updated prose references (WCS.jl --> FITSWCS.jl). #### Tests - `test/general.jl` multi-WCS test is now self-contained: asserts system count + `ctype` and a pixel→world→pixel round-trip. - `test/plots.jl`: `WCSTransform(2; ...)` --> `WCS(2; ...)`. #### Dependencies | Change | Details | | --- | --- | | ➖ Removed | `WCS` from package / test / docs `Project.toml` | | ➕ Added | `FITSWCS` (via `[sources]` --> GitHub repo until registered) | | ⬆️ Version | `0.5.1` --> **`0.6.0`** | > [!NOTE] > WCS.jl still appears transitively via `Reproject.jl` in the **docs** environment only. It is no longer a direct dependency of AstroImages, the test env, or the docs env. ### Compatibility - Public API (`wcs`, `pix_to_world`, `world_to_pix`, `world_to_pix!`, `WCSTransform`) is unchanged. - `wcs(img)` now returns FITSWCS `WCSTransform` objects. Field access used by AstroImages (`.naxis`, `.ctype`, `.cunit`, `.crval`, `.radesys`) is preserved. > [!WARNING] > WCS.jl-specific helpers (`to_header`, `from_header`, `WCS.HDR_ALL`) are no longer available, and the `WCSTransform` type itself changes, hence the minor (`0.6.0`) version bump.
Closes the loop on the `slice_wcs` integration discussed in #113 (comment). Depends on JuliaAstro/FITSWCS.jl#17. ## Motivation This PR aims to adopt `FITSWCS.slice_wcs` to simplify the parent-frame bookkeeping here, and also fix several correctness bugs that were unearthed in the process. ## Bugs fixed 1. **Strided slices off by `step-1`**: Legacy mapped slice-local --> parent as `p*step + first - 1`. Correct is `(p-1)*step + first`. The formulas agree only when `step == 1`, so `img[1:2:9, :]` reported world coordinates one parent pixel off. 1. **Frozen refdims off by one pixel**: Dropped axes were fed `dim[1] - 1`. `pixel_to_world(slice; all = true)` reported, e.g., `FREQ = 1.0e9` where the truth for a slice at parent index 2 is `1.001e9`. (Also affected the slice-label values in `implot` titles.) 1. **`parent = true` shifted by one pixel**: `pixel_to_world(img, p; parent = true)` equaled `raw(p .- 1)`, disagreeing with the default path on an unsliced image and shifting WCS-grid extents in the plot recipes by one pixel. 1. **Coupled inverses were garbage**: `world_to_pixel` stuffed frozen *pixel indices* into *world* coordinate slots before inverting. Harmless only when axes are fully separable. Frozen axes now contribute their exact world values (one forward evaluation). 1. **Underdetermined inverses were silent**: Slicing one axis of a celestial lon/lat pair leaves world axes that depend on the dropped pixel axis. `world_to_pixel` now throws a descriptive `ArgumentError` (astropy's `SlicedLowLevelWCS` similarly refuses) instead of returning wrong pixels. 1. **`wcsdims` lost on every slice**: Both `rebuild` methods defaulted to recomputing `wcsdims` from the already-sliced dims (DimensionalData no longer routes slicing through `rebuildsliced`), which broke categorical (Stokes) refdim resolution *and* name-tracked transposition. `rebuild` now preserves the parent `wcsdims`. ## New architecture (`src/wcs.jl`) - `pixel_to_world`: one body for all cases. Expand dims-ordered coords into the full parent frame (kept dims via their lookups, frozen refdims at their parent positions, degenerate header axes at CRPIX), evaluate the full transform, filter to the selected dims (`all = true` returns every axis). - `world_to_pixel` (default): Delegates to a `SlicedWCSTransform` (`FITSWCS.slice_wcs`) describing the current view, guarded by `world_keep == pixel_keep`. - `world_to_pixel(parent = true)`: Unchanged contract for the WCS-grid plot recipes (`naxis` coordinates, WCS axis order), now with exact frozen-axis world values. - Both legacy scatter/gather bodies and the `_world_to_pixel` worker are deleted. Docstrings now document `wcsn` / `all` / `parent` and the 1-based FITS convention. ##⚠️ Breaking / behavior changes - **`world_to_pixel(img, ...)` returns `ndims(img)` slice-local coordinates** in `dims(img)` order (was: `naxis` parent-frame values), making it the actual inverse of `pixel_to_world`. Parent-frame output remains available via `parent = true`. - **`world_to_pixel` throws** on slices that drop a pixel axis the remaining world axes depend on (was: silently wrong values). - **`parent = true` no longer shifted by one pixel**. WCS grid overlays now land at their true positions. - Strided-slice and frozen-axis coordinates corrected per bugs 1–2 above.
…120) **Before:** ```julia-repl julia> img["KEY"] = nothing ERROR: MethodError: no method matching FITSFiles.Card(::String, ::Nothing) The type `FITSFiles.Card` exists, but no method is defined for this combination of argument types when trying to construct it. Closest candidates are: FITSFiles.Card(::Any, ::Any, ::Any, ::Any, ::Any) @ FITSFiles ~/.julia/packages/FITSFiles/0MEHx/src/card.jl:232 FITSFiles.Card(::S; ...) where S<:AbstractString @ FITSFiles ~/.julia/packages/FITSFiles/0MEHx/src/card.jl:237 FITSFiles.Card(::S, ::V; ...) where {S<:AbstractString, V<:Union{Missing, AbstractString, Number}} @ FITSFiles ~/.julia/packages/FITSFiles/0MEHx/src/card.jl:237 ... ``` **After:** ```julia-repl julia> img["KEY"] = nothing ```
Now we can do `img = load(myfile.fits; scale = false)` to read the data as exactly stored on disk
… on any header write (#126) `setindex!` on an `AstroImage` header key previously consulted a ~250-line `WCS_HEADERS_TEMPLATES` table (expanded into an exact-match `Set`) to decide whether to mark the cached `WCSTransform` stale. Such a filter can't be complete. WCS keywords span Papers I–IV plus legacy conventions, with unbounded axis indices and `A`–`Z` alternate-system suffixes, and the table had real holes: the expansion only covered axis indices 1–4 and lowercase alternate suffixes, so e.g. `img["CRPIX5"] = 3.0` or `img["CRPIX1A"] = 3.0` silently left a stale transform in use. Now any header write marks the cached WCS stale, and it is lazily re-parsed on the next `wcs()` access. Re-parsing is cheap and header writes are rare, so the extra invalidations cost effectively nothing, while false negatives are gone by construction. The staleness regression test now covers the previously-missed key classes. Breaking only in the internal sense: the unexported `WCS_HEADERS_TEMPLATES`/`WCS_HEADERS` constants are gone, and cache invalidation is now unconditional rather than keyword-filtered.
icweaver
marked this pull request as draft
July 29, 2026 20:55
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icweaver
added this pull request to stack #142
October 2, 2026 19:59
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WIP