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Average filter: transparency reference
The Average filter replaces colour while retaining each pixel's transparency. Two synthetic cases were executed in Photoshop 26.6.1 on Windows x64 on 2026-10-23. These are observations of RGB8 raster layers, without a selection or transparency lock; they are not a claim of parity in other colour modes or at other bit depths.
Each input is a 16 × 16 RGBA PNG. Its left eight columns are red and its right eight columns are blue. Open it in Photoshop, run Filter › Blur › Average, and save a PNG copy. Inspect the file's RGBA values, including invisible colours.
| Input left / right RGBA | Output left / right RGBA |
|---|---|
(255,0,0,255) / (0,0,255,0) |
(128,0,128,255) / (128,0,128,0) |
(255,0,0,64) / (0,0,255,192) |
(128,0,128,64) / (128,0,128,192) |
An opaque control produces (128,0,128,255) throughout. Thus transparency is
neither a weight in this colour average nor a channel to replace with its mean.
PhotoCraft previously alpha-weighted the RGB mean and replaced alpha with its mean. On the first case that predicts translucent red throughout, rather than purple pixels with their original transparency. The fix uses selection coverage for the existing mean and leaves each pixel's alpha alone. Selection mixing and the existing colour conversion path are unchanged. In particular, this does not establish Photoshop parity for feathered selection weighting or CMYK/Lab means.
The engine tests construct their own pixels; no Photoshop binary, proprietary code, or reference image is included. They cover transparent and partially transparent pixels, selection boundaries, one history step, undo and redo at 8/16/32-bit storage. The higher-depth tests establish PhotoCraft invariants; the external reference measurements above are RGB8 only.
Run the focused regressions with:
cargo test -p photocraft-engine --lib average_preserves
Smart filters
The PSD importer already recognizes the optionless Avrg descriptor (see
#6297). Recognition alone did
not execute it: the shared renderer returned None, leaving the source pixels
unchanged, and the raster-only command was disabled on Smart Objects.
Average now uses the shared filter command and algorithm. It can be added to a Smart Object, toggled, undone and redone, or re-rendered from an imported record. The raster path retains its canvas limit, selection weighting and alpha behavior. Like other core filters, new invocations validate parameters before editing.
The integration tests create their own red/blue Smart Objects at RGB8/16/32f. They check the dispatcher, command enablement, one history step, visibility, undo/redo, and re-rendering after clearing both the layer and stage caches:
cargo test -p photocraft-engine --test it average_smart
An additional, explicitly ignored test accepts a local Photoshop oracle. To
reproduce it in Photoshop, create an opaque 16 × 16 RGB8 image with eight red
columns followed by eight blue columns, convert the layer to a Smart Object,
apply Average and save a PSD. Photoshop 26.6.1 on Windows produces purple
(128,0,128,255) throughout. Then run, in PowerShell:
$env:PHOTOCRAFT_AVERAGE_PSD = 'C:\path\to\average-smart.psd'
cargo test -p photocraft-engine --test it average_photoshop_psd_rerenders_from_source -- --ignored --nocapture
This test discards the imported layer cache and the smart-filter stage cache, then rebuilds from the embedded source. Merely importing or flattening the PSD would reuse Photoshop's saved pixels and would not prove execution. The local PSD is not committed and the opt-in test does not raise a corpus floor.