layer_stack — GFX2D `composite` op

• Data kinds: table → rgba

• Call: import gfx2d; gfx2d.layer_stack(layers) (or opsgfx2d.get("layer_stack"))

Usage

Composite a z-ordered list of `rgba` layers, bottom first.

Each layer is a dict:

`{"image": rgba, "mode": str = "normal", "opacity": float = 1.0}`

and the W3C rule for a blend mode against a *partially transparent* backdrop

is used — the blend function is weighted by the backdrop's own alpha,

`Cs' = (1 - a_b) Cs + a_b B(Cb, Cs)` — so a layer over empty space keeps

its own colour whatever the mode. The result is straight-alpha `rgba`.

All layers must share one shape; see :func:alpha_composite on why.

Raises ValueError: empty list, more than :data:MAX_LAYERS, a non-dict

entry, an unknown key, mismatched shapes.

References (sample data, literature)

• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).

• Operator provenance and references — the sources of the research/methods this op family came from.

• The canonical algorithm (author, year) and its uses are named in the family usage guide above.

Runnable examples (verified samples that actually call this op)

• gfx2d_scene — py -3.11 examples/gfx2d_scene.py

Ops the type connects to (they accept `rgba` as input)

premultiply · alpha_composite · sprite_blit · sprite_transform · sprite_sheet_slice · nine_slice

Same category (`composite`)

premultiply · unpremultiply · alpha_composite · alpha_composite_premul · blend_mode

*Provenance: gfx2d.py — GFX2D operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*

layer_stack — GFX2D composite op