Easy Image Batch — behavior matrix

Status: Canonical (approved 2026-06-18). Implemented in k_easy_image_batch.py and mirrored in docs/user_guide/nodes/koolook_image/easy_image_batch.md.

Runnable demo: the Easy Image Batch — Select and Rebuild workflow bundled in the Kforge Labs Workflows sidebar folder (docs/workflows/kforge-labs-workflows/, from #248). It supersedes the generated demo removed here.

This captures the agreed changes:

keyframe_batch → keyframes_insert (rename; the old name remains as a deprecated alias input so workflows saved on 0.4.1/0.4.2 keep loading).
No image source connected → clean placeholder batch sized by new width/height widgets (no error).
Insert-over-source mode — keyframes_insert + source_batch composite the inserts over the source cut window.
image1–image4 are "super-overwrites" — when connected they replace whatever is at their index in every mode (top priority). When not connected they do nothing (the old "pull from source_batch via imageN_frame" fallback — Mode 2 — is removed).

The layered model (single source of truth)

The output is built in three layers, lowest first. A later layer overwrites an earlier one at the same output index.

output index i  ↔  VFX frame v = cut_start_frame + i        (window: i in [0, total_frames))

┌─ Layer 3 — SUPER-OVERWRITE (image1–image4) ────────────────┐  highest priority
│  Each CONNECTED imageN → placed at index (imageN_frame      │
│  − cut_start_frame). Wins over everything. Unconnected      │
│  slots contribute NOTHING. (imageN_frame matters only       │
│  when imageN is connected.)                                 │
├─ Layer 2 — SEQUENCE ───────────────────────────────────────┤
│  • keyframes_insert connected (INSERT): i-th incoming frame │
│    → i-th source_frames position (ascending, deduped).      │
│  • else (SELECT): each source_frames number N picks         │
│    source_batch[N−1] → index (N − cut_start_frame).         │
├─ Layer 1 — BACKGROUND ─────────────────────────────────────┤  lowest priority
│  • insert-over-source (keyframes_insert AND source_batch):  │
│    source_batch cut window (index i ← source_batch[v−1];    │
│    frames beyond the source fall back to placeholder).      │
│  • otherwise: placeholder_color everywhere.                 │
└─────────────────────────────────────────────────────────────┘

Background rule. Layer 1 is the source cut window whenever source_batch is connected and either an insert is active (keyframes_insert) or the source_frames list is empty; otherwise it is placeholder_color.

What counts as "placed" (drives alpha_batch, selected_image_batch, selected_frames): normally the Layer 2 placements and Layer 3 overwrites; the Layer 1 source_batch backdrop is not placed (just the background). So alpha_batch is 0.0 at sequence inserts/picks and connected-slot overwrites, 1.0 everywhere else (flipped by invert_alpha).

Select passthrough is the exception (row 5). When the source passes through with an empty list, the covered source frames are kept content (alpha 0.0), and the uncovered tail becomes the selection (alpha 1.0, emitted in selected_*) — an extend-a-clip inpaint mask. The selection here is the gap, the inverse of every other row. Insert-mode passthrough (row 9) keeps the plain backdrop semantics (nothing placed).

Resolution / dtype come from the first connected image (insert: from keyframes_insert; select: image1 → source_batch → image2…4). With no image connected at all, the output is sized by the width/height widgets (channels = 3), on CPU/float — a clean placeholder batch.

Tie-break: if two connected slots target the same index, the higher-numbered slot wins (image4 > … > image1). Sequence + slot at the same index → the slot wins (Layer 3 > Layer 2).

Mode matrix

Legend — keyframes_insert = KI, source_batch = SB, source_frames list = list, connected image1–4 = slots.

#	KI	SB	list	slots	Background	Placed (alpha 0.0)	`selected_*`	Mode label
1	✗	✗	—	none	placeholder (`width`×`height`)	nothing	empty	clean batch
2	✗	✓	has	none	placeholder	source picks at listed positions	the picks	select
3	✗	✗	—	some	placeholder	connected slots	the slots	select (slots)
4	✗	✓	has	some	placeholder	source picks + slots (slots win on overlap)	picks + slots	select
5	✗	✓	empty	none	source cut window	covered source (kept)	the uncovered gap	source passthrough / extend
6	✓	✗	has	none	placeholder	scattered inserts	the inserts	offset / reconstruct
7	✓	✗	empty	none	placeholder	nothing	empty	clean (nothing inserted)
8	✓	✓	has	none	source cut window	scattered inserts (overwrite source)	the inserts	insert-over-source
9	✓	✓	empty	none	source cut window	nothing	empty	source passthrough
10	✓	✓	has	some	source cut window	inserts + slots (slots win)	inserts + slots	insert-over-source
11	any	any	any	set but NOT connected	(per above)	slots contribute nothing	(per above)	(per above)

Row 11 was the bug fixed here: a slot with a non-default imageN_frame that is not wired has zero effect on the output. The old behaviour (an unconnected slot pulling from source_batch) is gone.

Edge cases & logging

List ranges. N-M (e.g. 14-17) expands inclusively; a descending M-N, an over-wide range (more than 8192 frames), or any non-integer token warns and is skipped. Applies in both modes.
List set but no image source (select): the list is ignored and a clean placeholder batch is returned, with a console warning (not a silent drop).
List token not in source_batch (select): warn + skip that number.
List/insert position outside the cut window: dropped, summarized once.
More inserts than list positions / more positions than inserts: reported as "extra insert frames" / "positions with no insert frame".
source_batch shorter than the cut window (insert-over-source): the uncovered tail frames stay placeholder; count reported.
Empty list in an insert mode: clean placeholder (no SB) or clean source passthrough (with SB) — console note "frame list is empty".
Mismatched H/W/C among connected inputs: hard ValueError (unchanged).
Every run still prints one summary line: mode, cut window, placed count, and any of the notes above.

Decisions (resolved)

Tie-break direction — higher-numbered slot wins (image4 > image1); a slot beats a sequence pick / insert at the same index (Layer 3 > Layer 2).
Empty-list passthrough (select) — source_batch + an empty list passes the source cut window through (row 5). Covered source frames are kept content (alpha 0.0); a source shorter than the output leaves a placeholder tail that becomes the selection (selected_*) — an extend/inpaint mask. The selection here is the gap, the inverse of other rows.
Mode-2 fallback removed — an unconnected slot never pulls from source_batch; imageN_frame is only a placement target for a wired image.
Range syntax — the frame list accepts inclusive ranges (14-17 → 14,15,16,17) in both select and insert; descending/non-integer tokens warn.