<aside> 🛠

Put One Image Back Into a List — Replace by Index

The mirror of List Extract: instead of pulling one image out of a list, List Inject replaces the image at a specific position with a new one and passes the modified list downstream. Automatically resizes the replacement to fit the frame with three fit modes (cover, contain, stretch). Perfect for "extract → process → inject" pipelines where you pull one item out, enhance it, and slot it back into the original sequence.

</aside>

What it does

List Inject takes an image list and a replacement image, and returns a new list where the image at the specified 0-based index has been swapped out for the replacement. All other images in the list pass through unchanged. If the replacement image is a different resolution than the list's frame size, the tool automatically resizes it using the fit mode you choose. Result: the same list, minus one item, plus the new one — ready to feed into any downstream node that consumes a list (video reassembly, batch processors, list-based viewers).

Problem it solves

• Extract → enhance → re-inject pipelines – Pull one item from a list, run it through image models (upscale, enhance, edit), then put the improved version back where it belongs
• Frame-level video editing – Replace a specific frame in a decoded video sequence (bad frame, key frame you upscaled separately, edited hero frame)
• Swap one variant in a batch – Replace a bad or unwanted image in a batch of generated variants
• Correct a bad mask – Replace a specific mask in a segmentation stack with a hand-fixed or model-refined version
• Preserve list structure – Keep the rest of the list intact; only the specified index changes
• Handle size mismatches – Automatic resize with three fit modes means the replacement doesn't need to match the list's native resolution exactly

Input/Output

<aside>

• Input: Image list + replacement image
  • Input 1 — Image list: The original list (from a batch node, video-frame decoder, segmentation model, generation output, etc.)
  • Input 2 — Replacement image: The single image to inject into the list. Can be any resolution — the fit mode handles size differences

• Output: New image list with one item replaced

  • Format: Same list structure as the input

  • Content: All original items preserved except the one at the specified index, which is replaced by the (fit-mode-resized) replacement image

    

    (Example: in the image list, replacing the office background layer at a given index with the baseball playground layer)

• Configuration Option:

  • 0-based index of the member to replace: Which item in the list to swap.
    • Range: 0 to (list length – 1)
    • 0 – Replace the first item
    • N – Replace the (N+1)th item
    • UI: A slider you drag to the position; the current index is shown to the right
    • Behavior: Requesting an index past the end of the list may error or no-op depending on upstream behavior — stay within the list's range
  • How to fit a differently-sized replacement image to the frame resolution: Controls what happens when the replacement image has different dimensions than the list's frame size. Same idea as CSS object-fit.

  Mode	Behavior	Best For
  cover (default)	Replacement is scaled to fully cover the frame, cropping any overflow. Aspect ratio preserved.	Full-frame replacements where you want to fill every pixel, even if edges get trimmed
  contain	Replacement is scaled to fit entirely inside the frame, adding transparent letterboxing if needed. Aspect ratio preserved.	Replacements you want to keep whole — no cropping
  stretch	Replacement is stretched to exactly match frame dimensions. Aspect ratio not preserved (image may distort).	When the replacement was designed to fill any shape (backgrounds, textures)

</aside>

How to Use

1. Connect the source list → Wire the image list into the top input port
2. Connect the replacement image → Wire the single image you want to inject into the second input port
3. Set the target index → Drag the slider (or type a value) to pick which item to replace. 0 = first item.
4. Pick a fit mode → Choose cover (default), contain, or stretch based on how you want the replacement resized