# Copy

> Copy channels from A into the B stream.

| Node | Copy |
|---|---|
| Menu | Channel › Copy |
| **Names in each format** | |
| .oink comp (JSON) | `"type": "OC_N_copy"` |
| .nk script | `Copy` ([how .nk import works](/docs/nuke-users/nk-import)) |
| Python | `nuke.createNode("Copy")` |
| Assistant (MCP) | `create_node(type="Copy")` |
| Tab search | `copy` |

![Copy properties](/shots/nodes/copy@2x.webp)

## Inputs and outputs

| Port | Name | Type |
|---|---|---|
| input 0 | B | image |
| input 1 | A | image |
| input 2 | mask | image |
| output 0 | Image | image |

## Knobs

Panel tab **Copy**, in panel order.

| Knob | Label | Type | Default | Range / values | .nk knob | Description |
|---|---|---|---|---|---|---|
| `from0` | Copy channel | text | `rgba.alpha` |  | `from0` |  |
| `to0` | to | text | `rgba.alpha` |  | `to0` |  |
| `from1` | Copy channel | text | `none` |  | `from1` |  |
| `to1` | to | text | `none` |  | `to1` |  |
| `from2` | Copy channel | text | `none` |  | `from2` |  |
| `to2` | to | text | `none` |  | `to2` |  |
| `from3` | Copy channel | text | `none` |  | `from3` |  |
| `to3` | to | text | `none` |  | `to3` |  |
| `channels` | Layer Copy | menu | `none` | rgba, rgb, alpha, all, none | `channels` | Channels copied from A to B where A has them |
| `bbox` | Set BBox to | menu | `union` | union, B side, A side | `bbox` |  |
| `metadata_from` | metadata from | menu | `B` | B, A, All | `metainput` |  |
| `range_from` | range from | menu | `B` | B, A, All | `rangeinput` |  |
| `mask_channel` | mask | menu | `none` | none, rgba.alpha, rgba.red, rgba.green, rgba.blue |  | Mask channel, e.g. rgba.alpha (none = no mask; a linked mask input then uses rgba.alpha) |
| `invert_mask` | invert | bool | `false` |  | `invert_mask` |  |
| `unpremult` | (un)premult by | menu | `none` | none, rgba.alpha | `unpremult` |  |
| `invert_unpremult` | invert | bool | `false` |  | `invert_unpremult` |  |
| `mix` | mix | float | `1` | 0 to 1 | `mix` |  |

### Other knobs (Python, .nk and the assistant; not on the panel)

| Knob | Label | Type | Default | Range / values | .nk knob | Description |
|---|---|---|---|---|---|---|
| `gl_color` | Viewer Controls Color | float ×3 | `0, 0, 0` | 0 to 1 |  |  |
| `postage_stamp_frame` | Static Frame | int | `1` | -2147483648 to 2147483647 |  |  |
| `lifetimeStart` | Lifetime Start | int | `0` | -2147483648 to 2147483647 |  |  |
| `lifetimeEnd` | Lifetime End | int | `100` | -2147483648 to 2147483647 |  |  |
| `useLifetime` | Use Lifetime | boolean | `false` |  |  |  |
| `cached` | Cached | boolean | `false` |  |  |  |
| `bookmark` | Bookmark | boolean | `false` |  |  |  |
| `dope_sheet` | Dope Sheet | boolean | `false` |  |  |  |
| `clone_group` | Clone Group | string |  |  |  |  |
| `link_source` | Link Source | string |  |  |  |  |
| `link_overrides` | Link Overrides | string |  |  |  |  |
| `split_views` | Split Views | string |  |  |  |  |

## Knob names in .nk scripts

| .nk knob | Knob here |
|---|---|
| `metainput` | `metadata_from` |
| `rangeinput` | `range_from` |

Other .nk knobs use the same name here. See [.nk import](/docs/nuke-users/nk-import).

## Examples

Open these from **Help › Examples…**, or from the **?** menu in this node's Properties panel.

- **Copy an alpha between streams** (`examples/channel/copy_alpha.oink`): Copy takes rgba.alpha from its A input (the CandleGlass render) and writes it into the B stream (the Desk photo), then Premult multiplies the colour by that alpha. The same pattern moves any channel between streams.


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Sources: opencomp_core/nodes/merge/copy.py, opencomp_electron/src/components/properties/knobSchema.ts, opencomp_core/nk/mapping.py