Pin Types

ArcBrush uses a typed pin system to ensure that only compatible nodes can be connected. Each pin type represents a different kind of data flowing through the graph.

The Five Pin Types

Each pin type uses a distinct shape and color so you can tell them apart at a glance. Shapes never change when a pin is connected — they’re tied to the type, not the connection state.

Pin Type	Shape	Color	Description
Image	■ Filled square	Orange	RGBA image data (the most common type)
Mask	● Filled circle	Blue	Single-channel grayscale mask
Palette	▲ Filled triangle	Violet	Named color slot collection
Variants	▢ Outlined square	Gold	Multiple image outputs from palette remapping
Size Reference	○ Outlined circle	Teal	Dimensional reference (width/height)

Connection Rules

Most connections require matching pin types, with a few useful exceptions:

From (output)	To (input)	Rule
Image	Image	Direct connection.
Mask	Mask	Direct connection.
Palette	Palette	Direct connection.
Variants	Variants	Direct connection.
Mask	Image	Auto-promoted. The grayscale mask is converted to RGBA and a small indicator appears mid-wire.
Image	Mask	Not allowed. Use Mask From Image to extract a mask from an image’s alpha or luminance.
Image or Mask	Size Reference	The Size Reference pin accepts both — it just reads the connected node’s dimensions.

The graph blocks invalid wiring as you drag, and an inline toast explains why if you try to make a forbidden connection.

Common patterns:

Most nodes have Image inputs and outputs.
Palette Remap takes an Image + Palette and outputs Variants.
Export Batch takes Variants to export all palette colors at once.
Keyer nodes (Chroma Key, Luma Key) expose a matte Mask output you can route directly into mask inputs — no Mask From Image needed.

Pin Naming Conventions

When you hover a pin, the name hints at how it’s used:

image — the primary image input or output.
alpha — a generic single-channel input (often interchangeable with a mask).
mask — a mask input that restricts where the node’s effect applies.
matte — a mask output produced by a keyer node (Chroma Key, Luma Key).
palette — a Palette pin connecting a Palette node to a remapper or exporter.
size_ref — a Size Reference pin that drives output dimensions.

Pin Indicators

Input pins appear on the left side of a node.
Output pins appear on the right side.
Connected pins are filled; unconnected pins are hollow (the shape is the same either way).
Hover over a pin to see its type and name.