1hew-ComfyUI-1hewNodes/web/docs/1hew_MaskToBBoxMask/en.md

Mask To BBox Mask - Convert Mask to BBox Mask

Node Purpose: Mask To BBox Mask converts foreground regions in a mask into minimum bounding rectangle masks. It is useful for turning an object-shaped mask into a square/rectangular bbox mask that encloses the object.

Inputs

Name	Port	Type	Default	Range	Description
mask	-	MASK	-	-	Input mask batch; 2D inputs are expanded to [B,H,W].
output_mode	-	COMBO	merge	merge / separate	merge outputs one bbox per input mask; separate outputs one bbox mask per connected region.
divisible_by	-	INT	8	1-1024	Expands the rectangle width and height outward until they are divisible by this value; it never shrinks the original foreground area.

Outputs

Name	Type	Description
bbox_mask	MASK	Converted rectangular bbox masks.

Features

• Bounding rectangle: computes the minimum enclosing rectangle from all non-zero foreground pixels and fills it white.
• Divisible sizing: uses divisible_by to expand bbox width and height to the requested multiple; near image edges, expansion shifts toward available space.
• Merged output: merge combines all valid foreground in each input mask into one bbox.
• Separate output: separate creates bbox masks per 8-connected region, so the output batch may be larger than the input batch.

Typical Usage

• Object boxing: convert a detailed object mask into a rectangular mask around it.
• Crop/paste workflows: feed the result into nodes such as Mask Crop by BBox Mask or Image Paste by BBox Mask.
• Multi-object handling: use Mask Separate first, then convert each object mask into a stable rectangular area.

Notes & Tips

• If an input mask has no non-zero foreground, merge outputs an all-black mask.
• If the image itself is smaller than the aligned target size, the bbox expands within image bounds and prioritizes keeping the original foreground intact.
• If one mask contains multiple distant objects, merge creates one large rectangle around all of them. Use separate or Mask Separate when each object needs its own bbox.