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

Image Mask Crop - Mask-Boundary Cropping and Alpha Output

Node Purpose: Image Mask Crop crops by the mask’s bounding box or keeps original size, and optionally outputs alpha from the mask. Returns both the image and the processed mask, with robust batch size alignment.

Inputs

Name	Port	Type	Default	Range	Description
image	-	IMAGE	-	-	Input image batch.
mask	optional	MASK	-	-	Input mask batch. If not provided, uses the image's alpha channel.
output_alpha	-	BOOLEAN	false	-	Output RGBA with alpha from the mask when true; otherwise preserve the input image's RGB/RGBA channel count.
output_crop	-	BOOLEAN	true	-	Crop to the mask's bbox; when false, keep original image size.
pad_crop	-	INT	0	0-4096	Pad the crop region by this many pixels (only applies when output_crop=true).

Outputs

Name	Type	Description
image	IMAGE	Cropped or original-size image; RGBA if output_alpha is true.
mask	MASK	Cropped or padded mask aligned to the image output.

Features

• BBox cropping: computes bbox from mask and crops image/mask accordingly.
• Crop expansion: pad_crop expands the bbox before cropping, and the expanded area still comes from the original image rather than added black padding.
• Alpha channel: when output_alpha is true, output is RGBA with alpha from the mask. For RGBA input, output alpha is the input alpha multiplied by the mask.
• Channel preservation: when output_alpha is false, the image is only cropped and RGB is not darkened by the mask. RGB input stays RGB; RGBA input stays RGBA.
• Size preservation: when output_crop is false, keeps original size and centers/pads the mask if needed.
• Batch robustness: mismatched image/mask counts are cycled; outputs are padded to uniform sizes before stacking.

Typical Usage

• Matte extraction: set output_alpha=true to produce RGBA cutouts; downstream compositing can use alpha directly.
• Tight crops: set output_crop=true to focus on the mask region; when output_alpha=false, the input channel count is preserved.
• BBox crops: when using rectangular bbox masks with pad_crop, the expanded area preserves original image content. If output_alpha=true, that area becomes transparent according to the mask.
• Full-frame effects: set output_crop=false to maintain the original canvas and let output_alpha decide whether mask alpha is output.

Notes & Tips

• If the mask has no non-zero pixels, the node falls back to original-size outputs and applies alpha (if enabled).
• RGBA inputs keep their original alpha channel when output_alpha=false.
• Outputs are device-safe and clamped to [0,1].