Anything Crop (for Swap)

Object swapping is a three-act play: cut the thing out, generate a replacement, stitch it back in so the seams don't show. Anything Crop (for Swap) is the first act - the node that finds the object, crops tightly around it, and packages everything downstream needs to undo the crop later. If you've ever hand-cropped a face into a paint editor, generated a patch, and spent an hour fighting the seam back into the original, this is the node that automates that ritual.

It's the first half of WorkflowX's Anything Swap bridge, and it's built on SAM3 - the "Segment Anything" successor that ComfyUI shipped native support for. The design philosophy is worth stating: the crop node emits an opaque SWAP_STITCH payload carrying the clean original and the exact geometry, so the stitch node can put things back pixel-perfectly even if the swap model returns a totally different resolution.

How it works

With use_sam3 on (the default), the node runs SAM3 internally: it loads the SAM3 checkpoint you pick, prompts it with a short concrete noun like "face" or "left hand", and gets back object masks. It then measures the bounding box, expands it per expand_factor (1.4 is a good default - 1.0 hugs the object so tight that your swap model has no context), snaps dimensions to the padding multiple, and crops.

The important contract: the stitch output carries the original image, the pre- and post-resize sizes, and the exact crop geometry. Anything Stitch reads that payload and composites the replacement back without ever asking you to re-align anything. detected (BOOLEAN) tells you whether SAM3 found anything - branch on it to skip downstream work when the mask comes back empty.

Inputs that matter

• image (IMAGE) - single image, not a batch.
• use_sam3 + sam3_prompt + sam3_checkpoint - the segmentation path. Turn use_sam3 off to feed your own mask instead.
• expand_factor / expand_pixels - crop breathing room. force_square squares the crop (right for faces, wasteful for a bottle) and is required if resize_mode is target_size.
• swap_prompt (STRING) - the edit instruction, with {target} {width} {height} {caption} tokens substituted on output.

Outputs

crop (IMAGE), crop_mask (MASK), swap_prompt (STRING), source_masked (IMAGE - source with the object blanked, great for preview or an inpaint pass), stitch (SWAP_STITCH), and detected (BOOLEAN).

Install

Part of WorkflowX-Configurator - Manager search WorkflowX Configurator, or:

cd ComfyUI/custom_nodes
git clone https://github.com/haroonaslam/WorkflowX-Configurator

Restart, hard-refresh. The heavy dependency is the model, not the code: you need a SAM3.1 checkpoint in ComfyUI/models/checkpoints/ (e.g. sam3.1_multiplex_fp16.safetensors, from huggingface.co/Comfy-Org/sam3.1), plus a ComfyUI build that includes native SAM3 support (merged in Comfy-Org/ComfyUI#13408). The node will tell you when that's missing.

Common issues

• "SAM3_Detect not found" - your ComfyUI predates native SAM3. Update ComfyUI, or set use_sam3 off and wire your own mask.
• Nothing detected / junk mask. Lower isn't always better - threshold at 0.5 is a sane floor; below that you find more and more garbage. Use select_mode and object_index to pick among several matches.
• Prompt too long. Short concrete nouns beat sentences for SAM3. "face", "shoe", "sunglasses".

One trap worth naming: source_masked blanks the object out, which is not what you want to feed the swap model - that wants the clean crop. Keep the two straight. And remember the Anything Swap approach is detection-crop-rerender-paste: the same loop the detailing ecosystem has run for years, just with a swap model in the middle instead of a face restorer.