Preview Panels

Preview Panels is the visual checkpoint for everything after the layout stage. While Preview Panel Layout shows you the abstract cut tree, this node shows you the concrete panel polygons - after you've built them, rotated them, scaled them, eroded them. It's the "look before you generate" node, and in a workflow where one bad panel shape costs you a full page render, it earns its keep.

It renders the panel list as an image: each polygon filled with a translucent color, black edges, and the panel's index stamped in a numbered circle at its centroid. That index matters more than it looks like - panel order in this pack follows reading order, so the stamps tell you at a glance whether your page reads the way you intend, left-to-right or right-to-left.

The inputs are minimal by design:

• panels - the list of polygons (from Build Layout Panels, or after you've pushed them through Rotate/Scale/Skew/Offset).
• canvas (optional) - a single polygon (usually your page canvas from Canvas Panel) drawn as the white background. Without it you still see the panels; with it you see where they sit relative to the page, which is exactly what you want when checking gutters and margins.

There are no outputs - it's an output node, terminal, its job is to show you the picture in ComfyUI's preview area.

The workflow habit to build: always preview before generating. The whole chain - crop panels, generate art, paste back - assumes the geometry is right. A panel that overlaps its neighbor or pokes off the page will produce a crop that doesn't match its bbox, and Paste Crops with Masks will either resize it (softening it) or misalign it. The preview is where you catch that at the cost of one click instead of one render.

One honest note on rendering: it goes through matplotlib, so the preview is a proportional drawing, not a pixel-exact representation of any particular canvas resolution. If you've set a specific canvas size in Canvas Panel, that's the data - the preview just visualizes it. And because the canvas is optional, panels drawn without one will still be stamped with their indices, so you can also use this node purely as a "which panel is which" inspector while building list operations.

Installing

Part of comfyui-panels by bmad4ever. Via ComfyUI Manager (search "comfyui-panels") and restart, or:

cd ComfyUI/custom_nodes
git clone https://github.com/bmad4ever/comfyui_panels

Deps: shapely, matplotlib, opencv-python - no models, no GPU. Shapely is pinned exactly; version clashes with other packs are the realistic import failure.