BMAB Blend

Not every image-combining job needs a mask. Sometimes you just want two images mixed at a fixed ratio, the way you'd crossfade between two photos in an editor - and that's exactly what this node does, no more and no less.

What it is and why you'd reach for it

BMAB Blend takes two images and mixes them at a uniform opacity across the whole frame, controlled by a single alpha value. There's no mask, no per-pixel transparency, no edge - every pixel gets the same mix ratio. That makes it the simpler sibling of BMAB Alpha Composit, which sits right next to it in the pack and does the masked, per-pixel version of a similar idea.

Reach for Blend when you want a flat crossfade: averaging two generations to split the difference between them, softening a strong stylistic pass by mixing it partway back toward the original, or building a quick ghosting/double-exposure effect. Reach for Alpha Composit instead when you need a real layered composite - pasting a foreground subject over a background with a clean, mask-defined edge. If you find yourself wanting different parts of the image to blend by different amounts, you've outgrown this node and want the masked one.

How it works

Standard linear interpolation between two images: at alpha 0 you get pure image1, at alpha 1 you get pure image2, and everything in between is a proportional mix. It's the same math behind any "opacity slider" you've used in an image editor, applied uniformly across the whole canvas.

Inputs and outputs

• image1 (required) - the first image in the mix.
• image2 (required) - the second image in the mix.
• alpha (required, default 0.5, range 0–1) - the mix ratio. 0.5 is an even 50/50 split; push it toward 0 or 1 to favor one image over the other.

Output: a single blended image.

Installing it

Through ComfyUI Manager: search comfyui_bmab, install, and restart ComfyUI. Manual install:

cd ComfyUI/custom_nodes
git clone https://github.com/portu-sim/comfyui_bmab.git
cd comfyui_bmab
pip install -r requirements.txt

(Windows portable users: python_embeded\python.exe -m pip install -r requirements.txt.) This node has no dependency on either of BMAB's optional companion packs (comfyui_controlnet_aux, ComfyUI_IPAdapter_plus) - it's plain image math, so the base install is all you need.

Common issues

There's very little that goes wrong with a two-input blend, but a couple of things are worth knowing:

• Different-sized inputs. If image1 and image2 aren't the same resolution, blending them can produce unexpected results or an outright error - resize one to match the other before feeding them in.
• Reaching for Blend when you actually wanted a masked composite. If your result looks like a flat, uniform ghosting effect when you were expecting a clean layered image with one subject sitting on top of another, you want BMAB Alpha Composit instead - that's the node built for mask-based layering rather than a whole-image opacity mix.
• Alpha at the extremes. Setting alpha to exactly 0 or 1 gives you back one of the source images unchanged, which is sometimes a useful way to A/B test a downstream effect without rewiring the graph.