Handwriting Video Env Check

Handwriting Video Env Check is the pack's own first-aid kit, and for once the README's advice to run it first is right. The whole pack is one fixed template video, a renderer, and four Python packages - and when one of those is missing, the main node fails with a wall of traceback instead of telling you what's wrong. This node exists to skip that. You wire it up, hit run, and it prints a little report of what the renderer needs and whether it's actually there.

Reading the source, the check is honest and narrow. It tries to import the four packages from requirements.txt - cv2, PIL, numpy, imageio_ffmpeg - and reports each as OK or FAILED with the exception. Then it imports the renderer module itself, and finally checks that templates/fixed_template.mp4 shipped with your install, printing the template path either way. All of it comes back as one multi-line string.

One trap that will absolutely trip you the first time: this node is not an output node. ComfyUI only executes nodes whose outputs feed something that runs, so if you drop Env Check into a fresh graph and press go, nothing happens. Wire the report string into a text-display node - the classic Show Text / Text Output - and it'll actually fire. That's the whole workflow: Env Check → text display.

The single input, run_check (BOOLEAN, default true), is a bypass switch: flip it to false and you get a one-line check skipped instead of a report. Handy if a node upstream keeps forcing the check to re-run, mildly pointless otherwise.

Installing it

Same story as the whole pack - it ships in one repo, hyt131331-creator/ComfyUI-Handwriting-Video-Replace. Easiest route is ComfyUI Manager: search "ComfyUI-Handwriting-Video-Replace", install, restart. Manager will pull the dependencies from requirements.txt for you. A bare manual clone will not:

cd ComfyUI/custom_nodes
git clone https://github.com/hyt131331-creator/ComfyUI-Handwriting-Video-Replace
# then, if you skipped Manager:
pip install -r ComfyUI-Handwriting-Video-Replace/requirements.txt

Dependencies are light - opencv-python, Pillow, numpy, imageio-ffmpeg - and there are no model files to hunt down. One caveat: this pack is written for RunningHub, the cloud ComfyUI platform, and there you don't clone anything yourself - RunningHub installs custom nodes on request, so you'd ask the platform to add it rather than running the commands above.

Reading the report

• A FAILED line means that package didn't import. Install it and restart ComfyUI.
• template video: MISSING means the templates/ folder didn't come with your clone or got deleted. The main node cannot function without it; re-clone.
• All OK does not guarantee a successful render. The check tests the renderer import, not the font - and this pack's renderer hard-requires a handwriting TTF (assets/aaa.TTF) that the README lists but the repo doesn't actually ship. That fails at render time, after this check has already given you the all-clear. If Env Check is green and the replace node still dies, that missing font is the first place to look.

It's a utility node with zero fanfare - zero search impressions on comfy.icu, a single-commit repo from one author - but for a pack whose one real failure mode is "dependency missing," thirty seconds with it beats ten minutes of reading a traceback.