SaveImage_Canvas

SaveImage_Canvas is a save node with a phone call attached. It does what any SaveImage does - writes your IMAGE tensor to ComfyUI's output folder with PNG metadata - and then it does one more thing: it POSTs the saved file path to the canvas app's server (/getGenStatus) so the interactive canvas knows a new generation landed and can display it. That round-trip is what closes the loop on the pack's canvas workflows: paint → OutpaintCanvasTool pulls state → generate → this saves and notifies → the canvas shows the result.

It's an output node (no outputs, is_output_node true), so it belongs at the end of the graph.

How it works

The save half is ComfyUI boilerplate: folder_paths.get_save_image_path for a numbered filename under your filename_prefix, write each image as PNG with the workflow metadata embedded (unless you launched with metadata disabled). Then the canvas half fires: it builds a small JSON payload {"data": {"flag": true, "genimg": <full saved path>}} and sends it to http://{LISTEN}:{CANVASPORT}/getGenStatus - the same two environment variables (LISTEN, CANVASPORT) that OutpaintCanvasTool reads. The canvas server treats that as "a new image was generated, here's where it lives."

The inputs that matter

• images - the IMAGE tensor(s) to save.
• filename_prefix - prefix for the saved file, default ComfyUI. Files land in ComfyUI/output/<prefix>_<counter>_.png.

No outputs - it's a terminal node.

How to install it

Part of the pack, one install:

cd ComfyUI/custom_nodes
git clone https://github.com/taabata/LCM_Inpaint-Outpaint_Comfy
cd LCM_Inpaint-Outpaint_Comfy
pip install -r requirements.txt

Or ComfyUI Manager → "LCM_Inpaint_Outpaint_Comfy" → restart. If you actually want the canvas round-trip, you also need the CanvasTool server set up (the README's python setup.py step inside the CanvasTool/ folder) and LISTEN/CANVASPORT exported, because this node crashes if those environment variables aren't set.

Common issues

The env-var dependency is the whole story. This node will save your image fine and then throw on the POST if LISTEN or CANVASPORT is unset - the KeyError comes from os.environ[...], and it happens after the save, so it can look like a save failure when the file actually exists. Check your console output, then check your env.

If you don't care about the canvas app at all - say you grabbed this pack just for the LCM nodes - don't use this node. Use SaveImage_LCM or the built-in SaveImage, which have no server dependency. SaveImage_Canvas exists specifically to talk to the canvas, and it's only worth the setup if you're running the canvas loop.