ComfyUI-LocalFolderImage

Local Folder Image (client folder)

A ComfyUI custom node that lets the user pick a folder on their own machine and, on every workflow run, uploads exactly one file from it to the server.

Basic workflow:

<img src="examples/basic.png" alt="Basic Local Folder Image workflow" width="800">

Background

Not long ago, I found that I had collected many old images generated with older models such as SD 1.5 and SDXL.

Most of these images were low quality, had many defects, and were saved at a low resolution. I wanted to use a modern model to improve them and increase their resolution. To build a kind of automatic fix-and-upscale process.

However, I did not want to upload this huge number of files to the server. So I started thinking: why not create a node that uses a local folder as the file source and uploads only one new file to the server every time the workflow starts?

This would allow me to process all the files automatically using the Run Instant mode.

At first, I was not sure whether this was even possible. However, with the help of Claude, a solution was found that did exactly what I needed: it went through the files in a local folder one by one, without uploading all of them to the server.

It is not perfect, but it handled my task very well.

The workflow I used to upscale the images with Krea 2:

<img src="examples/krea2_upscale.png" alt="Krea2 upscaler workflow" width="800">

I know that using the QwenImageEdit text encoder with Krea 2 is not completely correct, but it still works.

Installation

ComfyUI/custom_nodes/ComfyUI-LocalFolderImage/
├── __init__.py
├── nodes.py
└── js/
    └── local_folder_image.js

Restart ComfyUI, then hard-reload the page (Ctrl+Shift+R) -- the frontend caches extensions aggressively.

Usage

1. Add Local Folder Image (client folder) (category image/loaders).
2. Click Pick folder... and choose a directory. Chrome will ask something like "Upload 1000 files to this site?" -- that is expected, nothing is actually transferred at this point.
3. Queue Prompt. The folder selection persists for as many runs as you like.
4. After a page reload the folder has to be picked again (one click; the dialog reopens at the last used directory).

Ignore this warning:

<img src="examples/warning.png" alt="Annoying warning window" width="458">

Your files won't be uploaded anywhere, this is a default browser confirmation for the folder select dialog.

Parameters

| Parameter | Meaning | |---|---| | file_index | 1-based position of the file to load, within the sorted and filtered list. Upper bound is tightened to the real file count once a folder is picked. | | index_mode | What happens to file_index after the run: fixed, increment, decrement, random. | | loop | Whether to wrap around at the ends of the list. Forced on and greyed out for fixed and random. | | scan | top_level -- only the root of the picked folder; recursive -- include subfolders. | | extensions | Comma-separated extension filter. | | filename | Filled in automatically; shows the file that was actually uploaded. |

index_mode, loop, scan and extensions are read by the frontend; the backend ignores them and only consumes filename.

Index semantics

file_index behaves like a seed with control_after_generate: the value shown on the node is the one used by the current run, and it is updated afterwards for the next one.

| Situation | Result | |---|---| | file_index < 1 or > file count | Error. The run is never queued. | | fixed | The index never changes. | | random | Next index is uniform over 1..count. Repeats are possible. | | increment, index < count | Next index is index + 1. | | increment, index == count, loop on | Next index is 1. | | increment, index == count, loop off | Current run still executes; the next queue attempt fails with "all N files have been iterated". | | decrement, index > 1 | Next index is index - 1. | | decrement, index == 1, loop on | Next index is the file count. | | decrement, index == 1, loop off | Same as above: the next queue attempt fails. |

Once exhausted, the button label shows - exhausted. Editing file_index, toggling loop, changing index_mode or picking a folder again clears that state.

With a batch count above 1 the frontend builds each queued item separately, so a batch of 4 in increment mode consumes four consecutive files.

Outputs

IMAGE, MASK (from the alpha channel, empty when there is none), filename (STRING) and file_index (INT, the index actually used).

How it works

Queue Prompt
  └─ patched app.graphToPrompt()
       ├─ filter and sort the stored File references
       ├─ validate file_index against the file count
       ├─ POST /upload/image  (type=temp, subfolder=artemko7v_local_folder_image)
       ├─ write the uploaded path into the filename widget
       └─ advance file_index per index_mode / loop
  └─ normal prompt serialisation -> server
       └─ Python node reads the file from the temp directory

<input type="file" webkitdirectory> yields an array of File objects, which are lazy handles to data on disk rather than the bytes themselves. A thousand of them cost roughly a megabyte. Only the selected file is ever read, and fetch streams it off disk, so the tab's peak memory does not scale with folder size.

Files are sorted with a natural, locale-aware comparison, so img2 precedes img10. input.files has no guaranteed order, and a stable order is what makes file_index meaningful across runs.

Limitations

• The workflow must be queued from the browser. Queueing over the API or from a script means nobody uploads a file, and the node fails with FileNotFoundError.
• The folder selection does not survive a page reload. This is the intended behaviour.
• The folder selection is not saved in the workflow JSON. That is a property of the model, not a bug.
• webkitdirectory is always recursive. top_level filters the results in the frontend, but the browser's confirmation dialog will still count subfolders.
• A File is a snapshot taken at pick time. If the file has since been deleted or rewritten, the run fails with the offending index named. No silent substitution: that would break the index contract.
• Uploads land in temp, not input, so ComfyUI clears them on restart.

Troubleshooting

• No button on the node -> the extension did not load. Check that WEB_DIRECTORY points at ./js and hard-reload.
• "no folder selected" on queue -> the folder was picked before a page reload.
• To confirm a file arrived, look in ComfyUI/temp/artemko7v_local_folder_image/.