> Language: [中文文档](./README-zh.md)

ComfyUI-FairLab

A collection of 58 utility nodes for ComfyUI, spanning string processing, image I/O and manipulation,
arithmetic logic, PBR material tooling, and workflow diagnostics.
All nodes conform to the ComfyUI IO.* type annotation convention.

---

- [Overview](#overview) - [Installation](#installation) - [Prerequisites](#prerequisites) - [Method 1: ComfyUI Manager](#method-1-comfyui-manager-recommended) - [Method 2: Manual](#method-2-manual-installation) - [Verify Installation](#verify-installation) - [Updating](#updating) - [Dependencies](#dependencies) - [Troubleshooting](#troubleshooting) - [Node Reference](#node-reference) - [String](#string-16-nodes) - [Image](#image-26-nodes) - [Logic](#logic-11-nodes) - [Utility](#utility-5-nodes) - [Technical Notes](#technical-notes) - [License](#license) ---

Overview

ComfyUI-FairLab supplements the core ComfyUI node set with operations that are commonly needed in production workflows but not available in the base distribution. | Category | Nodes | Scope | |:----------|:-----|:------| | String | 16 | String construction, tag manipulation, translation, encoding repair, file I/O | | Image | 26 | File/URL/Base64 loading, batch I/O, video conversion, alpha & channel ops, PBR maps, modulation | | Logic | 11 | Arithmetic operators, conditional branching, type casting | | Utility | 5 | Diagnostic printing, aspect ratio presets, dual LoRA loading, sandboxed scripting | ---

Installation

Prerequisites

- **ComfyUI** installed and working. If not, follow the [official guide](https://github.com/comfyanonymous/ComfyUI#installing). - **Python** 3.10+ (the same environment ComfyUI uses). - **Git** (for manual installation).

Method 1: ComfyUI Manager (Recommended)

1. Open ComfyUI and navigate to the **Manager** panel. 2. Click **Install Custom Nodes**. 3. Search for `ComfyUI-FairLab`. 4. Click **Install** and restart ComfyUI.

Method 2: Manual Installation

```bash # 1. Navigate to the custom_nodes directory cd ComfyUI/custom_nodes # 2. Clone the repository git clone https://github.com/yanhuifair/ComfyUI-FairLab.git # 3. Enter the project directory cd ComfyUI-FairLab # 4. Install dependencies pip install -r requirements.txt # 5. Restart ComfyUI ```

Verify Installation

After restarting ComfyUI, double-click the canvas and search for `FairLab` or any node name (e.g., `String Append`, `Load Image Batch From Directory`). If the nodes appear in the search results, the installation was successful.

Updating

**ComfyUI Manager:** Click **Update All** in the Manager panel. **Manual:** ```bash cd ComfyUI/custom_nodes/ComfyUI-FairLab git pull pip install -r requirements.txt ```

Dependencies

| Package | Required By | |:--------|:------------| | `googletrans` | String Translate | | `opencv-python` | Video ↔ image; general processing | | `requests` | Download Image, Load Image From URL | | `nest_asyncio` | Async event loop support | | `perfect-pixel[opencv]>=0.1.4` | Perfect Pixel |

Troubleshooting

**Nodes not showing up after installation** - Make sure you restarted ComfyUI after installing. - Check the ComfyUI terminal for import errors related to `ComfyUI-FairLab`. - Verify that dependencies were installed: `pip list | grep -E "opencv|googletrans|perfect-pixel"` **ImportError: No module named 'cv2'** ```bash pip install opencv-python ``` **Google Translate not working** The `googletrans` library may require an updated version. Try: ```bash pip install --upgrade googletrans ``` ---

Node Reference

String (16 nodes)

String construction, persistence, and tag-oriented manipulation. | Node | Description | |:-----|:------------| | **String** | Emit a constant string value | | **Int** | Emit a constant integer value | | **Float** | Emit a constant floating-point value | | **String Append** | Concatenate multiple input strings into a single output | | **Load String** | Read string content from a local text file | | **Save String To Directory** | Write a string to a file on disk | | **Load String From Directory** | Read a string from a file in a specified directory | | **Show String** | Display a string value on the node's UI panel for inspection | | **String Translate** | Translate strings via Google Translate (source/target language configurable) | | **Fix UTF-8 String** | Repair malformed UTF-8 byte sequences (e.g., mojibake from encoding mismatches) | | **Range String** | Generate a sequence of indexed strings over a numeric range (e.g., `frame_001`..`frame_100`) | | **Prepend Tags** | Insert a prefix before each tag in a comma-separated list | | **Append Tags** | Append a suffix to each tag in a comma-separated list | | **Exclude Tags** | Remove specified tags from a tag list | | **Unique Tags** | Deduplicate entries in a tag list | | **ASCII Art Text** | Render text as an ASCII-art image using system fonts |

Image (26 nodes)

I/O & Loading

| Node | Description | |:-----|:------------| | **Load Image From Directory** | Load a single image from a directory | | **Load Image Batch From Directory** | Load all images from a directory as a batch tensor | | **Load Image From URL** | Fetch an image directly from a remote URL into a tensor | | **Download Image** | Download a remote image and persist it to local disk | | **Save Image To Directory** | Write an image tensor to a specified output path | | **Save Image To Folder** | Save images organized by subdirectory | | **Image To Base64** | Encode an image tensor as a Base64 string | | **Base64 To Image** | Decode a Base64 string into an image tensor |

Processing

| Node | Description | |:-----|:------------| | **Resize Image** | Resize an image tensor to target dimensions | | **Image Size** | Output the width and height of an image as scalar values | | **Image Shape** | Output the full tensor shape `[B, C, H, W]` of an image batch | | **Image Remove Alpha** | Strip the alpha channel from an RGBA image, producing RGB | | **Fill Alpha** | Add or replace the alpha channel on an RGB image | | **Pure Color Image** | Generate a solid-color image of configurable dimensions and RGB value | | **Images Range** | Slice a sub-range of images from a batch by start/end index | | **Images Index** | Extract a single image from a batch by index | | **Images Cat** | Concatenate multiple image batches along the batch dimension | | **Outpainting Pad** | Pad image borders for outpainting workflows | | **Perfect Pixel** | Integer-scale an image without sub-pixel interpolation (nearest-neighbor at exact multiples) |

Video

| Node | Description | |:-----|:------------| | **Video To Image** | Extract frames from a video file as an image batch tensor | | **Image To Video** | Compose an image batch into a video file (configurable FPS) |

Modulation

| Node | Description | |:-----|:------------| | **Modulation** | Apply error-diffusion modulation (Floyd–Steinberg-style halftoning) | | **Modulation Direction** | Directional error-diffusion with configurable scan direction and speed |

PBR Maps

| Node | Description | |:-----|:------------| | **Mask Map** | Convert a grayscale image into a normalized mask tensor | | **Detail Map** | Generate a detail map from an input image for PBR material pipelines | | **Roughness To Smoothness** | Convert between roughness and smoothness maps (invert) |

Logic (11 nodes)

Arithmetic and control-flow primitives for node-graph-level computation. | Node | Description | |:-----|:------------| | **Number** | Generic numeric constant (INT / FLOAT toggle) | | **Add** | `A + B` with automatic INT/FLOAT type resolution | | **Subtract** | `A - B` | | **Multiply** | `A × B` with automatic type resolution | | **Multiply Int** | `A × B` with result cast to INT | | **Divide** | `A ÷ B` | | **Max** | `max(A, B)` | | **Min** | `min(A, B)` | | **If** | Conditional branch: route to output A or B based on a boolean condition | | **Float To Int** | Cast FLOAT to INT (truncation) | | **Int To Float** | Cast INT to FLOAT |

Utility (5 nodes)

Diagnostics, presets, and extensibility. | Node | Description | |:-----|:------------| | **Print Any** | Print any input value to the console for debugging | | **Print Image** | Print image tensor metadata to the console (shape, dtype, value range) | | **Aspect Ratios** | Dropdown selector for common aspect ratios (1:1, 16:9, 4:3, 3:2, 2:3, 21:9) | | **Load LoRA Dual** | Load two LoRA models simultaneously with independent strength parameters | | **Python Script** | Evaluate a restricted Python expression in an AST-whitelist sandbox; supports arithmetic, comparison operators, and a curated set of builtins (`abs`, `min`, `max`, `round`, `len`, etc.). `exec` and `eval` are explicitly disabled. | ---

Technical Notes

**Python Script sandbox** The expression evaluator uses an AST whitelist that permits only explicitly registered operators (`+`, `-`, `*`, `/`, `//`, `%`, `**`, `<`, `>`, `<=`, `>=`, `==`, `!=`, `is`, `is not`, `not`, unary `+`/`-`) and built-in functions (`abs`, `bool`, `float`, `int`, `len`, `max`, `min`, `round`, `sorted`, `str`, `sum`, `tuple`, `list`). Arbitrary code execution via `exec` or `eval` is not possible. **IO typing** All nodes use the ComfyUI `IO.*` type annotations (`IO.STRING`, `IO.IMAGE`, `IO.INT`, `IO.FLOAT`, etc.), ensuring compatibility with the modern ComfyUI type system. **ASCII Art Text** Requires system font support. On minimal Linux installations, install a font package (e.g., `fonts-dejavu-core` on Debian/Ubuntu). **Video operations** Frame extraction and composition rely on `opencv-python`. Processing time scales with resolution and frame count. ---

Name	Type	Default	Description
front	STRING		—
back	STRING		—

String Append

Inputs (2)

Outputs (1)