Add guide for finding FastAI-compatible colorization models - Document how to find models with .pkl files - Add instructions for setting MODEL_ID - Note current model limitation

FASTAI_MODEL_GUIDE.md

@@ -0,0 +1,74 @@
+# FastAI-Compatible Colorization Models Guide
+
+## Current Issue
+
+The model `Hammad712/GAN-Colorization-Model` contains a PyTorch model (`generator.pt`), not a FastAI model. FastAI models must be `.pkl` files created with FastAI's `export()` function.
+
+## How to Find FastAI-Compatible Models
+
+### Option 1: Search Hugging Face
+
+1. Go to https://huggingface.co/models
+2. Search for: `fastai colorization` or `fastai image colorization`
+3. Look for models that have `.pkl` files in their repository
+4. Check the model's README to confirm it's a FastAI Learner
+
+### Option 2: Use FastAI's Official Examples
+
+FastAI course examples often have colorization models. Look for:
+- FastAI course lesson notebooks on image colorization
+- Models exported using `learn.export('model.pkl')`
+
+### Option 3: Train Your Own
+
+If you have a FastAI colorization model:
+```python
+from fastai.vision.all import *
+learn = ... # your trained model
+learn.export('model.pkl')
+```
+
+Then upload `model.pkl` to Hugging Face.
+
+## Setting a New Model
+
+### Via Environment Variable (Recommended)
+
+In your Hugging Face Space settings, add:
+```
+MODEL_ID=your-username/your-fastai-colorization-model
+```
+
+### Via Code
+
+Update `app/config.py`:
+```python
+MODEL_ID: str = os.getenv("MODEL_ID", "your-username/your-fastai-colorization-model")
+```
+
+## Model Requirements
+
+The model must:
+1. ✅ Be a FastAI Learner exported as `.pkl` file
+2. ✅ Accept PIL Images as input
+3. ✅ Return colorized images (PIL Image or tensor)
+4. ✅ Be uploaded to Hugging Face Hub
+
+## Testing a Model
+
+Before switching, you can test locally:
+```python
+from huggingface_hub import from_pretrained_fastai
+from PIL import Image
+
+learn = from_pretrained_fastai("your-model-id")
+img = Image.open("test.jpg")
+result = learn.predict(img)
+```
+
+If this works, the model is compatible!
+
+## Alternative: Switch Back to SDXL+ControlNet
+
+If you can't find a FastAI model, you can switch back to the SDXL+ControlNet approach which was working before. Update `MODEL_BACKEND` to `"diffusers"` and use a ControlNet colorization model.
+

app/config.py

@@ -18,6 +18,9 @@ class Settings(BaseSettings):
     BASE_URL: str = os.getenv("BASE_URL", "http://localhost:8000")
     
     # Model / inference settings
+    # Note: MODEL_ID must point to a FastAI model (.pkl file), not PyTorch (.pt file)
+    # To find FastAI-compatible colorization models, search Hugging Face for models with .pkl files
+    # Example: Look for models tagged with "fastai" and "colorization"
     MODEL_ID: str = os.getenv("MODEL_ID", "Hammad712/GAN-Colorization-Model")
     MODEL_BACKEND: str = os.getenv("MODEL_BACKEND", "fastai")
     BASE_MODEL_ID: str = os.getenv("BASE_MODEL_ID", "stabilityai/stable-diffusion-xl-base-1.0")