featlens 0.1.0

Model-agnostic feature-map visualization: PCA-to-RGB feature maps from any vision model and any layer.

FeatLens

See what any vision model encodes. FeatLens renders PCA-to-RGB feature maps for any vision model — DINO, DINOv2/v3, CLIP, SigLIP, MAE, DeiT, V-JEPA, CNNs, … — loaded from any source (timm, HuggingFace transformers, torch.hub, an external repo, or a model you built yourself), and from any layer, as a clean model × layer grid.

Most "DINO PCA" scripts are welded to one model. FeatLens separates representation access (a small adapter layer over the model zoo) from visualization (robust PCA → RGB), so you can point it at a new model in seconds and compare models/layers side by side.

Gallery

All produced by examples/quickstart.py on the three bundled images. Sizes below are the originals; each image is resized to img_size (default 224) before the model.

visualize(...) — DINO ViT-B/16 feature maps across layers 2 / 5 / 8 / 11:

Image (original size)	Source	Feature maps
astronaut.jpg · 512×512
cat.jpg · 451×300
coffee.jpg · 600×400

grid(...) — model × layer, overlaid on the image (DINO vs DINOv2 across layers 2/5/8/11):

compare(...) — models at the final layer  |  custom_adapter — a ResNet-50 (CNN escape hatch)

  

Install

pip install -e ".[timm]"          # timm backend (DINO, CLIP, SigLIP, DeiT, ...)
# extras: [hf] transformers · [clip] open_clip · [all]

Install PyTorch for your platform first (https://pytorch.org).

Quick start (Python)

import featlens as ll

# One model, scrub layers (shared PCA basis -> colors comparable across the row)
ll.visualize("dinov2_vitb14", "img.jpg", layers=[2, 5, 8, 11], out="row.png")

# Compare models at the final layer (per-tile basis)
ll.compare(["dino_vitb16", "mae_vitb16", "clip_large_openai"], "img.jpg", layer=-1, out="cmp.png")

# Full model x layer grid, overlaid on the image
ll.grid(["dino_vitb16", "dinov2_vitb14"], "img.jpg", layers=[2, 5, 8, 11], overlay=True, out="grid.png")

Quick start (CLI)

featlens --models dino_vitb16 clip_large_openai --layers 2 5 8 11 \
    --images examples/images/cat.jpg --mode grid --out out/grid.png
featlens --config configs/example.yaml --images examples/images/cat.jpg --out out/grid.png

Image size & resizing

Images are resized to a square img_size × img_size before the model (default 224). img_size must be divisible by the model's patch size (multiples of 16 for patch-16 models, 14 for patch-14). Larger sizes give a finer feature grid at more compute:

ll.visualize("dinov2_vitb14", "img.jpg", layers=[2, 5, 8, 11], img_size=448)   # 32x32 grid

For non-square images, choose how aspect ratio is handled with resize_mode:

resize_mode	behavior
squash (default)	resize straight to img_size² — may distort
crop	resize shortest side to img_size, center-crop — aspect preserved
pad	resize longest side to img_size, pad to square — keeps the whole image

ll.grid([...], "wide.jpg", resize_mode="crop")          # Python

featlens --models dino_vitb16 --images wide.jpg --resize-mode pad --img-size 448 --out g.png

(FeatureGrid(interpolation_size=…) is separate — it only upscales the rendered tiles, not the model input.)

Model sources

Source	How to pass it	Needs
timm	friendly name (dinov2_vitb14) or raw id (vit_base_patch16_224)	[timm]
HuggingFace	hf:facebook/dinov2-base	[hf]
torch.hub (V-JEPA)	vjepa2_vitl16	network for weights
External repo (VGGT/SPA/…)	external_adapter.load(repo_dir, builder, hook_target=…)	the cloned repo
Your own model	custom_adapter.load(model, feature_fn=…)	—

Friendly names (see featlens/registry.py) cover DINO, DINOv2/v3, CLIP, SigLIP, MAE, DeiT, Perception Encoder and V-JEPA; any other timm id works directly.

Layers

layers=[2, 5, 8, 11] selects transformer block indices (0-based, negatives allowed, -1 = last). The same convention holds across backends — for HuggingFace models FeatLens maps block i to hidden_states[i+1] (skipping the embedding output) for you.

Bring your own model

Anything that isn't built in works through the escape hatch — give a feature function or a hook target. CNNs work for free (their conv map is already spatial):

import torch.nn as nn, torchvision
from featlens import FeatureExtractor, FeatureGrid
from featlens.adapters import custom_adapter

resnet = torchvision.models.resnet50(weights="DEFAULT")
trunk = nn.Sequential(*list(resnet.children())[:-2])           # -> [B, 2048, h, w]
lm = custom_adapter.load(trunk, patch_size=32, feature_fn=lambda m, x: m(x), name="resnet50")
FeatureGrid([FeatureExtractor(lm)]).render("img.jpg", out_path="resnet50.png")

For a model in its own repo, external_adapter.load(repo_dir, builder, hook_target="blocks") puts the repo on sys.path, builds the model, and hooks its blocks.

How it works

1. Adapters resolve a spec → a LoadedModel and drive extraction in one of three modes: forward hooks on per-block modules (ViTs/CNNs/V-JEPA), HF output_hidden_states, or a user callable.
2. tokens_to_grid normalizes whatever a layer emits ([B,N,D] tokens with optional CLS/register prefixes, or [B,D,h,w] maps) into a dense [B,D,h,w] grid.
3. Robust PCA (median-absolute-deviation outlier filtering) projects features to RGB; FeatureGrid lays out the model × layer tiles with a per-tile or shared-per-model basis.

The extraction core adapts the FrozenBackbone pattern; the PCA is adapted from the SpaRRTa feature-map script.

Releasing

Releases publish to PyPI automatically via .github/workflows/publish.yml (PyPI Trusted Publishing — no API token stored in the repo).

One-time setup on PyPI: add a trusted publisher for the project (Account → Publishing) with owner turhancan97, repository FeatLens, workflow publish.yml, environment pypi. PyPI supports a pending publisher so the very first release can also go through Actions.

Then cut a release by pushing a tag:

# bump the version in pyproject.toml first, then:
git tag v0.1.0 && git push origin v0.1.0

The workflow builds the sdist + wheel, runs twine check, and uploads to PyPI.

License

MIT.