---
license: agpl-3.0
library_name: collectorvision
tags:
- onnx
- object-detection
- card-detection
- mobilevit
base_model: apple/mobilevit-xx-small
---

# Cornelius — CCG Card Corner Detector

MobileViT-XXS corner detector trained to locate the four corners of a CCG card
(Magic: The Gathering, Pokémon, etc.) in a photograph or video frame.

## Model details

| Property | Value |
|---|---|
| Architecture | MobileViT-XXS + global-token SimCC head |
| Input | 384×384 RGB, ImageNet-normalised |
| Outputs | corners (8 floats, normalised [0,1]), compatibility presence logit, sharpness scalar |
| Parameters | ~1.06M |
| File size | 4.2 MB (fp32 ONNX, simplified) |
| Local CPU speed | 23.2 ms / frame, 43.0 FPS (ONNX Runtime CPU, single thread, 384×384) |
| Codename | cornelius |
| Latest version | 2.12 |

## Versions

| File | Notes |
|---|---|
| `cornelius-2.12.onnx` / `model.onnx` | Global-token SimCC production model. Smaller than 1.x (~1.06M params vs ~1.82M) and substantially more robust under rotation/occlusion. Full-rotation stress: mean IoU 0.970411, p10 0.954621, 0 bad, 0 collapse. |
| `cornelius-1.221.onnx` | Fixed SimCC coordinate decoding to use peak argmax instead of soft expectation. This addresses rotated-card failures where multi-modal corner distributions decoded to implausible between-peak coordinates; see [CollectorVision issue #24](https://github.com/HanClinto/CollectorVision/issues/24). |
| `cornelius-1.210.onnx` | Earlier beta-test candidate. Combined held-out IoU 0.8857. |

## Evaluation

All IoU values are quadrilateral IoU between predicted and labelled card corners.
`bad` counts predictions with IoU `< 0.5`; `collapse` counts geometrically
degenerate predictions where two predicted corners nearly coincide.

### Release comparison

| Version | Architecture | Params | ONNX size | Normal held-out IoU | Full ±50° rotation mean / p10 | Full-rotation bad / collapse | Notes |
|---|---:|---:|---:|---:|---:|---:|---|
| 2.12 | MobileViT-XXS + global-token SimCC | ~1.06M | 4.2 MB | 0.968911 | 0.970411 / 0.954621 | 0 / 0 | Current default `model.onnx`; selected production checkpoint. |
| 1.221 | MobileViT-XXS + independent SimCC | ~1.82M | 7.1 MB | — | 0.933910 / 0.928732 | 138 / 91 | Strong normal detector, but vulnerable to rotation-induced corner collapse. |
| 1.210 | MobileViT-XXS + independent SimCC | ~1.82M | 7.1 MB | 0.8857 combined | — | — | Earlier beta; reported combined held-out IoU 0.8857. |

### Cornelius vs fastweb-single

Cornelius remains the stable, conservative default. The `fastweb-single`
family is also available through the stable channel for consumers that explicitly
select it; it is a smaller EfficientViT-B0 global-token SimCC detector being
evaluated as a faster replacement candidate. Both models use the same 384×384
input contract and produce `corners`, compatibility `presence`, and `sharpness`
outputs.

| Model | Channel | Normal test IoU | Normal collapse | Full ±50° mean / p10 IoU | Full-rotation bad / collapse | ONNX size | Params | Local CPU speed |
|---|---|---:|---:|---:|---:|---:|---:|---:|
| Cornelius 2.12 | stable | **0.968911** | 18 | 0.970411 / 0.954621 | **0 / 0** | 4.41 MB | 1.05M | 23.2 ms / 43.0 FPS |
| fastweb-single 1.39 | stable + testing | 0.968839 | **13** | **0.974255 / 0.960757** | 1 / 0 | **3.19 MB** | **0.77M** | **8.4 ms / 119.4 FPS** |

Takeaways:

- Normal accuracy is effectively tied: fastweb-single trails Cornelius by
  0.000072 IoU on the normal held-out test.
- fastweb-single is about 28% smaller on disk and about 2.8× faster in the
  local single-thread CPU benchmark.
- fastweb-single has stronger rotation-stress mean and p10 IoU, but still has
  one remaining bad rotation-stress case where Cornelius has zero.
- The current published fastweb-single ONNX uses the same argmax SimCC decoding
  style; small post-hoc parabolic peak-refinement gains were observed in local
  experiments but are not baked into this artifact.

Speed benchmark details: ONNX Runtime 1.24.4, CPUExecutionProvider,
`intra_op_num_threads=1`, `inter_op_num_threads=1`, 50 warmup runs and 300 timed
runs on a 384×384 float32 input. These numbers are intended for model-to-model
comparison on the same machine, not as universal device benchmarks.

### Cornelius 2.12 checkpoint selection

The 2.12 release was selected from a low-LR continuation because it best balanced
normal accuracy and stress robustness:

| Checkpoint | Normal test IoU | Normal collapse | Full ±50° mean IoU | p10 IoU | bad | collapse |
|---|---:|---:|---:|---:|---:|---:|
| epoch 9 | 0.968923 | 19 | 0.968892 | 0.952787 | 1 | 0 |
| **epoch 12 / 2.12** | **0.968911** | **18** | **0.970411** | **0.954621** | **0** | **0** |
| epoch 14 | 0.968777 | 18 | 0.968660 | 0.952481 | 0 | 0 |

### Occlusion + rotation smoke test

Three hand-picked occlusion stress samples were swept through the same full
rotation preset. The 2.12 numbers below are from the Hugging Face-downloaded
`model.onnx`.

| Model | Mean IoU | p10 IoU | bad | collapse |
|---|---:|---:|---:|---:|
| Cornelius 2.12 | 0.888789 | 0.795696 | 0 | 0 |
| Frozen global-token prototype | 0.772039 | 0.673141 | 0 | 0 |
| Hydra4 reduce4_h64 prototype | 0.736071 | 0.648447 | 0 | 0 |
| Cornelius 1.x baseline | 0.687937 | 0.406498 | 22 | 21 |

Per-sample Cornelius 2.12 results:

| Sample | Mean IoU | p10 IoU | min IoU | bad | collapse |
|---|---:|---:|---:|---:|---:|
| Ingenious Skaab | 0.963076 | 0.951756 | 0.939898 | 0 | 0 |
| LTR 566 | 0.883024 | 0.847024 | 0.836244 | 0 | 0 |
| Wall of Fire | 0.820269 | 0.779252 | 0.763541 | 0 | 0 |

## Outputs

- **corners** — 8 floats `[x0,y0, x1,y1, x2,y2, x3,y3]` in TL→TR→BR→BL order, normalised [0,1]
- **presence** — compatibility logit. For 2.x this is a constant `1.0`; prefer the sharpness gate.
- **sharpness** — mean peak of the 8 SimCC softmax distributions; use this for card-present gating.

## Usage

The easiest way to use Cornelius is through the [CollectorVision](https://github.com/HanClinto/CollectorVision) library, which wires it into a full detect → dewarp → embed → identify pipeline:

```python
import collector_vision as cvg

cvid = cvg.Identifier(cvg.HFD("HanClinto/milo", "scryfall-mtg"))
result = cvid.identify("photo.jpg")
print(result.ids)  # {"scryfall_id": "..."}
```

### Direct ONNX usage

```python
import onnxruntime as ort
import numpy as np
from PIL import Image

session = ort.InferenceSession("model.onnx")

# Preprocess: resize to 384×384, ImageNet normalise, NCHW float32
img = Image.open("photo.jpg").convert("RGB").resize((384, 384))
x = np.array(img, dtype=np.float32) / 255.0
x = (x - [0.485, 0.456, 0.406]) / [0.229, 0.224, 0.225]
x = x.transpose(2, 0, 1)[None]  # (1, 3, 384, 384)

corners, presence, sharpness = session.run(None, {"image": x})
# corners: (1, 8) — x0,y0,x1,y1,x2,y2,x3,y3 normalised [0,1], TL→TR→BR→BL
# presence: (1,) — compatibility logit; use sharpness instead for gating
# sharpness: (1,) — mean peak of the 8 SimCC softmax distributions

if sharpness[0] > 0.02:
    pts = corners[0].reshape(4, 2)
```

## Part of CollectorVision

Used together with [HanClinto/milo](https://huggingface.co/HanClinto/milo) in the [CollectorVision](https://github.com/HanClinto/CollectorVision) inference library.