---
license: other
license_name: mixed
license_link: LICENSE.md
library_name: executorch
tags:
  - executorch
  - on-device
  - image-restoration
  - inpainting
  - colorization
  - super-resolution
---

# Yesteryear models

On-device ExecuTorch builds of the models used by **Yesteryear**, a private photo restoration
app. Photos are processed on the phone; these files are downloaded by the app the first time
a feature is used.

Each model is a re-export of a published open model, converted for
[ExecuTorch](https://github.com/pytorch/executorch) 1.4 with no retraining. `*_xnnpack.pte`
files run on the CPU (XNNPACK, float32) on Android and iOS; `*_coreml.pte` files run on iOS
(Core ML, float16). LaMa and DDColor ship as XNNPACK only: their float16 Core ML builds were
not accurate enough, so iOS uses the XNNPACK files for them.

| File | Model | Purpose | Upstream license |
|---|---|---|---|
| `realesrgan_x4v3_t256_{xnnpack,coreml}.pte` | [Real-ESRGAN](https://github.com/xinntao/Real-ESRGAN) general x4v3 | 4x upscaling, 256 px tiles | BSD-3-Clause |
| `bopbtl_scratch_t384_{xnnpack,xnnpack_int8,coreml}.pte` | Scratch detection from [Bringing Old Photos Back to Life](https://github.com/microsoft/Bringing-Old-Photos-Back-to-Life) | Finds scratches and tears, 384 px | MIT |
| `lama_big_t512_xnnpack.pte` | [LaMa](https://github.com/advimman/lama) (big-lama) | Inpaints the damage, 512 px tiles | Apache-2.0 |
| `ddcolor_paper_tiny_t512_xnnpack.pte` | [DDColor](https://github.com/piddnad/DDColor) tiny | Colorization, 512 px | Apache-2.0 |

Full license texts and copyright notices are in [`licenses/`](licenses). See
[`LICENSE.md`](LICENSE.md) for details and changes made.

## Changes from upstream

The networks and weights are unchanged. To run under ExecuTorch, some operations are rewritten
as mathematically equivalent forms (verified against the upstream PyTorch models):

- LaMa: the Fourier transform is computed as matrix multiplications against fixed DFT tables.
- DDColor: layer norm, attention and pooling are written with operations XNNPACK supports;
  spectral normalization is folded into the weights.
- All: reflection padding is built from slices; inputs and outputs are wrapped for the app
  (for example, LaMa takes RGB plus a mask channel and composites its own output).

## Notes

- `bopbtl_scratch_t384_xnnpack_int8.pte` uses 8-bit weights with dynamically quantized
  activations (38 MB instead of 150 MB). Its scratch masks match the float model with IoU 0.95
  to 0.98 on test photos; the app uses it on Android.

- The LaMa and DDColor weights were trained on Places365 and ImageNet respectively; those
  datasets have their own terms of use for the images themselves.
- The Bringing Old Photos Back to Life repository states that its code and pretrained models
  are MIT licensed.