---
datasets:
- danjacobellis/LSDIR_540
---
# Wavelet Learned Lossy Compression (WaLLoC)

WaLLoC sandwiches a convolutional autoencoder between time-frequency analysis and synthesis transforms using 
CDF 9/7 wavelet filters. The time-frequency transform increases the number of signal channels, but reduces the temporal or spatial resolution, resulting in lower GPU memory consumption and higher throughput. WaLLoC's training procedure is highly simplified compared to other $\beta$-VAEs, VQ-VAEs, and neural codecs, but still offers significant dimensionality reduction and compression. This makes it suitable for dataset storage and compressed-domain learning. It currently supports 1D and 2D signals, including mono, stereo, or multi-channel audio, and grayscale, RGB, or hyperspectral images.

## Installation

1. Follow the installation instructions for [torch](https://pytorch.org/get-started/locally/)
2. Install WaLLoC and other dependencies via pip

```pip install walloc PyWavelets pytorch-wavelets```

## Pre-trained checkpoints

Pre-trained checkpoints are available on [Hugging Face](https://huggingface.co/danjacobellis/walloc).

## Training

Access to training code is provided by request via [email.](mailto:danjacobellis@utexas.edu)

## Usage example


```python
import os
import torch
import matplotlib.pyplot as plt
import numpy as np
from PIL import Image, ImageEnhance
from IPython.display import display
from torchvision.transforms import ToPILImage, PILToTensor
from walloc import walloc
from walloc.walloc import latent_to_pil, pil_to_latent
class Config: pass
```

### Load the model from a pre-trained checkpoint

```wget https://hf.co/danjacobellis/walloc/resolve/main/RGB_Li_27c_J3_nf4_v1.0.2.pth```


```python
device = "cpu"
checkpoint = torch.load("RGB_Li_27c_J3_nf4_v1.0.2.pth",map_location="cpu",weights_only=False)
codec_config = checkpoint['config']
codec = walloc.Codec2D(
    channels = codec_config.channels,
    J = codec_config.J,
    Ne = codec_config.Ne,
    Nd = codec_config.Nd,
    latent_dim = codec_config.latent_dim,
    latent_bits = codec_config.latent_bits,
    lightweight_encode = codec_config.lightweight_encode
)
codec.load_state_dict(checkpoint['model_state_dict'])
codec = codec.to(device)
codec.eval();
```

### Load an example image

```wget "https://r0k.us/graphics/kodak/kodak/kodim05.png"```


```python
img = Image.open("kodim05.png")
img
```




    
![png](https://huggingface.co/danjacobellis/walloc/resolve/main/README_files/README_6_0.png)
    



### Full encoding and decoding pipeline with .forward()

* If `codec.eval()` is called, the latent is rounded to nearest integer.

* If `codec.train()` is called, uniform noise is added instead of rounding.


```python
with torch.no_grad():
    codec.eval()
    x = PILToTensor()(img).to(torch.float)
    x = (x/255 - 0.5).unsqueeze(0).to(device)
    x_hat, _, _ = codec(x)
ToPILImage()(x_hat[0]+0.5)
```




    
![png](https://huggingface.co/danjacobellis/walloc/resolve/main/README_files/README_8_0.png)
    



### Accessing latents


```python
with torch.no_grad():
    codec.eval()
    X = codec.wavelet_analysis(x,J=codec.J)
    Y = codec.encoder(X)
    X_hat = codec.decoder(Y)
    x_hat = codec.wavelet_synthesis(X_hat,J=codec.J)

print(f"dimensionality reduction: {x.numel()/Y.numel()}×")
```

    dimensionality reduction: 7.111111111111111×



```python
Y.unique()
```




    tensor([-7., -6., -5., -4., -3., -2., -1., -0.,  1.,  2.,  3.,  4.,  5.,  6.,
             7.])




```python
plt.figure(figsize=(5,3),dpi=150)
plt.hist(
    Y.flatten().numpy(),
    range=(-7.5,7.5),
    bins=15,
    density=True,
    width=0.9);
plt.title("Histogram of latents")
plt.xticks(range(-7,8,1));
plt.xlim([-7.5,7.5])
```




    (-7.5, 7.5)




    
![png](https://huggingface.co/danjacobellis/walloc/resolve/main/README_files/README_12_1.png)
    


# Lossless compression of latents


```python
def scale_for_display(img, n_bits):
    scale_factor = (2**8 - 1) / (2**n_bits - 1)
    lut = [int(i * scale_factor) for i in range(2**n_bits)]
    channels = img.split()
    scaled_channels = [ch.point(lut * 2**(8-n_bits)) for ch in channels]
    return Image.merge(img.mode, scaled_channels)
```

### Single channel PNG (L)


```python
Y_padded = torch.nn.functional.pad(Y, (0, 0, 0, 0, 0, 9))
Y_pil = latent_to_pil(Y_padded,codec.latent_bits,1)
display(scale_for_display(Y_pil[0], codec.latent_bits))
Y_pil[0].save('latent.png')
png = [Image.open("latent.png")]
Y_rec = pil_to_latent(png,36,codec.latent_bits,1)
assert(Y_rec.equal(Y_padded))
print("compression_ratio: ", x.numel()/os.path.getsize("latent.png"))
```


    
![png](https://huggingface.co/danjacobellis/walloc/resolve/main/README_files/README_16_0.png)
    


    compression_ratio:  15.171345894154717


### Three channel WebP (RGB)


```python
Y_pil = latent_to_pil(Y,codec.latent_bits,3)
display(scale_for_display(Y_pil[0], codec.latent_bits))
Y_pil[0].save('latent.webp',lossless=True)
webp = [Image.open("latent.webp")]
Y_rec = pil_to_latent(webp,27,codec.latent_bits,3)
assert(Y_rec.equal(Y))
print("compression_ratio: ", x.numel()/os.path.getsize("latent.webp"))
```


    
![png](https://huggingface.co/danjacobellis/walloc/resolve/main/README_files/README_18_0.png)
    


    compression_ratio:  16.451175633838172


### Four channel TIF (CMYK)


```python
Y_padded = torch.nn.functional.pad(Y, (0, 0, 0, 0, 0, 9))
Y_pil = latent_to_pil(Y_padded,codec.latent_bits,4)
display(scale_for_display(Y_pil[0], codec.latent_bits))
Y_pil[0].save('latent.tif',compression="tiff_adobe_deflate")
tif = [Image.open("latent.tif")]
Y_rec = pil_to_latent(tif,36,codec.latent_bits,4)
assert(Y_rec.equal(Y_padded))
print("compression_ratio: ", x.numel()/os.path.getsize("latent.tif"))
```


    
![jpeg](README_files/README_20_0.jpg)
    


    compression_ratio:  12.40611656815935



```python
!jupyter nbconvert --to markdown README.ipynb
```

    [NbConvertApp] Converting notebook README.ipynb to markdown
    [NbConvertApp] Support files will be in README_files/
    [NbConvertApp] Making directory README_files
    [NbConvertApp] Writing 6024 bytes to README.md



```python
!sed -i 's|!\[png](README_files/\(README_[0-9]*_[0-9]*\.png\))|![png](https://huggingface.co/danjacobellis/walloc/resolve/main/README_files/\1)|g' README.md
```