app.py

import gradio as gr
import numpy as np
from sklearn.cluster import MiniBatchKMeans
from sklearn.utils import shuffle
from PIL import Image
import os
import tempfile
from io import BytesIO

def compress_kmeans(image: np.ndarray, k: int, random_state: 42) -> np.ndarray:
    """
    Faster K‑Means compression using a random pixel sample for centroid fitting.
    """
    pixels = image.reshape(-1, 3).astype(np.float32)

    sample_size = min(20000, len(pixels))
    sample = shuffle(pixels, random_state=random_state)[:sample_size]

    model = MiniBatchKMeans(
        n_clusters=k,
        batch_size=min(1024, sample_size),
        n_init='auto',
        max_iter=50,
        random_state=random_state,
        verbose=0,
    )
    model.fit(sample)

    labels = model.predict(pixels)
    centres = model.cluster_centers_.astype(np.uint8)
    compressed_pixels = centres[labels]

    return compressed_pixels.reshape(image.shape)

def process(filepath, k):
    if filepath is None:
        return None, "Please upload an image.", None

    # Load original
    orig = np.array(Image.open(filepath).convert('RGB'))

    # Compress
    comp = compress_kmeans(orig, k, random_state=42)

    def get_size(img):
        with BytesIO() as buf:
            Image.fromarray(img).save(buf, format='PNG')
            return len(buf.getvalue())

    orig_size = get_size(orig)
    comp_size = get_size(comp)
    ratio = orig_size / comp_size
    saved = (1 - comp_size/orig_size) * 100

    # PSNR
    mse = np.mean((orig.astype(float) - comp.astype(float)) ** 2)
    psnr = 20 * np.log10(255.0 / np.sqrt(mse)) if mse > 0 else float('inf')

    stats = (f"**Original:** {orig_size/1024:.1f} KB  \n"
             f"**Compressed:** {comp_size/1024:.1f} KB  \n"
             f"**Compression ratio:** {ratio:.1f}x  \n"
             f"**Space saved:** {saved:.1f}%  \n"
             f"**PSNR:** {psnr:.1f} dB")

    temp = tempfile.mkdtemp()
    out_path = os.path.join(temp, 'compressed.png')
    Image.fromarray(comp).save(out_path)

    return comp, stats, out_path

iface = gr.Interface(
    fn=process,
    inputs=[
        gr.Image(type='filepath', label='Upload an Image'),
        gr.Slider(minimum=2, maximum=64, step=2, value=16, label='Number of colours (k)')
    ],
    outputs=[
        gr.Image(label='Compressed Image'),
        gr.Markdown(label='Compression Statistics'),
        gr.File(label='Download Compressed Image')
    ],
    title='Image Compression with K‑Means',
    description='Reduce the number of colours in an image using K-Means clustering.'
)

iface.launch()