Shrink PowerPoint Slides (.pptx file) by reducing images size inside

shrink.py

import os
import io
import zipfile
from PIL import Image
from tqdm import tqdm


QUALITY = 50   # Adjust as needed: 1–95


def shrink_image(data, filename, prt=print):
    """Shrink JPEG/PNG binary data using Pillow."""
    try:
        img = Image.open(io.BytesIO(data))

        out = io.BytesIO()

        if filename.lower().endswith(".png"):
            # Convert PNG to PNG with lower quality by reducing dimensions OR using optimize
            # Pillow has no 'quality' for PNG, so we use optimize=True
            img.save(out, format="PNG", optimize=True)
        elif filename.lower().endswith(".jpeg") or filename.lower().endswith(".jpg"):
            # JPEG quality reduction
            img.save(out, format="JPEG", quality=QUALITY, optimize=True)
        else:
            raise RuntimeError

        out_bytes = out.getvalue()
        shrink_pct = 100 - len(out_bytes)/len(data)*100
        shrink_size_kb = (len(data) - len(out_bytes)) / 1000
        to_shrink = (shrink_pct > 10) or (shrink_size_kb > 100)
        if to_shrink:
            prt(f"{filename}: shrunk {len(data)/1000:.2f} → {len(out_bytes)/1000:.2f} KB ({100 - len(out_bytes)/len(data)*100:.1f}%)")
            return out_bytes
        else:
            prt(f"{filename}: shrunk {len(data)/1000:.2f} → {len(out_bytes)/1000:.2f} KB ({100 - len(out_bytes)/len(data)*100:.1f}%), using original...")
            return data
    except Exception as e:
        prt(f"Skipping {filename}: {e}")
        return data


def slim_pptx(input_pptx):
    """Create a slimmed version of a PPTX with resized images."""
    output_pptx = input_pptx.replace(".pptx", "_slim.pptx")
    pbar = None

    with zipfile.ZipFile(input_pptx, 'r') as zin, \
        zipfile.ZipFile(output_pptx, 'w', zipfile.ZIP_DEFLATED) as zout:

        items = zin.infolist()
        shrinkable = [item for item in items if (item.filename.startswith("ppt/media/") and item.filename.lower().endswith((".jpg", ".jpeg", ".png")))]
        if not shrinkable:
            exit('Nothing to shrink!')
        pbar = tqdm(shrinkable)
        for item in zin.infolist():
            filedata = zin.read(item.filename)

            # Only target ppt/media/*.jpg / .jpeg / .png
            if item.filename.startswith("ppt/media/") and \
               item.filename.lower().endswith((".jpg", ".jpeg", ".png")):
                pbar.set_description(f"Shrinking: {item.filename}")
                filedata = shrink_image(filedata, item.filename, pbar.write)
                pbar.update(1)

            zout.writestr(item, filedata)

    # if pbar:
    #     prt = pbar.write
    # else:
    #     prt = print
    prt = pbar.write  # guaranteed
    prt(f"\nDone! Slim PPTX saved as: {output_pptx}")


if __name__ == "__main__":
    import sys
    if len(sys.argv) < 2:
        print("Usage: python shrink.py input.pptx")
        exit(1)

    slim_pptx(sys.argv[1])