app.py

"""
Image Compressor Pro — Python Backend (FastAPI + Pillow)
========================================================
A high-performance, concurrent image compression API designed to replace
the Node.js + Sharp backend. Uses Pillow (with pillow-heif for HEIF/AVIF)
and FastAPI with StreamingResponse for efficient, non-blocking I/O.

Deployment target: HuggingFace Spaces (Docker) or local testing.
"""

import io
import logging
from contextlib import asynccontextmanager
from concurrent.futures import ThreadPoolExecutor

from fastapi import FastAPI, Request, Query, HTTPException
from fastapi.middleware.cors import CORSMiddleware
from fastapi.responses import StreamingResponse, PlainTextResponse
from starlette.concurrency import run_in_threadpool

from PIL import Image

# ---------------------------------------------------------------------------
# Optional: HEIF / AVIF support via pillow-heif
# ---------------------------------------------------------------------------
try:
    import pillow_heif
    pillow_heif.register_heif_opener()   # enables Image.open() for HEIF/AVIF
    HEIF_AVAILABLE = True
except ImportError:
    HEIF_AVAILABLE = False

# ---------------------------------------------------------------------------
# Logging
# ---------------------------------------------------------------------------
logging.basicConfig(
    level=logging.INFO,
    format="%(asctime)s | %(levelname)-7s | %(message)s",
    datefmt="%H:%M:%S",
)
log = logging.getLogger("compressor")

# ---------------------------------------------------------------------------
# Thread pool — used to offload CPU-bound Pillow work
# ---------------------------------------------------------------------------
MAX_WORKERS = 4
_pool = ThreadPoolExecutor(max_workers=MAX_WORKERS)

# ---------------------------------------------------------------------------
# Lifespan (startup / shutdown)
# ---------------------------------------------------------------------------
@asynccontextmanager
async def lifespan(app: FastAPI):
    log.info("Compressor backend starting (workers=%d)", MAX_WORKERS)
    if HEIF_AVAILABLE:
        log.info("pillow-heif is available — HEIF/AVIF support enabled")
    else:
        log.warning("pillow-heif not installed — HEIF/AVIF output disabled")
    yield
    _pool.shutdown(wait=False)
    log.info("Compressor backend shut down")

# ---------------------------------------------------------------------------
# App
# ---------------------------------------------------------------------------
app = FastAPI(
    title="Image Compressor Pro API",
    version="1.0.0",
    lifespan=lifespan,
)

# CORS — allow all origins so the frontend can call from any domain
app.add_middleware(
    CORSMiddleware,
    allow_origins=["*"],
    allow_credentials=True,
    allow_methods=["*"],
    allow_headers=["*"],
)

# ---------------------------------------------------------------------------
# Constants
# ---------------------------------------------------------------------------
MAX_FILE_SIZE = 20 * 1024 * 1024  # 20 MB

# MIME types for each supported output format
MIME_MAP = {
    "jpeg": "image/jpeg",
    "png":  "image/png",
    "webp": "image/webp",
    "avif": "image/avif",
    "heif": "image/heic",
    "tiff": "image/tiff",
    "gif":  "image/gif",
    "bmp":  "image/bmp",
    "ico":  "image/x-icon",
    "jp2":  "image/jp2",
}

# ---------------------------------------------------------------------------
# Core compression logic (runs in thread pool)
# ---------------------------------------------------------------------------
def _compress_image(raw_bytes: bytes, quality: int, fmt: str) -> bytes:
    """
    Open *raw_bytes* as an image, compress it into *fmt* at the given
    *quality*, and return the resulting bytes.

    This is intentionally a **synchronous** function because Pillow is
    CPU-bound.  It is called via ``run_in_threadpool`` so the event loop
    is never blocked.
    """
    img = Image.open(io.BytesIO(raw_bytes))

    # Convert RGBA → RGB for formats that don't support alpha
    if fmt in ("jpeg", "tiff", "bmp", "jp2") and img.mode in ("RGBA", "LA", "PA"):
        background = Image.new("RGB", img.size, (255, 255, 255))
        background.paste(img, mask=img.split()[-1])  # alpha composite
        img = background
    elif fmt in ("jpeg", "bmp", "jp2") and img.mode not in ("RGB", "L"):
        img = img.convert("RGB")
    elif fmt == "gif" and img.mode == "RGBA":
        # GIF supports palette transparency; convert RGBA → P with transparency
        img = img.convert("RGBA")  # ensure consistent mode
        alpha = img.split()[-1]
        img = img.convert("RGB").convert("P", palette=Image.ADAPTIVE, colors=255)
        mask = Image.eval(alpha, lambda a: 255 if a <= 128 else 0)
        img.paste(255, mask)  # map transparent pixels to index 255
        # transparency index will be set during save

    out_buffer = io.BytesIO()

    if fmt == "jpeg":
        img.save(
            out_buffer,
            format="JPEG",
            quality=quality,
            optimize=True,
            progressive=True,
            subsampling="4:2:0" if quality < 90 else "4:4:4",
        )
    elif fmt == "png":
        # PNG quality mapped to compress_level (0-9, higher = smaller)
        compress_level = max(1, min(9, 9 - (quality // 12)))
        img.save(
            out_buffer,
            format="PNG",
            compress_level=compress_level,
            optimize=True,
        )
    elif fmt == "webp":
        img.save(
            out_buffer,
            format="WEBP",
            quality=quality,
            method=4,  # 0-6, higher = slower + better compression
        )
    elif fmt == "avif":
        if not HEIF_AVAILABLE:
            raise ValueError("AVIF output requires pillow-heif (not installed)")
        img.save(
            out_buffer,
            format="AVIF",
            quality=quality,
        )
    elif fmt == "heif":
        if not HEIF_AVAILABLE:
            raise ValueError("HEIF output requires pillow-heif (not installed)")
        img.save(
            out_buffer,
            format="HEIF",
            quality=quality,
        )
    elif fmt == "tiff":
        img.save(
            out_buffer,
            format="TIFF",
            compression="tiff_lzw",  # lossless LZW compression
        )
    elif fmt == "gif":
        # Preserve animated GIF frames if present
        n_frames = getattr(img, 'n_frames', 1)
        if n_frames > 1:
            frames = []
            durations = []
            for i in range(n_frames):
                img.seek(i)
                frame = img.copy()
                if frame.mode != "P":
                    frame = frame.convert("RGBA").convert("P", palette=Image.ADAPTIVE, colors=256)
                frames.append(frame)
                durations.append(img.info.get('duration', 100))
            frames[0].save(
                out_buffer,
                format="GIF",
                save_all=True,
                append_images=frames[1:],
                duration=durations,
                loop=img.info.get('loop', 0),
                optimize=True,
            )
        else:
            if img.mode not in ("P", "L"):
                img = img.convert("P", palette=Image.ADAPTIVE, colors=256)
            img.save(
                out_buffer,
                format="GIF",
                optimize=True,
            )
    elif fmt == "bmp":
        if img.mode not in ("RGB", "L", "1"):
            img = img.convert("RGB")
        img.save(
            out_buffer,
            format="BMP",
        )
    elif fmt == "ico":
        # ICO spec limits dimensions to 256×256
        max_ico = 256
        if img.width > max_ico or img.height > max_ico:
            img.thumbnail((max_ico, max_ico), Image.LANCZOS)
        if img.mode != "RGBA":
            img = img.convert("RGBA")
        img.save(
            out_buffer,
            format="ICO",
        )
    elif fmt == "jp2":
        if img.mode not in ("RGB", "L", "RGBA"):
            img = img.convert("RGB")
        img.save(
            out_buffer,
            format="JPEG2000",
            quality_mode="rates",
            quality_layers=[quality],
        )
    else:
        raise ValueError(f"Unsupported format: {fmt}")

    out_buffer.seek(0)
    return out_buffer.getvalue()

# ---------------------------------------------------------------------------
# Routes
# ---------------------------------------------------------------------------

@app.get("/ping", response_class=PlainTextResponse)
async def health_check():
    """Simple health-check endpoint compatible with the Node backend."""
    return "pong"


@app.get("/", response_class=PlainTextResponse)
async def root():
    """Root endpoint — useful for HuggingFace Spaces health probes."""
    return "Image Compressor Pro API is running"


@app.post("/api/process-stream")
async def process_stream(
    request: Request,
    quality: int = Query(default=80, ge=1, le=100),
    format: str = Query(default="jpeg", pattern="^(jpeg|png|webp|avif|heif|tiff|gif|bmp|ico|jp2)$"),
):
    """
    Receive a raw image in the request body (Content-Type: image/*),
    compress it using Pillow, and stream the result back.

    Query parameters
    ----------------
    quality : int (1–100)
        Compression quality. Higher = better quality, larger file.
    format : str
        Target output format (jpeg, png, webp, avif, heif, tiff).

    This mirrors the Node.js backend's ``POST /api/process-stream`` contract
    so the frontend works without changes.
    """
    # ---- Read the incoming image bytes (with size guard) ----
    body = await request.body()
    if len(body) == 0:
        raise HTTPException(status_code=400, detail="Empty request body")
    if len(body) > MAX_FILE_SIZE:
        raise HTTPException(
            status_code=413,
            detail=f"File too large ({len(body)} bytes). Max is {MAX_FILE_SIZE} bytes.",
        )

    # ---- Check HEIF/AVIF availability ----
    if format in ("avif", "heif") and not HEIF_AVAILABLE:
        raise HTTPException(
            status_code=400,
            detail=f"{format.upper()} format requires pillow-heif which is not installed.",
        )

    # ---- Offload CPU-bound compression to thread pool ----
    try:
        compressed = await run_in_threadpool(_compress_image, body, quality, format)
    except ValueError as e:
        raise HTTPException(status_code=400, detail=str(e))
    except Exception as e:
        log.exception("Compression failed")
        raise HTTPException(status_code=500, detail=f"Compression error: {e}")

    # ---- Stream result back ----
    mime = MIME_MAP.get(format, "application/octet-stream")

    return StreamingResponse(
        io.BytesIO(compressed),
        media_type=mime,
        headers={
            "Content-Disposition": f"attachment; filename=compressed_image.{format}",
            "Content-Length": str(len(compressed)),
            "X-Original-Size": str(len(body)),
            "X-Compressed-Size": str(len(compressed)),
        },
    )


# ---------------------------------------------------------------------------
# Entry point for local development
# ---------------------------------------------------------------------------
if __name__ == "__main__":
    import uvicorn

    uvicorn.run(
        "app:app",
        host="0.0.0.0",
        port=7860,
        workers=1,           # single worker for local dev; increase for prod
        log_level="info",
        reload=True,         # auto-reload on code changes during dev
    )