Refactor code structure for improved readability and maintainability

runpod-worker/handler.py

@@ -0,0 +1,113 @@
+"""
+RunPod Serverless worker: FLUX.2 [klein] 4B instruction image editing (img2img).
+
+Replaces the old Instruct-Pix2Pix worker. FLUX.2-klein is Apache-2.0 (no HF token),
+runs on a 24 GB card (RTX 3090), and is distilled → ~6 steps, fast. It needs a
+recent torch, which also carries kernels for the newest (Blackwell) GPUs — so it
+runs on whatever card RunPod assigns.
+
+Matches the app's img2img contract (no app-code change needed):
+  {"input": {
+     "image": "<base64>",   # required (raw base64 or data: URI)
+     "prompt": "<edit instruction>",  # required
+     "strength": 0.6,       # optional — the editor's "Edit strength" slider (mapped to guidance)
+     "seed": 123            # optional
+  }}
+Returns: {"image": "<base64 PNG>"}  (or {"error": "..."}).
+
+Tuning (env): FLUX2_MODEL (default black-forest-labs/FLUX.2-klein-4B),
+FLUX2_STEPS (default 6), FLUX2_MAX_SIZE (default 1024).
+"""
+
+import base64
+import io
+import os
+
+_V = "/runpod-volume"
+if os.path.isdir(_V):
+    os.environ.setdefault("HF_HOME", os.path.join(_V, "huggingface"))
+
+import torch  # noqa: E402
+import runpod  # noqa: E402
+from PIL import Image  # noqa: E402
+from diffusers import Flux2KleinPipeline  # noqa: E402
+
+MODEL = os.environ.get("FLUX2_MODEL", "black-forest-labs/FLUX.2-klein-4B")
+STEPS = int(os.environ.get("FLUX2_STEPS", "6"))
+MAX_SIZE = int(os.environ.get("FLUX2_MAX_SIZE", "1024"))
+
+DEVICE = "cuda" if torch.cuda.is_available() else "cpu"
+_pipe = None
+
+
+def _get_pipe():
+    global _pipe
+    if _pipe is None:
+        pipe = Flux2KleinPipeline.from_pretrained(MODEL, torch_dtype=torch.bfloat16)
+        total_gb = torch.cuda.get_device_properties(0).total_memory / 1e9 if DEVICE == "cuda" else 0
+        if total_gb >= 20:
+            pipe = pipe.to("cuda")
+        else:
+            pipe.enable_model_cpu_offload()
+        pipe.set_progress_bar_config(disable=True)
+        _pipe = pipe
+    return _pipe
+
+
+def _b64_to_image(data):
+    if "," in data:
+        data = data.split(",", 1)[1]
+    return Image.open(io.BytesIO(base64.b64decode(data))).convert("RGB")
+
+
+def _image_to_b64(img):
+    buf = io.BytesIO()
+    img.save(buf, format="PNG")
+    return base64.b64encode(buf.getvalue()).decode("utf-8")
+
+
+def _fit(img):
+    w, h = img.size
+    scale = min(1.0, MAX_SIZE / max(w, h))
+    nw = max(16, (int(w * scale) // 16) * 16)
+    nh = max(16, (int(h * scale) // 16) * 16)
+    return img.resize((nw, nh), Image.LANCZOS)
+
+
+def handler(event):
+    inp = (event or {}).get("input") or {}
+    image_b64 = inp.get("image")
+    prompt = (inp.get("prompt") or "").strip()
+    if not image_b64:
+        return {"error": "Missing 'image' (base64)."}
+    if not prompt:
+        return {"error": "Missing 'prompt' (edit instruction)."}
+
+    try:
+        image = _fit(_b64_to_image(image_b64))
+        # The editor's "Edit strength" slider (0..1) maps to guidance — FLUX.2 klein
+        # likes low guidance (~1); stronger = higher.
+        guidance = 1.0
+        strength = inp.get("strength")
+        if strength is not None:
+            s = max(0.0, min(1.0, float(strength)))
+            guidance = round(1.0 + s * 3.0, 2)
+        seed = inp.get("seed")
+        generator = torch.Generator(device="cpu").manual_seed(int(seed)) if seed is not None else None
+
+        result = _get_pipe()(
+            prompt=prompt,
+            image=image,
+            height=image.height,
+            width=image.width,
+            guidance_scale=guidance,
+            num_inference_steps=STEPS,
+            generator=generator,
+        ).images[0]
+
+        return {"image": _image_to_b64(result)}
+    except Exception as exc:
+        return {"error": f"{type(exc).__name__}: {exc}"}
+
+
+runpod.serverless.start({"handler": handler})