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"""Screen capture using mss — fast, cross-platform screenshots. |
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Usage: |
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from src.services.ocr.screen_capture import ScreenCapture |
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capture = ScreenCapture() |
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img = capture.grab_primary() # full primary monitor |
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img = capture.grab_region(100, 200, 800, 600) # x, y, w, h |
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""" |
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from __future__ import annotations |
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import mss |
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from PIL import Image |
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class ScreenCapture: |
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"""Fast screen capture using mss library. |
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Why per-call mss.mss(): mss uses thread-local GDI device contexts (srcdc) |
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on Windows. When created in one thread and used from another (e.g. pywebview |
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API call thread), it raises '_thread._local' object has no attribute 'srcdc'. |
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Creating a fresh mss context per grab call is cheap and thread-safe. |
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""" |
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def __init__(self) -> None: |
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with mss.mss() as sct: |
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self._monitors = list(sct.monitors) |
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@staticmethod |
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def _grab(monitor: dict) -> Image.Image: |
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"""Thread-safe grab: creates mss context per call.""" |
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with mss.mss() as sct: |
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raw = sct.grab(monitor) |
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return Image.frombytes("RGB", raw.size, raw.bgra, "raw", "BGRX").convert("RGBA") |
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def grab_primary(self) -> Image.Image: |
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"""Capture the entire primary monitor. |
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Returns: |
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PIL Image (RGBA). |
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""" |
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return self._grab(self._monitors[1]) |
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def grab_region(self, x: int, y: int, width: int, height: int) -> Image.Image: |
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"""Capture a rectangular region of the screen. |
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Args: |
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x: Left coordinate. |
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y: Top coordinate. |
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width: Width in pixels. |
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height: Height in pixels. |
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Returns: |
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PIL Image (RGBA). |
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""" |
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region = {"left": x, "top": y, "width": width, "height": height} |
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return self._grab(region) |
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def grab_monitor(self, monitor_index: int = 1) -> Image.Image: |
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"""Capture a specific monitor. |
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Args: |
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monitor_index: 1-based monitor index (1 = primary). |
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Returns: |
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PIL Image (RGBA). |
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""" |
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if monitor_index < 1 or monitor_index >= len(self._monitors): |
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raise ValueError( |
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f"Monitor index must be 1..{len(self._monitors) - 1}, got {monitor_index}" |
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) |
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return self._grab(self._monitors[monitor_index]) |
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@property |
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def monitor_count(self) -> int: |
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"""Number of physical monitors (excluding virtual 'all' monitor).""" |
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return len(self._monitors) - 1 |
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def close(self) -> None: |
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"""No-op — mss contexts are per-call now.""" |
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pass |
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