Screen Capture

Screenshot capture functionality

Screen capture functionality for Siglent oscilloscopes.

Captures the oscilloscope's display via the SCDP (screen dump) command. Modern Siglent scopes (e.g. SDS800X HD) return a raw BMP whose length is carried in the BMP header; older/other models may return an IEEE-488.2 definite-length block. Both are handled by reading exactly the number of bytes the response declares, rather than over-reading a fixed large size (which times out and drops the connection on the modern models).

ScreenCapture

ScreenCapture(oscilloscope)

Handles screenshot capture from an oscilloscope display.

The scope returns its screen as a BMP; use get_screenshot_pil() (requires Pillow) to convert to PNG/JPEG.

Initialize screen capture.

Parameters:

Name	Type	Description	Default
oscilloscope		Parent Oscilloscope instance	required

Source code in scpi_control/screen_capture.py

def __init__(self, oscilloscope):
    """Initialize screen capture.

    Args:
        oscilloscope: Parent Oscilloscope instance
    """
    self._scope = oscilloscope

capture_screenshot

capture_screenshot(image_format: str = 'BMP') -> bytes

Capture a screenshot from the oscilloscope display via SCDP.

The SCDP command returns the screen image in the scope's native format (BMP on current Siglent models). image_format is accepted for backwards compatibility but ignored; use get_screenshot_pil() to convert.

Parameters:

Name	Type	Description	Default
image_format	str	Ignored (SCDP returns the scope's native format).	'BMP'

Returns:

Type	Description
bytes	Binary image data (BMP).

Raises:

Type	Description
RuntimeError	If capture fails.

Example

scope = Oscilloscope('192.168.1.100') scope.connect() data = scope.screen_capture.capture_screenshot() open("screenshot.bmp", "wb").write(data)

Source code in scpi_control/screen_capture.py

def capture_screenshot(self, image_format: str = "BMP") -> bytes:
    """Capture a screenshot from the oscilloscope display via SCDP.

    The SCDP command returns the screen image in the scope's native format
    (BMP on current Siglent models). ``image_format`` is accepted for
    backwards compatibility but ignored; use get_screenshot_pil() to convert.

    Args:
        image_format: Ignored (SCDP returns the scope's native format).

    Returns:
        Binary image data (BMP).

    Raises:
        RuntimeError: If capture fails.

    Example:
        >>> scope = Oscilloscope('192.168.1.100')
        >>> scope.connect()
        >>> data = scope.screen_capture.capture_screenshot()
        >>> open("screenshot.bmp", "wb").write(data)
    """
    logger.info("Capturing screenshot using SCDP command")
    try:
        image_data = self._capture_with_scdp()
        if not image_data:
            raise RuntimeError("SCDP returned empty data")
        logger.info(f"Screenshot captured successfully ({len(image_data)} bytes)")
        return image_data
    except Exception as e:
        logger.error(f"Screenshot capture failed: {e}")
        raise RuntimeError(f"Failed to capture screenshot: {e}")

save_screenshot

save_screenshot(filename: str, image_format: Optional[str] = None) -> None

Capture and save a screenshot to a file.

The SCDP command returns BMP data. If you pass a different extension (e.g. .png), the file will still contain BMP bytes -- use get_screenshot_pil() and Pillow to convert formats.

Parameters:

Name	Type	Description	Default
filename	str	Output file path (recommend a .bmp extension).	required
image_format	Optional[str]	Ignored (SCDP always returns BMP).	None

Example

scope.screen_capture.save_screenshot("capture.bmp")

To save as PNG (requires Pillow):

img = scope.screen_capture.get_screenshot_pil() img.save("capture.png", "PNG")

Source code in scpi_control/screen_capture.py

def save_screenshot(self, filename: str, image_format: Optional[str] = None) -> None:
    """Capture and save a screenshot to a file.

    The SCDP command returns BMP data. If you pass a different extension
    (e.g. .png), the file will still contain BMP bytes -- use
    get_screenshot_pil() and Pillow to convert formats.

    Args:
        filename: Output file path (recommend a .bmp extension).
        image_format: Ignored (SCDP always returns BMP).

    Example:
        >>> scope.screen_capture.save_screenshot("capture.bmp")

        To save as PNG (requires Pillow):
        >>> img = scope.screen_capture.get_screenshot_pil()
        >>> img.save("capture.png", "PNG")
    """
    image_data = self.capture_screenshot()
    with open(filename, "wb") as f:
        f.write(image_data)
    logger.info(f"Screenshot saved to {filename} (BMP format)")

get_screenshot_pil

get_screenshot_pil()

Capture a screenshot and return it as a PIL Image.

Requires Pillow. Use this to convert the BMP screen dump to other formats.

Returns:

Type	Description
	PIL.Image loaded from the captured BMP data.

Raises:

Type	Description
ImportError	If Pillow is not installed.

Example

img = scope.screen_capture.get_screenshot_pil() img.save("screenshot.png", "PNG")

Source code in scpi_control/screen_capture.py

def get_screenshot_pil(self):
    """Capture a screenshot and return it as a PIL Image.

    Requires Pillow. Use this to convert the BMP screen dump to other formats.

    Returns:
        PIL.Image loaded from the captured BMP data.

    Raises:
        ImportError: If Pillow is not installed.

    Example:
        >>> img = scope.screen_capture.get_screenshot_pil()
        >>> img.save("screenshot.png", "PNG")
    """
    try:
        from PIL import Image
    except ImportError:
        raise ImportError("PIL/Pillow is required for this function. Install with: pip install Pillow")

    image_data = self.capture_screenshot()
    return Image.open(BytesIO(image_data))

See Also

• Oscilloscope - Main oscilloscope control class for SCPI communication