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# Copyright (C) 2024 Intel Corporation
# SPDX-License-Identifier: Apache-2.0
#
"""Streamer for reading input."""
from __future__ import annotations
import abc
import contextlib
import multiprocessing
import os
import queue
import sys
from enum import Enum
from pathlib import Path
from typing import TYPE_CHECKING, Iterator
if TYPE_CHECKING:
import numpy as np
import cv2
class MediaType(Enum):
"""This Enum represents the types of input."""
IMAGE = 1
DIR = 2
VIDEO = 3
CAMERA = 4
class BaseStreamer(metaclass=abc.ABCMeta):
"""Base Streamer interface to implement Image, Video and Camera streamers."""
@abc.abstractmethod
def __init__(self, input_path: str, loop: bool = False) -> None:
"""Initialize the streamer object.
Args:
input_path (str): path to the input stream
loop (bool, optional): whether to loop the stream or not. Defaults to False.
"""
raise NotImplementedError
@abc.abstractmethod
def __iter__(self) -> Iterator[np.ndarray]:
"""Iterate through the streamer object that is a Python Generator object.
Returns:
np.ndarray: Yield the image or video frame.
"""
raise NotImplementedError
@abc.abstractmethod
def get_type(self) -> MediaType:
"""Get type of streamer.
Returns:
MediaType: type of streamer.
"""
raise NotImplementedError
def fps(self) -> float:
"""Returns a frequency of getting images from source."""
raise NotImplementedError
def _process_run(streamer: BaseStreamer, buffer: multiprocessing.Queue) -> None:
"""Private function that is run by the thread.
Waits for the buffer to gain space for timeout seconds while it is full.
If no space was available within this time the function will exit
streamer (BaseStreamer): The streamer to retrieve frames from
buffer (multiprocessing.Queue): The buffer to place the retrieved frames in
"""
for frame in streamer:
buffer.put(frame)
class ThreadedStreamer(BaseStreamer):
"""Runs a BaseStreamer on a separate thread.
streamer (BaseStreamer): The streamer to run on a thread
buffer_size (int): Number of frame to buffer internally. Defaults to 2.
Example:
>>> streamer = VideoStreamer(path="../demo.mp4")
>>> threaded_streamer = ThreadedStreamer(streamer)
>>> for frame in threaded_streamer:
... pass
"""
def __init__(self, streamer: BaseStreamer, buffer_size: int = 2) -> None:
self.buffer_size = buffer_size
self.streamer = streamer
def __iter__(self) -> Iterator[np.ndarray]:
"""Get frames from streamer and yield them.
Yields:
Iterator[np.ndarray]: Yield the image or video frame.
"""
buffer: multiprocessing.Queue = multiprocessing.Queue(maxsize=self.buffer_size)
process = multiprocessing.Process(target=_process_run, args=(self.streamer, buffer))
# Make thread a daemon so that it will exit when the main program exits as well
process.daemon = True
process.start()
try:
with contextlib.suppress(queue.Empty):
while process.is_alive() or not buffer.empty():
yield buffer.get(timeout=0.1)
except GeneratorExit:
process.terminate()
finally:
process.join(timeout=0.1)
# The kill() function is only available in Python 3.7.
# Skip it if running an older Python version.
if sys.version_info >= (3, 7) and process.exitcode is None:
process.kill()
def get_type(self) -> MediaType:
"""Get type of internal streamer.
Returns:
MediaType: type of internal streamer.
"""
return self.streamer.get_type()
class VideoStreamer(BaseStreamer):
"""Video Streamer.
Args:
path: Path to the video file.
Example:
>>> streamer = VideoStreamer(path="../demo.mp4")
... for frame in streamer:
... pass
"""
def __init__(self, input_path: str, loop: bool = False) -> None:
self.media_type = MediaType.VIDEO
self.loop = loop
self.cap = cv2.VideoCapture()
status = self.cap.open(input_path)
if not status:
msg = f"Can't open the video from {input_path}"
raise RuntimeError(msg)
def __iter__(self) -> Iterator[np.ndarray]:
"""Iterates over frames of the video.
If self.loop is set to True, the video will loop infinitely.
"""
while True:
status, image = self.cap.read()
if status:
yield cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
elif self.loop:
self.cap.set(cv2.CAP_PROP_POS_FRAMES, 0)
else:
break
def fps(self) -> float:
"""Returns a frequency of getting images from source."""
return self.cap.get(cv2.CAP_PROP_FPS)
def get_type(self) -> MediaType:
"""Returns the type of media."""
return MediaType.VIDEO
class CameraStreamer(BaseStreamer):
"""Stream video frames from camera.
Args:
camera_device (int): Camera device index e.g, 0, 1
Example:
>>> streamer = CameraStreamer(camera_device=0)
... for frame in streamer:
... cv2.imshow("Window", frame)
... if ord("q") == cv2.waitKey(1):
... break
"""
def __init__(self, camera_device: str = "0") -> None:
self.media_type = MediaType.CAMERA
try:
self.stream = cv2.VideoCapture(int(camera_device))
except ValueError as err:
msg = f"Can't find the camera {camera_device}"
raise ValueError(msg) from err
def __iter__(self) -> Iterator[np.ndarray]:
"""Read video and yield the frame.
Args:
stream: Video stream captured via OpenCV's VideoCapture
Returns:
Individual frame
"""
while True:
frame_available, frame = self.stream.read()
if not frame_available:
break
frame = cv2.cvtColor(frame, cv2.COLOR_BGR2RGB)
yield frame
self.stream.release()
def get_type(self) -> MediaType:
"""Returns the type of media."""
return MediaType.CAMERA
class ImageStreamer(BaseStreamer):
"""Stream from image file.
Args:
input_path (str): Path to an image.
loop (bool): Whether to loop through the image or not. Defaults to False.
Example:
>>> streamer = ImageStreamer(path="../images")
... for frame in streamer:
... cv2.imshow("Window", frame)
... cv2.waitKey(0)
"""
def __init__(self, input_path: str, loop: bool = False) -> None:
self.loop = loop
self.media_type = MediaType.IMAGE
if not Path(input_path).is_file():
msg = f"Can't find the image by {input_path}"
raise RuntimeError(msg)
self.image = cv2.imread(input_path, cv2.IMREAD_COLOR)
if self.image is None:
msg = f"Can't open the image from {input_path}"
raise RuntimeError(msg)
self.image = cv2.cvtColor(self.image, cv2.COLOR_BGR2RGB)
def __iter__(self) -> Iterator[np.ndarray]:
"""If loop is True, yield the image again and again."""
if not self.loop:
yield self.image
else:
while True:
yield self.image
def get_type(self) -> MediaType:
"""Returns the type of the streamer."""
return MediaType.IMAGE
class DirStreamer(BaseStreamer):
"""Stream from directory of images.
Args:
path: Path to directory.
Example:
>>> streamer = DirStreamer(path="../images")
... for frame in streamer:
... cv2.imshow("Window", frame)
... cv2.waitKey(0)
"""
def __init__(self, input_path: str, loop: bool = False) -> None:
self.loop = loop
self.media_type = MediaType.DIR
self.dir = Path(input_path)
if not self.dir.is_dir():
msg = f"Can't find the dir by {input_path}"
raise RuntimeError(msg)
self.names = sorted(os.listdir(self.dir))
if not self.names:
msg = f"The dir {input_path} is empty"
raise RuntimeError(msg)
self.file_id = 0
for name in self.names:
filename = self.dir / name
image = cv2.imread(str(filename), cv2.IMREAD_COLOR)
if image is not None:
return
msg = f"Can't read the first image from {input_path}"
raise RuntimeError(msg)
def __iter__(self) -> Iterator[np.ndarray]:
"""Iterates over the images in a directory.
If self.loop is True, it reiterates again from the first image in the directory.
"""
while self.file_id < len(self.names):
filename = self.dir / self.names[self.file_id]
image = cv2.imread(str(filename), cv2.IMREAD_COLOR)
if self.file_id < len(self.names) - 1:
self.file_id = self.file_id + 1
else:
self.file_id = self.file_id + 1 if not self.loop else 0
if image is not None:
yield cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
def get_type(self) -> MediaType:
"""Returns the type of the streamer."""
return MediaType.DIR
def get_streamer(
input_stream: str,
loop: bool = False,
threaded: bool = False,
) -> BaseStreamer:
"""Get streamer object based on the file path or camera device index provided.
Args:
input_stream (str): Path to file or directory or index for camera.
loop (bool): Enable reading the input in a loop. Defaults to False.
threaded (bool): Run streaming on a separate thread. Threaded streaming option. Defaults to False.
Returns:
BaseStreamer: Streamer object.
"""
errors: list[Exception] = []
streamer_types = (ImageStreamer, DirStreamer, VideoStreamer)
for reader in streamer_types:
try:
streamer = reader(input_stream, loop) # type: ignore [abstract]
return ThreadedStreamer(streamer) if threaded else streamer
except RuntimeError as error: # noqa: PERF203
errors.append(error)
try:
streamer = CameraStreamer(input_stream)
return ThreadedStreamer(streamer) if threaded else streamer
except RuntimeError as error:
errors.append(error)
if errors:
raise RuntimeError(errors)
sys.exit(1)
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