怎么用Python监控NASATV直播画面
本篇内容主要讲解“怎么用 Python 监控 NASA TV 直播画面”，感兴趣的朋友不妨来看看。本文介绍的方法操作简单快捷，实用性强。下面就让小编来带大家学习“怎么用 Python 监控 NASA TV 直播画面”吧!
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本文分享一个名为"Spacestills"的开源程序，它可以用于查看 NASA TV 的直播画面（静止帧）。
演示地址：
https://replit.com/@PaoloAmoroso/spacestills
在Replit上运行的Spacestills主窗口
这是一个具有GUI的简单系统，它访问feed流并从Web下载数据。该程序仅需350行代码，并依赖于一些开源的Python库。
关于程序
Spacestills会定期从feed流中下载NASA TV静止帧并将其显示在GUI中。
该程序可以校正帧的纵横比，并将其保存为PNG格式。它会自动下载最新的帧，并提供手动重新加载，禁用自动重新加载或更改下载频率的选项。
Spacestillsis是一个比较初级的版本，但是它可以做一些有用的事情：捕获并保存NASA TV直播的太空事件图像。太空爱好者经常在社交网络或论坛共享他们从NASA TV手动获取的屏幕截图。Spacestills节省了使用屏幕捕获工具的时间，并保存了可供共享的图像文件。您可以在Replit上在线运行Spacestills。
开发环境
笔者用Replit开发了Spacestills。Replit是云上的开发，部署和协作环境，它支持包括Python在内的数十种编程语言和框架。作为Chrome操作系统和云计算爱好者，笔者非常喜欢Replit，因为它可以在浏览器中完全正常运行，无需下载或安装任何内容。
资源和依赖包
Spacestills依赖于一些外部资源和Python库。
NASA TV feed 流
肯尼迪航天中心的网站上有一个页面，其中包含精选的NASA视频流，包括NASA电视公共频道。feed流显示最新的静止帧并自动更新。
每个feed都带有三种尺寸的帧，Spacestills依赖于具有704x408像素帧的最大NASA TV feed流。最大更新频率为每45秒一次。因此，检索最新的静止帧就像从feed流的URL下载JPEG图像一样简单。
原始图像被垂直拉伸，看起来很奇怪。因此，该程序可以通过压缩图像并生成未失真的16：9版本来校正纵横比。
Python
因PySimpleGUI的原因需要安装 Python 3.6 版本。
第三方库
Pillow：图像处理
PySimpleGUI：GUI框架（Spacestills使用Tkinter后端）
Request：HTTP请求
完整代码
from io import BytesIO from datetime import datetime, timedelta from pathlib import Path import requests from requests.exceptions import Timeout from PIL import Image import PySimpleGUI as sg FEED_URL = 'https://science.ksc.nasa.gov/shuttle/countdown/video/chan2large.jpg' # Frame size without and with 16:9 aspect ratio correction WIDTH = 704 HEIGHT = 480 HEIGHT_16_9 = 396 # Minimum, default, and maximum autoreload interval in seconds MIN_DELTA = 45 DELTA = MIN_DELTA MAX_DELTA = 300 class StillFrame(): """Holds a still frame. The image is stored as a PNG PIL.Image and kept in PNG format. Attributes ---------- image : PIL.Image A still frame original : PIL.Image Original frame with wchich the instance is initialized, cached in case of resizing to the original size Methods ------- bytes : Return the raw bytes resize : Resize the screenshot new_size : Calculate new aspect ratio """ def __init__(self, image): """Convert the image to PNG and cache the converted original. Parameters ---------- image : PIL.Image Image to store """ self.image = image self._topng() selfself.original = self.image def _topng(self): """Convert image format of frame to PNG. Returns ------- StillFrame Frame with image in PNG format """ if not self.image.format == 'PNG': png_file = BytesIO() self.image.save(png_file, 'png') png_file.seek(0) png_image = Image.open(png_file) self.image = png_image return self def bytes(self): """Return raw bytes of a frame image. Returns ------- bytes Byte stream of the frame image """ file = BytesIO() self.image.save(file, 'png') file.seek(0) return file.read() def new_size(self): """Return image size toggled between original and 16:9. Returns ------- 2-tuple New size """ size = self.image.size original_size = self.original.size new_size = (WIDTH, HEIGHT_16_9) if size == original_size else (WIDTH, HEIGHT) return new_size def resize(self, new_size): """Resize frame image. Parameters ---------- new_size : 2-tuple New size Returns ------- StillFrame Frame with image resized """ if not(self.image.size == new_size): selfself.image = self.image.resize(new_size) return self def make_blank_image(size=(WIDTH, HEIGHT)): """Create a blank image with a blue background. Parameters ---------- size : 2-tuple Image size Returns ------- PIL.Image Blank image """ image = Image.new('RGB', sizesize=size, color='blue') return image def download_image(url): """Download current NASA TV image. Parameters ---------- url : str URL to download the image from Returns ------- PIL.Image Downloaded image if no errors, otherwise blank image """ try: response = requests.get(url, timeout=(0.5, 0.5)) if response.status_code == 200: image = Image.open(BytesIO(response.content)) else: image = make_blank_image() except Timeout: image = make_blank_image() return image def refresh(window, resize=False, feed=FEED_URL): """Display the latest still frame in window. Parameters ---------- window : sg.Window Window to display the still to feed : string Feed URL Returns ------- StillFrame Refreshed screenshot """ still = StillFrame(download_image(feed)) if resize: still = change_aspect_ratio(window, still, new_size=(WIDTH, HEIGHT_16_9)) else: window['-IMAGE-'].update(data=still.bytes()) return still def change_aspect_ratio(window, still, new_size=(WIDTH, HEIGHT_16_9)): """Change the aspect ratio of the still displayed in window. Parameters ---------- window : sg.Window Window containing the still new_size : 2-tuple New size of the still Returns ------- StillFrame Frame containing the resized image """ resized_still = still.resize(new_size) window['-IMAGE-'].update(data=resized_still.bytes()) return resized_still def save(still, path): """Save still to a file. Parameters ---------- still : StillFrame Still to save path : string File name Returns ------- Boolean True if file saved with no errors """ filename = Path(path) try: with open(filename, 'wb') as file: file.write(still.bytes()) saved = True except OSError: saved = False return saved def next_timeout(delta): """Return the moment in time right now + delta seconds from now. Parameters ---------- delta : int Time in seconds until the next timeout Returns ------- datetime.datetime Moment in time of the next timeout """ rightnow = datetime.now() return rightnow + timedelta(seconds=delta) def timeout_due(next_timeout): """Return True if the next timeout is due. Parameters ---------- next_timeout : datetime.datetime Returns ------- bool True if the next timeout is due """ rightnow = datetime.now() return rightnow >= next_timeout def validate_delta(value): """Check if value is an int within the proper range for a time delta. Parameters ---------- value : int Time in seconds until the next timeout Returns ------- int Time in seconds until the next timeout bool True if the argument is a valid time delta """ isinteger = False try: isinteger = type(int(value)) is int except Exception: delta = DELTA delta = int(value) if isinteger else delta isvalid = MIN_DELTA <= delta <= MAX_DELTA deltadelta = delta if isvalid else DELTA return delta, isinteger and isvalid LAYOUT = [[sg.Image(key='-IMAGE-')], [sg.Checkbox('Correct aspect ratio', key='-RESIZE-', enable_events=True), sg.Button('Reload', key='-RELOAD-'), sg.Button('Save', key='-SAVE-'), sg.Exit()], [sg.Checkbox('Auto-reload every (seconds):', key='-AUTORELOAD-', default=True), sg.Input(DELTA, key='-DELTA-', size=(3, 1), justification='right'), sg.Button('Set', key='-UPDATE_DELTA-')]] def main(layout): """Run event loop.""" window = sg.Window('Spacestills', layout, finalize=True) current_still = refresh(window) delta = DELTA next_reload_time = datetime.now() + timedelta(seconds=delta) while True: event, values = window.read(timeout=100) if event in (sg.WIN_CLOSED, 'Exit'): break elif ((event == '-RELOAD-') or (values['-AUTORELOAD-'] and timeout_due(next_reload_time))): current_still = refresh(window, values['-RESIZE-']) if values['-AUTORELOAD-']: next_reload_time = next_timeout(delta) elif event == '-RESIZE-': current_still = change_aspect_ratio( window, current_still, current_still.new_size()) elif event == '-SAVE-': filename = sg.popup_get_file( 'File name', file_types=[('PNG', '*.png')], save_as=True, title='Save image', default_extension='.png') if filename: savesaved = save(current_still, filename) if not saved: sg.popup_ok('Error while saving file:', filename, title='Error') elif event == '-UPDATE_DELTA-': # The current cycle should complete at the already scheduled time. So # don't update next_reload_time yet because it'll be taken care of at the # next -AUTORELOAD- or -RELOAD- event. delta, valid = validate_delta(values['-DELTA-']) if not valid: window['-DELTA-'].update(str(DELTA)) window.close() del window if __name__ == '__main__': main(LAYOUT)到此，相信大家对“怎么用 Python 监控 NASA TV 直播画面”有了更深的了解，不妨来实际操作一番吧！这里是创新互联网站，更多相关内容可以进入相关频道进行查询，关注我们，继续学习！
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