演示地址：
https://replit.com/@PaoloAmoroso/spacestills
這是一個具有GUI的簡單系統，它訪問feed流并從Web下載數據。該程序僅需350行代碼，并依賴于一些開源的Python庫。
關于程序
Spacestills會定期從feed流中下載NASA TV靜止幀并將其顯示在GUI中。
該程序可以校正幀的縱橫比，并將其保存為PNG格式。它會自動下載最新的幀，并提供手動重新加載，禁用自動重新加載或更改下載頻率的選項。
Spacestillsis是一個比較初級的版本，但是它可以做一些有用的事情：捕獲并保存NASA TV直播的太空事件圖像。太空愛好者經常在社交網絡或論壇共享他們從NASA TV手動獲取的屏幕截圖。Spacestills節省了使用屏幕捕獲工具的時間，并保存了可供共享的圖像文件。您可以在Replit上在線運行Spacestills。
開發環境
筆者用Replit開發了Spacestills。Replit是云上的開發，部署和協作環境，它支持包括Python在內的數十種編程語言和框架。作為Chrome操作系統和云計算愛好者，筆者非常喜歡Replit，因為它可以在瀏覽器中完全正常運行，無需下載或安裝任何內容。
資源和依賴包
Spacestills依賴于一些外部資源和Python庫。
NASA TV feed 流
肯尼迪航天中心的網站上有一個頁面，其中包含精選的NASA視頻流，包括NASA電視公共頻道。feed流顯示最新的靜止幀并自動更新。
每個feed都帶有三種尺寸的幀，Spacestills依賴于具有704x408像素幀的最大NASA TV feed流。最大更新頻率為每45秒一次。因此，檢索最新的靜止幀就像從feed流的URL下載JPEG圖像一樣簡單。
原始圖像被垂直拉伸，看起來很奇怪。因此，該程序可以通過壓縮圖像并生成未失真的16：9版本來校正縱橫比。
Python
因PySimpleGUI的原因需要安裝 Python 3.6 版本。
第三方庫
- Pillow：圖像處理
- PySimpleGUI：GUI框架（Spacestills使用Tkinter后端）
- Request：HTTP請求
完整代碼
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from io import BytesIOfrom datetime import datetime, timedeltafrom pathlib import Pathimport requestsfrom requests.exceptions import Timeoutfrom PIL import Imageimport PySimpleGUI as sgFEED_URL = 'https://science.ksc.nasa.gov/shuttle/countdown/video/chan2large.jpg'# Frame size without and with 16:9 aspect ratio correctionWIDTH = 704HEIGHT = 480HEIGHT_16_9 = 396# Minimum, default, and maximum autoreload interval in secondsMIN_DELTA = 45DELTA = MIN_DELTAMAX_DELTA = 300class 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() self.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): self.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', size=size, color='blue') return imagedef 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 imagedef 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 stilldef 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_stilldef 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 saveddef 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_timeoutdef 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 delta = delta if isvalid else DELTA return delta, isinteger and isvalidLAYOUT = [[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: saved = 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 windowif __name__ == '__main__': main(LAYOUT) |
以上就是用 Python 監控 NASA TV 直播畫面的實現步驟的詳細內容，更多關于Python 監控 NASA TV 直播畫面的資料請關注服務器之家其它相關文章！
原文鏈接：https://mp.weixin.qq.com/s/E6zS1tMHEq_cA5rELh1F0A
