Add flat vision dataset size computation

It is about 8.7 GB.

datasets/vision/README.md

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+https://lesc.dinfo.unifi.it/VISION/dataset/

datasets/vision/total_size.py

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+import requests
+from lxml import html
+
+url = 'https://lesc.dinfo.unifi.it/VISION/dataset/'
+
+def getFolderEntries(url):
+    text = requests.get(url).text
+    tree = html.fromstring(text)
+    # Remove legend, deisgn and `Parent Directory` entries.
+    entriesLines = tree.xpath('//tr')[3:-1]
+    entries = []
+    for entryLine in entriesLines:
+        entryColumns = entryLine.xpath('td')
+        entryName = entryColumns[1].text_content()
+        entrySize = entryColumns[3].text_content().strip()
+        if entrySize != '-':
+            sizeUnit = entrySize[-1]
+            sizeValue = float(entrySize[:-1])
+            entrySize = int(sizeValue * {
+                'K': 1_000,
+                'M': 1_000_000,
+            }[sizeUnit])
+        entries += [[entryName, entrySize]]
+    return entries
+
+totalPhotoSizes = 0
+phoneFolders = getFolderEntries(url)
+for phoneFolder, _ in phoneFolders:
+    phoneName = phoneFolder[:-1]
+    print(phoneName)
+    phonePhotos = getFolderEntries(f'{url}/{phoneName}/images/flat/')
+    for phonePhotoName, phonePhotoSize in phonePhotos:
+        print(phonePhotoName, phonePhotoSize)
+        totalPhotoSizes += phonePhotoSize
+
+print(totalPhotoSizes)