We get the type and size of the image without downloading it entirely, using Python

There was a task to filter the database of links to images and delete large ones. As a result, a solution was found in Python, which I will share under the habrakat:



The script itself + necessary for work library ReseekFile

The beauty of the solution is that to get information about the type and size of the image (jpg, png, gif), just download the first 24 bytes of the file.
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Analysis code of these 24 bytes:

# handle GIFs if (size >= 10) and data[:6] in ('GIF87a', 'GIF89a'): # Check to see if content_type is correct content_type = 'image/gif' w, h = struct.unpack("<HH", data[6:10]) width = int(w) height = int(h) # See PNG 2. Edition spec (http://www.w3.org/TR/PNG/) # Bytes 0-7 are below, 4-byte chunk length, then 'IHDR' # and finally the 4-byte width, height elif ((size >= 24) and data.startswith('\211PNG\r\n\032\n') and (data[12:16] == 'IHDR')): content_type = 'image/png' w, h = struct.unpack(">LL", data[16:24]) width = int(w) height = int(h) # Maybe this is for an older PNG version. elif (size >= 16) and data.startswith('\211PNG\r\n\032\n'): # Check to see if we have the right content type content_type = 'image/png' w, h = struct.unpack(">LL", data[8:16]) width = int(w) height = int(h) # handle JPEGs elif (size >= 2) and data.startswith('\377\330'): content_type = 'image/jpeg' datastream.seek(0) datastream.read(2) b = datastream.read(1) try: while (b and ord(b) != 0xDA): while (ord(b) != 0xFF): b = datastream.read(1) while (ord(b) == 0xFF): b = datastream.read(1) if (ord(b) >= 0xC0 and ord(b) <= 0xC3): datastream.read(3) h, w = struct.unpack(">HH", datastream.read(4)) break else: datastream.read(int(struct.unpack(">H", datastream.read(2))[0])-2) b = datastream.read(1) width = int(w) height = int(h) except struct.error: pass except ValueError: pass 

I hope that this script will find a place for itself in the chosen habrayuser and will serve when it is necessary :)