pipeable "file" command replacement for gif/jpeg/png (https://www.raspberrypi.org/forums/viewtopic.php?f=32&t=262967)

img_type_size.py

#!/usr/bin/env python3
'''
Pipeable "file" command replacement for gif/jpeg/png images.

Outputs three lines (type, width, height), followed by copy of input.
'''
import struct
import sys

def get_image_type_size(fhandle):
    '''Determine the image type of fhandle and return its size.
    from draco / Fred the Fantastic / Dagh Bunnstad;
    imghdr removed and pipe handling added by HermannSW'''
    not_ok = False, False, False, False
    read_sofar = bytearray()
    head = fhandle.peek(24)
    if len(head) < 24:
        return not_ok
    if head[:4] == b'\x89\x50\x4e\x47':
        check = struct.unpack('>i', head[4:8])[0]
        if check != 0x0d0a1a0a:
            return not_ok
        width, height = struct.unpack('>ii', head[16:24])
        itype = "png"
    elif head[:4] == b'\x47\x49\x46\x38':
        width, height = struct.unpack('<HH', head[6:10])
        itype = "gif"
    elif head[:2] == b'\xff\xd8':
        try:
            # Because of .peek(24) above, no .seek(0) needed. Read 0xff next
            size = 2
            ftype = 0
            while not 0xc0 <= ftype <= 0xcf or ftype in (0xc4, 0xc8, 0xcc):
                read_sofar += fhandle.read(size+1)
                while read_sofar[-1] == 0xff:
                    read_sofar += fhandle.read(1)
                ftype = read_sofar[-1]
                read_sofar += fhandle.read(2)
                size = struct.unpack('>H', read_sofar[-2:])[0] - 2
            # We are at a SOFn block
            read_sofar += fhandle.read(1+4)   # Skip `precision' byte.
            height, width = struct.unpack('>HH', read_sofar[-4:])
            itype = "jpeg"
        except Exception: #IGNORE:W0703
            return not_ok
    else:
        return not_ok

    return itype, width, height, read_sofar


FROM_FILE = len(sys.argv) > 1 and sys.argv[1] != '-'
FHANDLE = open(sys.argv[1], 'rb') if FROM_FILE else sys.stdin.buffer
RET = get_image_type_size(FHANDLE)
if not RET[0]:
    sys.exit()
print(str(RET[0])+'\n'+str(RET[1])+'\n'+str(RET[2]))
sys.stdout.flush()

# sys.exit()

sys.stdout.buffer.write(RET[3])
while True:
    BUF = FHANDLE.read(1024)
    if BUF:
        sys.stdout.buffer.write(BUF)
    else:
        break