ent"] = s
    self.app["COM"] = s  # compatibility
    self.applist.append(("COM", s))


def SOF(self, marker):
    #
    # Start of frame marker.  Defines the size and mode of the
    # image.  JPEG is colour blind, so we use some simple
    # heuristics to map the number of layers to an appropriate
    # mode.  Note that this could be made a bit brighter, by
    # looking for JFIF and Adobe APP markers.

    n = i16(self.fp.read(2)) - 2
    s = ImageFile._safe_read(self.fp, n)
    self._size = i16(s, 3), i16(s, 1)

    self.bits = s[0]
    if self.bits != 8:
        msg = f"cannot handle {self.bits}-bit layers"
        raise SyntaxError(msg)

    self.layers = s[5]
    if self.layers == 1:
        self._mode = "L"
    elif self.layers == 3:
        self._mode = "RGB"
    elif self.layers == 4:
        self._mode = "CMYK"
    else:
        msg = f"cannot handle {self.layers}-layer images"
        raise SyntaxError(msg)

    if marker in [0xFFC2, 0xFFC6, 0xFFCA, 0xFFCE]:
        self.info["progressive"] = self.info["progression"] = 1

    if self.icclist:
        # fixup icc profile
        self.icclist.sort()  # sort by sequence number
        if self.icclist[0][13] == len(self.icclist):
            profile = []
            for p in self.icclist:
                profile.append(p[14:])
            icc_profile = b"".join(profile)
        else:
            icc_profile = None  # wrong number of fragments
        self.info["icc_profile"] = icc_profile
        self.icclist = []

    for i in range(6, len(s), 3):
        t = s[i : i + 3]
        # 4-tuples: id, vsamp, hsamp, qtable
        self.layer.append((t[0], t[1] // 16, t[1] & 15, t[2]))


def DQT(self, marker):
    #
    # Define quantization table.  Note that there might be more
    # than one table in each marker.

    # FIXME: The quantization tables can be used to estimate the
    # compression quality.

    n = i16(self.fp.read(2)) - 2
    s = ImageFile._safe_read(self.fp, n)
    while len(s):
        v = s[0]
        precision = 1 if (v // 16 == 0) else 2  # in bytes
        qt_length = 1 + precision * 64
        if len(s) < qt_length:
            msg = "bad quantization table marker"
            raise SyntaxError(msg)
        data = array.array("B" if precision == 1 else "H", s[1:qt_length])
        if sys.byteorder == "little" and precision > 1:
            data.byteswap()  # the values are always big-endian
        self.quantization[v & 15] = [data[i] for i in zigzag_index]
        s = s[qt_length:]


#
# JPEG marker table

MARKER = {
    0xFFC0: ("SOF0", "Baseline DCT", SOF),
    0xFFC1: ("SOF1", "Extended Sequential DCT", SOF),
    0xFFC2: ("SOF2", "Progressive DCT", SOF),
    0xFFC3: ("SOF3", "Spatial lossless", SOF),
    0xFFC4: ("DHT", "Define Huffman table", Skip),
    0xFFC5: ("SOF5", "Differential sequential DCT", SOF),
    0xFFC6: ("SOF6", "Differential progressive DCT", SOF),
    0xFFC7: ("SOF7", "Differential spatial", SOF),
    0xFFC8: ("JPG", "Extension", None),
    0xFFC9: ("SOF9", "Extended sequential DCT (AC)", SOF),
    0xFFCA: ("SOF10", "Progressive DCT (AC)", SOF),
    0xFFCB: ("SOF11", "Spatial lossless DCT (AC)", SOF),
    0xFFCC: ("DAC", "Define arithmetic coding conditioning", Skip),
    0xFFCD: ("SOF13", "Differential sequential DCT (AC)", SOF),
    0xFFCE: ("SOF14", "Differential progressive DCT (AC)", SOF),
    0xFFCF: ("SOF15", "Differential spatial (AC)", SOF),
    0xFFD0: ("RST0", "Restart 0", None),
    0xFFD1: ("RST1", "Restart 1", None),
    0xFFD2: ("RST2", "Restart 2", None),
    0xFFD3: ("RST3", "Restart 3", None),
    0xFFD4: ("RST4", "Restart 4", None),
    0xFFD5: ("RST5", "Restart 5", None),
    0xFFD6: ("RST6", "Restart 6", None),
    0xFFD7: ("RST7", "Restart 7", None),
    0xFFD8: ("SOI", "Start of image", None),
    0xFFD9: ("EOI", "End of image", None),
    0xFFDA: ("SOS", "Start of scan", Skip),
    0xFFDB: ("DQT", "Define quantization table", DQT),
    0xFFDC: ("DNL", "Define number of lines", Skip),
    0xFFDD: ("DRI", "Define restart interval", Skip),
    0xFFDE: ("DHP", "Define hierarchical progression", SOF),
    0xFFDF: ("EXP", "Expand reference component", Skip),
    0xFFE0: ("APP0", "Application segment 0", APP),
    0xFFE1: ("APP1", "Application segment 1", APP),
    0xFFE2: ("APP2", "Application segment 2", APP),
    0xFFE3: ("APP3", "Application segment 3", APP),
    0xFFE4: ("APP4", "Application segment 4", APP),
    0xFFE5: ("APP5", "Application segment 5", APP),
    0xFFE6: ("APP6", "Application segment 6", APP),
    0xFFE7: ("APP7", "Application segment 7", APP),
    0xFFE8: ("APP8", "Application segment 8", APP),
    0xFFE9: ("APP9", "Application segment 9", APP),
    0xFFEA: ("APP10", "Application segment 10", APP),
    0xFFEB: ("APP11", "Application segment 11", APP),
    0xFFEC: ("APP12", "Application segment 12", APP),
    0xFFED: ("APP13", "Application segment 13", APP),
    0xFFEE: ("APP14", "Application segment 14", APP),
    0xFFEF: ("APP15", "Application segment 15", APP),
    0xFFF0: ("JPG0", "Extension 0", None),
    0xFFF1: ("JPG1", "Extension 1", None),
    0xFFF2: ("JPG2", "Extension 2", None),
    0xFFF3: ("JPG3", "Extension 3", None),
    0xFFF4: ("JPG4", "Extension 4", None),
    0xFFF5: ("JPG5", "Extension 5", None),
    0xFFF6: ("JPG6", "Extension 6", None),
    0xFFF7: ("JPG7", "Extension 7", None),
    0xFFF8: ("JPG8", "Extension 8", None),
    0xFFF9: ("JPG9", "Extension 9", None),
    0xFFFA: ("JPG10", "Extension 10", None),
    0xFFFB: ("JPG11", "Extension 11", None),
    0xFFFC: ("JPG12", "Extension 12", None),
    0xFFFD: ("JPG13", "Extension 13", None),
    0xFFFE: ("COM", "Comment", COM),
}


def _accept(prefix):
    # Magic number was taken from https://en.wikipedia.org/wiki/JPEG
    return prefix[:3] == b"\xFF\xD8\xFF"


##
# Image plugin for JPEG and JFIF images.


class JpegImageFile(ImageFile.ImageFile):
    format = "JPEG"
    format_description = "JPEG (ISO 10918)"

    def _open(self):
        s = self.fp.read(3)

        if not _accept(s):
            msg = "not a JPEG file"
            raise SyntaxError(msg)
        s = b"\xFF"

        # Create attributes
        self.bits = self.layers = 0

        # JPEG specifics (internal)
        self.layer = []
        self.huffman_dc = {}
        self.huffman_ac = {}
        self.quantization = {}
        self.app = {}  # compatibility
        self.applist = []
        self.icclist = []

        while True:
            i = s[0]
            if i == 0xFF:
                s = s + self.fp.read(1)
                i = i16(s)
            else:
                # Skip non-0xFF junk
                s = self.fp.read(1)
                continue

            if i in MARKER:
                name, description, handler = MARKER[i]
                if handler is not None:
                    handler(self, i)
                if i == 0xFFDA:  # start of scan
                    rawmode = self.mode
                    if self.mode == "CMYK":
                        rawmode = "CMYK;I"  # assume adobe conventions
                    self.tile = [("jpeg", (0, 0) + self.size, 0, (rawmode, ""))]
                    # self.__offset = self.fp.tell()
                    break
                s = self.fp.read(1)
            elif i == 0 or i == 0xFFFF:
                # padded marker or junk; move on
                s = b"\xff"
            elif i == 0xFF00:  # Skip extraneous data (escaped 0xFF)
                s = self.fp.read(1)
            else:
                msg = "no marker found"
                raise SyntaxError(msg)

    def load_read(self, read_bytes):
        """
        internal: read more image data
        For premature EOF and LOAD_TRUNCATED_IMAGES adds EOI marker
        so libjpeg can finish decoding
        """
        s = self.fp.read(read_bytes)

        if not s and ImageFile.LOAD_TRUNCATED_IMAGES and not hasattr(self, "_ended"):
            # Premature EOF.
            # Pretend file is finished adding EOI marker
            self._ended = True
            return b"\xFF\xD9"

        return s

    def draft(self, mode, size):
        if len(self.tile) != 1:
            return

        # Protect from second call
        if self.decoderconfig:
            return

        d, e, o, a = self.tile[0]
        scale = 1
        original_size = self.size

        if a[0] == "RGB" and mode in ["L", "YCbCr"]:
            self._mode = mode
            a = mode, ""

        if size:
            scale = min(self.size[0] // size[0], self.size[1] // size[1])
            for s in [8, 4, 2, 1]:
                if scale >= s:
                    break
            e = (
                e[0],
                e[1],
                (e[2] - e[0] + s - 1) // s + e[0],
                (e[3] - e[1] + s - 1) // s + e[1],
            )
            self._size = ((self.size[0] + s - 1) // s, (self.size[1] + s - 1) // s)
            scale = s

        self.tile = [(d, e, o, a)]
        self.decoderconfig = (scale, 0)

        b