SickGear/lib/hachoir_py3/parser/image/jpeg.py

"""
JPEG picture parser.

Information:

- APP14 documents
  http://partners.adobe.com/public/developer/en/ps/sdk/5116.DCT_Filter.pdf
  http://java.sun.com/j2se/1.5.0/docs/api/javax/imageio/metadata/doc-files/jpeg_metadata.html#color
- APP12:
  http://search.cpan.org/~exiftool/Image-ExifTool/lib/Image/ExifTool/TagNames.pod
- JPEG Data Format
  http://www.w3.org/Graphics/JPEG/itu-t81.pdf

Author: Victor Stinner, Robert Xiao
"""

from hachoir_py3.parser import Parser
from hachoir_py3.field import (FieldSet, ParserError, FieldError,
                               UInt8, UInt16, Enum, Field,
                               Bit, Bits, NullBits, NullBytes, PaddingBits,
                               String, RawBytes)
from hachoir_py3.parser.image.common import PaletteRGB
from hachoir_py3.core.endian import BIG_ENDIAN
from hachoir_py3.core.text_handler import textHandler, hexadecimal
from hachoir_py3.parser.image.exif import Exif
from hachoir_py3.parser.image.photoshop_metadata import PhotoshopMetadata
from hachoir_py3.parser.archive.zlib import build_tree
from hachoir_py3.core.tools import paddingSize, alignValue

MAX_FILESIZE = 100 * 1024 * 1024

# The four tables (hash/sum for color/grayscale JPEG) comes
# from ImageMagick project
QUALITY_HASH_COLOR = (
    1020, 1015, 932, 848, 780, 735, 702, 679, 660, 645,
    632, 623, 613, 607, 600, 594, 589, 585, 581, 571,
    555, 542, 529, 514, 494, 474, 457, 439, 424, 410,
    397, 386, 373, 364, 351, 341, 334, 324, 317, 309,
    299, 294, 287, 279, 274, 267, 262, 257, 251, 247,
    243, 237, 232, 227, 222, 217, 213, 207, 202, 198,
    192, 188, 183, 177, 173, 168, 163, 157, 153, 148,
    143, 139, 132, 128, 125, 119, 115, 108, 104, 99,
    94, 90, 84, 79, 74, 70, 64, 59, 55, 49,
    45, 40, 34, 30, 25, 20, 15, 11, 6, 4,
    0)

QUALITY_SUM_COLOR = (
    32640, 32635, 32266, 31495, 30665, 29804, 29146, 28599, 28104, 27670,
    27225, 26725, 26210, 25716, 25240, 24789, 24373, 23946, 23572, 22846,
    21801, 20842, 19949, 19121, 18386, 17651, 16998, 16349, 15800, 15247,
    14783, 14321, 13859, 13535, 13081, 12702, 12423, 12056, 11779, 11513,
    11135, 10955, 10676, 10392, 10208, 9928, 9747, 9564, 9369, 9193,
    9017, 8822, 8639, 8458, 8270, 8084, 7896, 7710, 7527, 7347,
    7156, 6977, 6788, 6607, 6422, 6236, 6054, 5867, 5684, 5495,
    5305, 5128, 4945, 4751, 4638, 4442, 4248, 4065, 3888, 3698,
    3509, 3326, 3139, 2957, 2775, 2586, 2405, 2216, 2037, 1846,
    1666, 1483, 1297, 1109, 927, 735, 554, 375, 201, 128,
    0)

QUALITY_HASH_GRAY = (
    510, 505, 422, 380, 355, 338, 326, 318, 311, 305,
    300, 297, 293, 291, 288, 286, 284, 283, 281, 280,
    279, 278, 277, 273, 262, 251, 243, 233, 225, 218,
    211, 205, 198, 193, 186, 181, 177, 172, 168, 164,
    158, 156, 152, 148, 145, 142, 139, 136, 133, 131,
    129, 126, 123, 120, 118, 115, 113, 110, 107, 105,
    102, 100, 97, 94, 92, 89, 87, 83, 81, 79,
    76, 74, 70, 68, 66, 63, 61, 57, 55, 52,
    50, 48, 44, 42, 39, 37, 34, 31, 29, 26,
    24, 21, 18, 16, 13, 11, 8, 6, 3, 2,
    0)

QUALITY_SUM_GRAY = (
    16320, 16315, 15946, 15277, 14655, 14073, 13623, 13230, 12859, 12560,
    12240, 11861, 11456, 11081, 10714, 10360, 10027, 9679, 9368, 9056,
    8680, 8331, 7995, 7668, 7376, 7084, 6823, 6562, 6345, 6125,
    5939, 5756, 5571, 5421, 5240, 5086, 4976, 4829, 4719, 4616,
    4463, 4393, 4280, 4166, 4092, 3980, 3909, 3835, 3755, 3688,
    3621, 3541, 3467, 3396, 3323, 3247, 3170, 3096, 3021, 2952,
    2874, 2804, 2727, 2657, 2583, 2509, 2437, 2362, 2290, 2211,
    2136, 2068, 1996, 1915, 1858, 1773, 1692, 1620, 1552, 1477,
    1398, 1326, 1251, 1179, 1109, 1031, 961, 884, 814, 736,
    667, 592, 518, 441, 369, 292, 221, 151, 86, 64,
    0)

JPEG_NATURAL_ORDER = (
    0, 1, 8, 16, 9, 2, 3, 10,
    17, 24, 32, 25, 18, 11, 4, 5,
    12, 19, 26, 33, 40, 48, 41, 34,
    27, 20, 13, 6, 7, 14, 21, 28,
    35, 42, 49, 56, 57, 50, 43, 36,
    29, 22, 15, 23, 30, 37, 44, 51,
    58, 59, 52, 45, 38, 31, 39, 46,
    53, 60, 61, 54, 47, 55, 62, 63)


class JpegChunkApp0(FieldSet):
    UNIT_NAME = {
        0: "pixels",
        1: "dots per inch",
        2: "dots per cm",
    }

    def createFields(self):
        yield String(self, "jfif", 5, "JFIF string", charset="ASCII")
        if self["jfif"].value != "JFIF\0":
            raise ParserError(
                "Stream doesn't look like JPEG chunk (wrong JFIF signature)")
        yield UInt8(self, "ver_maj", "Major version")
        yield UInt8(self, "ver_min", "Minor version")
        yield Enum(UInt8(self, "units", "Units"), self.UNIT_NAME)
        if self["units"].value == 0:
            yield UInt16(self, "aspect_x", "Aspect ratio (X)")
            yield UInt16(self, "aspect_y", "Aspect ratio (Y)")
        else:
            yield UInt16(self, "x_density", "X density")
            yield UInt16(self, "y_density", "Y density")
        yield UInt8(self, "thumb_w", "Thumbnail width")
        yield UInt8(self, "thumb_h", "Thumbnail height")
        thumb_size = self["thumb_w"].value * self["thumb_h"].value
        if thumb_size != 0:
            yield PaletteRGB(self, "thumb_palette", 256)
            yield RawBytes(self, "thumb_data", thumb_size, "Thumbnail data")


class Ducky(FieldSet):
    BLOCK_TYPE = {
        0: "end",
        1: "Quality",
        2: "Comment",
        3: "Copyright",
    }

    def createFields(self):
        yield Enum(UInt16(self, "type"), self.BLOCK_TYPE)
        if self["type"].value == 0:
            return
        yield UInt16(self, "size")
        size = self["size"].value
        if size:
            yield RawBytes(self, "data", size)


class APP12(FieldSet):
    """
    The JPEG APP12 "Picture Info" segment was used by some older cameras, and
    contains ASCII-based meta information.
    """

    def createFields(self):
        yield String(self, "ducky", 5, '"Ducky" string', charset="ASCII")
        while not self.eof:
            yield Ducky(self, "item[]")


class SOFComponent(FieldSet):

    def createFields(self):
        yield UInt8(self, "component_id")
        yield Bits(self, "horiz_sample", 4, "Horizontal sampling factor")
        yield Bits(self, "vert_sample", 4, "Vertical sampling factor")
        yield UInt8(self, "quant_table", "Quantization table destination selector")


class StartOfFrame(FieldSet):

    def createFields(self):
        yield UInt8(self, "precision")

        yield UInt16(self, "height")
        yield UInt16(self, "width")
        yield UInt8(self, "nr_components")

        for index in range(self["nr_components"].value):
            yield SOFComponent(self, "component[]")


class Comment(FieldSet):

    def createFields(self):
        yield String(self, "comment", self.size // 8, strip="\0")


class AdobeChunk(FieldSet):
    COLORSPACE_TRANSFORMATION = {
        1: "YCbCr (converted from RGB)",
        2: "YCCK (converted from CMYK)",
    }

    def createFields(self):
        if self.stream.readBytes(self.absolute_address, 5) != b"Adobe":
            yield RawBytes(self, "raw", self.size // 8, "Raw data")
            return
        yield String(self, "adobe", 5, "\"Adobe\" string", charset="ASCII")
        yield UInt16(self, "version", "DCT encoder version")
        yield Enum(Bit(self, "flag00"),
                   {False: "Chop down or subsampling", True: "Blend"})
        yield NullBits(self, "flags0_reserved", 15)
        yield NullBytes(self, "flags1", 2)
        yield Enum(UInt8(self, "color_transform", "Colorspace transformation code"), self.COLORSPACE_TRANSFORMATION)


class SOSComponent(FieldSet):

    def createFields(self):
        comp_id = UInt8(self, "component_id")
        yield comp_id
        if not(1 <= comp_id.value <= self["../nr_components"].value):
            raise ParserError("JPEG error: Invalid component-id")
        yield Bits(self, "dc_coding_table", 4, "DC entropy coding table destination selector")
        yield Bits(self, "ac_coding_table", 4, "AC entropy coding table destination selector")


class StartOfScan(FieldSet):

    def createFields(self):
        yield UInt8(self, "nr_components")

        for index in range(self["nr_components"].value):
            yield SOSComponent(self, "component[]")
        yield UInt8(self, "spectral_start", "Start of spectral or predictor selection")
        yield UInt8(self, "spectral_end", "End of spectral selection")
        yield Bits(self, "bit_pos_high", 4, "Successive approximation bit position high")
        yield Bits(self, "bit_pos_low", 4, "Successive approximation bit position low or point transform")


class RestartInterval(FieldSet):

    def createFields(self):
        yield UInt16(self, "interval", "Restart interval")


class QuantizationTable(FieldSet):

    def createFields(self):
        # Code based on function get_dqt() (jdmarker.c from libjpeg62)
        yield Bits(self, "is_16bit", 4)
        yield Bits(self, "index", 4)
        if self["index"].value >= 4:
            raise ParserError("Invalid quantification index (%s)" %
                              self["index"].value)
        if self["is_16bit"].value:
            coeff_type = UInt16
        else:
            coeff_type = UInt8
        for index in range(64):
            natural = JPEG_NATURAL_ORDER[index]
            yield coeff_type(self, "coeff[%u]" % natural)

    def createDescription(self):
        return "Quantification table #%u" % self["index"].value


class DefineQuantizationTable(FieldSet):

    def createFields(self):
        while self.current_size < self.size:
            yield QuantizationTable(self, "qt[]")


class HuffmanTable(FieldSet):

    def createFields(self):
        # http://www.w3.org/Graphics/JPEG/itu-t81.pdf, page 40-41
        yield Enum(Bits(self, "table_class", 4, "Table class"), {
            0: "DC or Lossless Table",
            1: "AC Table"})
        yield Bits(self, "index", 4, "Huffman table destination identifier")
        for i in range(1, 17):
            yield UInt8(self, "count[%i]" % i, "Number of codes of length %i" % i)
        lengths = []
        remap = {}
        for i in range(1, 17):
            for j in range(self["count[%i]" % i].value):
                field = UInt8(self, "value[%i][%i]" % (
                    i, j), "Value of code #%i of length %i" % (j, i))
                yield field
                remap[len(lengths)] = field.value
                lengths.append(i)
        self.tree = {}
        for i, j in build_tree(lengths).items():
            self.tree[i] = remap[j]


class DefineHuffmanTable(FieldSet):

    def createFields(self):
        while self.current_size < self.size:
            yield HuffmanTable(self, "huffman_table[]")


class HuffmanCode(Field):
    """Huffman code. Uses tree parameter as the Huffman tree."""

    def __init__(self, parent, name, tree, description=""):
        Field.__init__(self, parent, name, 0, description)

        endian = self.parent.endian
        stream = self.parent.stream
        addr = self.absolute_address

        value = 0
        met_ff = False
        while (self.size, value) not in tree:
            if addr % 8 == 0:
                last_byte = stream.readBytes(addr - 8, 1)
                if last_byte == b'\xFF':
                    next_byte = stream.readBytes(addr, 1)
                    if next_byte != b'\x00':
                        raise FieldError(
                            "Unexpected byte sequence %r!" % (last_byte + next_byte))
                    addr += 8  # hack hack hack
                    met_ff = True
                    self._description = "[skipped 8 bits after 0xFF] "
            bit = stream.readBits(addr, 1, endian)
            value <<= 1
            value += bit
            self._size += 1
            addr += 1
        self.createValue = lambda: value
        self.realvalue = tree[(self.size, value)]
        if met_ff:
            self._size += 8


class JpegHuffmanImageUnit(FieldSet):
    """8x8 block of sample/coefficient values"""

    def __init__(self, parent, name, dc_tree, ac_tree, *args, **kwargs):
        FieldSet.__init__(self, parent, name, *args, **kwargs)
        self.dc_tree = dc_tree
        self.ac_tree = ac_tree

    def createFields(self):
        field = HuffmanCode(self, "dc_data", self.dc_tree)
        field._description = "DC Code %i (Huffman Code %i)" % (
            field.realvalue, field.value) + field._description
        yield field
        if field.realvalue != 0:
            extra = Bits(self, "dc_data_extra", field.realvalue)
            if extra.value < 2**(field.realvalue - 1):
                corrected_value = extra.value + (-1 << field.realvalue) + 1
            else:
                corrected_value = extra.value
            extra._description = "Extra Bits: Corrected DC Value %i" % corrected_value
            yield extra
        data = []
        while len(data) < 63:
            field = HuffmanCode(self, "ac_data[]", self.ac_tree)
            value_r = field.realvalue >> 4
            if value_r:
                data += [0] * value_r
            value_s = field.realvalue & 0x0F
            if value_r == value_s == 0:
                field._description = "AC Code Block Terminator (0, 0) (Huffman Code %i)" % field.value + \
                    field._description
                yield field
                return
            field._description = "AC Code %i, %i (Huffman Code %i)" % (
                value_r, value_s, field.value) + field._description
            yield field
            if value_s != 0:
                extra = Bits(self, "ac_data_extra[%s" %
                             field.name.split('[')[1], value_s)
                if extra.value < 2**(value_s - 1):
                    corrected_value = extra.value + (-1 << value_s) + 1
                else:
                    corrected_value = extra.value
                extra._description = "Extra Bits: Corrected AC Value %i" % corrected_value
                data.append(corrected_value)
                yield extra
            else:
                data.append(0)


class JpegImageData(FieldSet):

    def __init__(self, parent, name, frame, scan, restart_interval, restart_offset=0, *args, **kwargs):
        FieldSet.__init__(self, parent, name, *args, **kwargs)
        self.frame = frame
        self.scan = scan
        self.restart_interval = restart_interval
        self.restart_offset = restart_offset
        # try to figure out where this field ends
        start = self.absolute_address
        while True:
            end = self.stream.searchBytes(b"\xff", start, MAX_FILESIZE * 8)
            if end is None:
                # this is a bad sign, since it means there is no terminator
                # we ignore this; it likely means a truncated image
                break
            if self.stream.readBytes(end, 2) == b'\xff\x00':
                # padding: false alarm
                start = end + 16
                continue
            else:
                self._size = end - self.absolute_address
                break

    def createFields(self):
        if self.frame["../type"].value in [0xC0, 0xC1]:
            # yay, huffman coding!
            if not hasattr(self, "huffman_tables"):
                self.huffman_tables = {}
                for huffman in self.parent.array("huffman"):
                    for table in huffman["content"].array("huffman_table"):
                        for _dummy_ in table:
                            # exhaust table, so the huffman tree is built
                            pass
                        self.huffman_tables[table["table_class"].value, table[
                            "index"].value] = table.tree
            components = []  # sos_comp, samples
            max_vert = 0
            max_horiz = 0
            for component in self.scan.array("component"):
                for sof_comp in self.frame.array("component"):
                    if sof_comp["component_id"].value == component["component_id"].value:
                        vert = sof_comp["vert_sample"].value
                        horiz = sof_comp["horiz_sample"].value
                        components.append((component, vert * horiz))
                        max_vert = max(max_vert, vert)
                        max_horiz = max(max_horiz, horiz)
            mcu_height = alignValue(
                self.frame["height"].value, 8 * max_vert) // (8 * max_vert)
            mcu_width = alignValue(
                self.frame["width"].value, 8 * max_horiz) // (8 * max_horiz)
            if self.restart_interval and self.restart_offset > 0:
                mcu_number = self.restart_interval * self.restart_offset
            else:
                mcu_number = 0
            initial_mcu = mcu_number
            while True:
                if (self.restart_interval and mcu_number != initial_mcu and mcu_number % self.restart_interval == 0) or\
                   mcu_number == mcu_height * mcu_width:
                    padding = paddingSize(self.current_size, 8)
                    if padding:
                        yield PaddingBits(self, "padding[]", padding)  # all 1s
                    last_byte = self.stream.readBytes(
                        self.absolute_address + self.current_size - 8, 1)
                    if last_byte == b'\xFF':
                        next_byte = self.stream.readBytes(
                            self.absolute_address + self.current_size, 1)
                        if next_byte != b'\x00':
                            raise FieldError(
                                "Unexpected byte sequence %r!" % (last_byte + next_byte))
                        yield NullBytes(self, "stuffed_byte[]", 1)
                    break
                for sos_comp, num_units in components:
                    for interleave_count in range(num_units):
                        yield JpegHuffmanImageUnit(self, "block[%i]component[%i][]" % (mcu_number, sos_comp["component_id"].value),
                                                   self.huffman_tables[
                                                       0, sos_comp["dc_coding_table"].value],
                                                   self.huffman_tables[1, sos_comp["ac_coding_table"].value])
                mcu_number += 1
        else:
            self.warning(
                "Sorry, only supporting Baseline & Extended Sequential JPEG images so far!")
            return


class JpegChunk(FieldSet):
    TAG_SOI = 0xD8
    TAG_EOI = 0xD9
    TAG_SOS = 0xDA
    TAG_DQT = 0xDB
    TAG_DRI = 0xDD
    TAG_INFO = {
        0xC4: ("huffman[]", "Define Huffman Table (DHT)", DefineHuffmanTable),
        0xD8: ("start_image", "Start of image (SOI)", None),
        0xD9: ("end_image", "End of image (EOI)", None),
        0xD0: ("restart_marker_0[]", "Restart Marker (RST0)", None),
        0xD1: ("restart_marker_1[]", "Restart Marker (RST1)", None),
        0xD2: ("restart_marker_2[]", "Restart Marker (RST2)", None),
        0xD3: ("restart_marker_3[]", "Restart Marker (RST3)", None),
        0xD4: ("restart_marker_4[]", "Restart Marker (RST4)", None),
        0xD5: ("restart_marker_5[]", "Restart Marker (RST5)", None),
        0xD6: ("restart_marker_6[]", "Restart Marker (RST6)", None),
        0xD7: ("restart_marker_7[]", "Restart Marker (RST7)", None),
        0xDA: ("start_scan[]", "Start Of Scan (SOS)", StartOfScan),
        0xDB: ("quantization[]", "Define Quantization Table (DQT)", DefineQuantizationTable),
        0xDC: ("nb_line", "Define number of Lines (DNL)", None),
        0xDD: ("restart_interval", "Define Restart Interval (DRI)", RestartInterval),
        0xE0: ("app0", "APP0", JpegChunkApp0),
        0xE1: ("exif", "Exif metadata", Exif),
        0xE2: ("icc", "ICC profile", None),
        0xEC: ("app12", "APP12", APP12),
        0xED: ("photoshop", "Photoshop", PhotoshopMetadata),
        0xEE: ("adobe", "Image encoding information for DCT filters (Adobe)", AdobeChunk),
        0xFE: ("comment[]", "Comment", Comment),
    }
    START_OF_FRAME = {
        0xC0: "Baseline",
        0xC1: "Extended sequential",
        0xC2: "Progressive",
        0xC3: "Lossless",
        0xC5: "Differential sequential",
        0xC6: "Differential progressive",
        0xC7: "Differential lossless",
        0xC9: "Extended sequential, arithmetic coding",
        0xCA: "Progressive, arithmetic coding",
        0xCB: "Lossless, arithmetic coding",
        0xCD: "Differential sequential, arithmetic coding",
        0xCE: "Differential progressive, arithmetic coding",
        0xCF: "Differential lossless, arithmetic coding",
    }
    for key, text in START_OF_FRAME.items():
        TAG_INFO[key] = ("start_frame", "Start of frame (%s)" %
                         text.lower(), StartOfFrame)

    def __init__(self, parent, name, description=None):
        FieldSet.__init__(self, parent, name, description)
        tag = self["type"].value
        if tag == 0xE1:
            # Hack for Adobe extension: XAP metadata (as XML)
            bytes = self.stream.readBytes(self.absolute_address + 32, 6)
            if bytes == b"Exif\0\0":
                self._name = "exif"
                self._description = "EXIF"
                self._parser = Exif
            else:
                self._parser = None
        elif tag in self.TAG_INFO:
            self._name, self._description, self._parser = self.TAG_INFO[tag]
        else:
            self._parser = None

    def createFields(self):
        yield textHandler(UInt8(self, "header", "Header"), hexadecimal)
        if self["header"].value != 0xFF:
            raise ParserError("JPEG: Invalid chunk header!")
        yield textHandler(UInt8(self, "type", "Type"), hexadecimal)
        tag = self["type"].value
        # D0 - D7 inclusive are the restart markers
        if tag in [self.TAG_SOI, self.TAG_EOI] + list(range(0xD0, 0xD8)):
            return
        yield UInt16(self, "size", "Size")
        size = (self["size"].value - 2)
        if 0 < size:
            if self._parser:
                yield self._parser(self, "content", "Chunk content", size=size * 8)
            else:
                yield RawBytes(self, "data", size, "Data")

    def createDescription(self):
        return "Chunk: %s" % self["type"].display


class JpegFile(Parser):
    endian = BIG_ENDIAN
    PARSER_TAGS = {
        "id": "jpeg",
        "category": "image",
        "file_ext": ("jpg", "jpeg"),
        "mime": ("image/jpeg",),
        "magic": (
            (b"\xFF\xD8\xFF\xE0", 0),   # (Start Of Image, APP0)
            (b"\xFF\xD8\xFF\xE1", 0),   # (Start Of Image, EXIF)
            (b"\xFF\xD8\xFF\xEE", 0),   # (Start Of Image, Adobe)
        ),
        "min_size": 22 * 8,
        "description": "JPEG picture",
        "subfile": "skip",
    }

    def validate(self):
        if self.stream.readBytes(0, 2) != b"\xFF\xD8":
            return "Invalid file signature"
        try:
            for index, field in enumerate(self):
                chunk_type = field["type"].value
                if chunk_type not in JpegChunk.TAG_INFO:
                    return "Unknown chunk type: 0x%02X (chunk #%s)" % (chunk_type, index)
                if index == 2:
                    # Only check 3 fields
                    break
        except Exception:
            return "Unable to parse at least three chunks"
        return True

    def createFields(self):
        frame = None
        scan = None
        restart_interval = None
        restart_offset = 0
        while not self.eof:
            chunk = JpegChunk(self, "chunk[]")
            yield chunk
            if chunk["type"].value in JpegChunk.START_OF_FRAME:
                # SOF0 [Baseline], SOF1 [Extended Sequential]
                if chunk["type"].value not in [0xC0, 0xC1]:
                    self.warning(
                        "Only supporting Baseline & Extended Sequential JPEG images so far!")
                frame = chunk["content"]
            if chunk["type"].value == JpegChunk.TAG_SOS:
                if not frame:
                    self.warning("Missing or invalid SOF marker before SOS!")
                    continue
                scan = chunk["content"]
                # hack: scan only the fields seen so far (in _fields): don't
                # use the generator
                if "restart_interval" in self._fields:
                    restart_interval = self[
                        "restart_interval/content/interval"].value
                else:
                    restart_interval = None
                yield JpegImageData(self, "image_data[]", frame, scan, restart_interval)
            elif chunk["type"].value in range(0xD0, 0xD8):
                restart_offset += 1
                yield JpegImageData(self, "image_data[]", frame, scan, restart_interval, restart_offset)

        # TODO: is it possible to handle piped input?
        if self._size is None:
            raise NotImplementedError

        has_end = False
        size = (self._size - self.current_size) // 8
        if size:
            if 2 < size \
                    and self.stream.readBytes(self._size - 16, 2) == b"\xff\xd9":
                has_end = True
                size -= 2
            yield RawBytes(self, "data", size, "JPEG data")
        if has_end:
            yield JpegChunk(self, "chunk[]")

    def createDescription(self):
        desc = "JPEG picture"
        if "start_frame/content" in self:
            header = self["start_frame/content"]
            desc += ": %ux%u pixels" % (header["width"].value,
                                        header["height"].value)
        return desc

    def createContentSize(self):
        if "end" in self:
            return self["end"].absolute_address + self["end"].size
        if "data" in self:
            start = self["data"].absolute_address
        elif "image_data[0]" in self:
            start = self["image_data[0]"].absolute_address
        else:
            return None
        end = self.stream.searchBytes(b"\xff\xd9", start, MAX_FILESIZE * 8)
        if end is not None:
            return end + 16
        return None