Pillow/src/PIL/BmpImagePlugin.py

#
# The Python Imaging Library.
# $Id$
#
# BMP file handler
#
# Windows (and OS/2) native bitmap storage format.
#
# history:
# 1995-09-01 fl   Created
# 1996-04-30 fl   Added save
# 1997-08-27 fl   Fixed save of 1-bit images
# 1998-03-06 fl   Load P images as L where possible
# 1998-07-03 fl   Load P images as 1 where possible
# 1998-12-29 fl   Handle small palettes
# 2002-12-30 fl   Fixed load of 1-bit palette images
# 2003-04-21 fl   Fixed load of 1-bit monochrome images
# 2003-04-23 fl   Added limited support for BI_BITFIELDS compression
#
# Copyright (c) 1997-2003 by Secret Labs AB
# Copyright (c) 1995-2003 by Fredrik Lundh
#
# See the README file for information on usage and redistribution.
#


from . import Image, ImageFile, ImagePalette
from ._binary import i8, i16le as i16, i32le as i32, o8, o16le as o16, o32le as o32

#
# --------------------------------------------------------------------
# Read BMP file

BIT2MODE = {
    # bits => mode, rawmode
    1: ("P", "P;1"),
    4: ("P", "P;4"),
    8: ("P", "P"),
    16: ("RGB", "BGR;15"),
    24: ("RGB", "BGR"),
    32: ("RGB", "BGRX"),
}


def _accept(prefix):
    return prefix[:2] == b"BM"


def _dib_accept(prefix):
    return i32(prefix[:4]) in [12, 40, 64, 108, 124]


# =============================================================================
# Image plugin for the Windows BMP format.
# =============================================================================
class BmpImageFile(ImageFile.ImageFile):
    """ Image plugin for the Windows Bitmap format (BMP) """

    # ------------------------------------------------------------- Description
    format_description = "Windows Bitmap"
    format = "BMP"

    # -------------------------------------------------- BMP Compression values
    COMPRESSIONS = {"RAW": 0, "RLE8": 1, "RLE4": 2, "BITFIELDS": 3, "JPEG": 4, "PNG": 5}
    for k, v in COMPRESSIONS.items():
        vars()[k] = v

    def _bitmap(self, header=0, offset=0):
        """ Read relevant info about the BMP """
        read, seek = self.fp.read, self.fp.seek
        if header:
            seek(header)
        file_info = {}
        # read bmp header size @offset 14 (this is part of the header size)
        file_info["header_size"] = i32(read(4))
        file_info["direction"] = -1

        # -------------------- If requested, read header at a specific position
        # read the rest of the bmp header, without its size
        header_data = ImageFile._safe_read(self.fp, file_info["header_size"] - 4)

        # -------------------------------------------------- IBM OS/2 Bitmap v1
        # ----- This format has different offsets because of width/height types
        if file_info["header_size"] == 12:
            file_info["width"] = i16(header_data[0:2])
            file_info["height"] = i16(header_data[2:4])
            file_info["planes"] = i16(header_data[4:6])
            file_info["bits"] = i16(header_data[6:8])
            file_info["compression"] = self.RAW
            file_info["palette_padding"] = 3

        # --------------------------------------------- Windows Bitmap v2 to v5
        # v3, OS/2 v2, v4, v5
        elif file_info["header_size"] in (40, 64, 108, 124):
            file_info["y_flip"] = i8(header_data[7]) == 0xFF
            file_info["direction"] = 1 if file_info["y_flip"] else -1
            file_info["width"] = i32(header_data[0:4])
            file_info["height"] = (
                i32(header_data[4:8])
                if not file_info["y_flip"]
                else 2 ** 32 - i32(header_data[4:8])
            )
            file_info["planes"] = i16(header_data[8:10])
            file_info["bits"] = i16(header_data[10:12])
            file_info["compression"] = i32(header_data[12:16])
            # byte size of pixel data
            file_info["data_size"] = i32(header_data[16:20])
            file_info["pixels_per_meter"] = (
                i32(header_data[20:24]),
                i32(header_data[24:28]),
            )
            file_info["colors"] = i32(header_data[28:32])
            file_info["palette_padding"] = 4
            self.info["dpi"] = tuple(
                int(x / 39.3701 + 0.5) for x in file_info["pixels_per_meter"]
            )
            if file_info["compression"] == self.BITFIELDS:
                if len(header_data) >= 52:
                    for idx, mask in enumerate(
                        ["r_mask", "g_mask", "b_mask", "a_mask"]
                    ):
                        file_info[mask] = i32(header_data[36 + idx * 4 : 40 + idx * 4])
                else:
                    # 40 byte headers only have the three components in the
                    # bitfields masks, ref:
                    # https://msdn.microsoft.com/en-us/library/windows/desktop/dd183376(v=vs.85).aspx
                    # See also
                    # https://github.com/python-pillow/Pillow/issues/1293
                    # There is a 4th component in the RGBQuad, in the alpha
                    # location, but it is listed as a reserved component,
                    # and it is not generally an alpha channel
                    file_info["a_mask"] = 0x0
                    for mask in ["r_mask", "g_mask", "b_mask"]:
                        file_info[mask] = i32(read(4))
                file_info["rgb_mask"] = (
                    file_info["r_mask"],
                    file_info["g_mask"],
                    file_info["b_mask"],
                )
                file_info["rgba_mask"] = (
                    file_info["r_mask"],
                    file_info["g_mask"],
                    file_info["b_mask"],
                    file_info["a_mask"],
                )
        else:
            raise OSError("Unsupported BMP header type (%d)" % file_info["header_size"])

        # ------------------ Special case : header is reported 40, which
        # ---------------------- is shorter than real size for bpp >= 16
        self._size = file_info["width"], file_info["height"]

        # ------- If color count was not found in the header, compute from bits
        file_info["colors"] = (
            file_info["colors"]
            if file_info.get("colors", 0)
            else (1 << file_info["bits"])
        )

        # ------------------------------- Check abnormal values for DOS attacks
        if file_info["width"] * file_info["height"] > 2 ** 31:
            raise OSError("Unsupported BMP Size: (%dx%d)" % self.size)

        # ---------------------- Check bit depth for unusual unsupported values
        self.mode, raw_mode = BIT2MODE.get(file_info["bits"], (None, None))
        if self.mode is None:
            raise OSError("Unsupported BMP pixel depth (%d)" % file_info["bits"])

        # ---------------- Process BMP with Bitfields compression (not palette)
        if file_info["compression"] == self.BITFIELDS:
            SUPPORTED = {
                32: [
                    (0xFF0000, 0xFF00, 0xFF, 0x0),
                    (0xFF0000, 0xFF00, 0xFF, 0xFF000000),
                    (0xFF, 0xFF00, 0xFF0000, 0xFF000000),
                    (0x0, 0x0, 0x0, 0x0),
                    (0xFF000000, 0xFF0000, 0xFF00, 0x0),
                ],
                24: [(0xFF0000, 0xFF00, 0xFF)],
                16: [(0xF800, 0x7E0, 0x1F), (0x7C00, 0x3E0, 0x1F)],
            }
            MASK_MODES = {
                (32, (0xFF0000, 0xFF00, 0xFF, 0x0)): "BGRX",
                (32, (0xFF000000, 0xFF0000, 0xFF00, 0x0)): "XBGR",
                (32, (0xFF, 0xFF00, 0xFF0000, 0xFF000000)): "RGBA",
                (32, (0xFF0000, 0xFF00, 0xFF, 0xFF000000)): "BGRA",
                (32, (0x0, 0x0, 0x0, 0x0)): "BGRA",
                (24, (0xFF0000, 0xFF00, 0xFF)): "BGR",
                (16, (0xF800, 0x7E0, 0x1F)): "BGR;16",
                (16, (0x7C00, 0x3E0, 0x1F)): "BGR;15",
            }
            if file_info["bits"] in SUPPORTED:
                if (
                    file_info["bits"] == 32
                    and file_info["rgba_mask"] in SUPPORTED[file_info["bits"]]
                ):
                    raw_mode = MASK_MODES[(file_info["bits"], file_info["rgba_mask"])]
                    self.mode = "RGBA" if "A" in raw_mode else self.mode
                elif (
                    file_info["bits"] in (24, 16)
                    and file_info["rgb_mask"] in SUPPORTED[file_info["bits"]]
                ):
                    raw_mode = MASK_MODES[(file_info["bits"], file_info["rgb_mask"])]
                else:
                    raise OSError("Unsupported BMP bitfields layout")
            else:
                raise OSError("Unsupported BMP bitfields layout")
        elif file_info["compression"] == self.RAW:
            if file_info["bits"] == 32 and header == 22:  # 32-bit .cur offset
                raw_mode, self.mode = "BGRA", "RGBA"
        else:
            raise OSError("Unsupported BMP compression (%d)" % file_info["compression"])

        # --------------- Once the header is processed, process the palette/LUT
        if self.mode == "P":  # Paletted for 1, 4 and 8 bit images

            # ---------------------------------------------------- 1-bit images
            if not (0 < file_info["colors"] <= 65536):
                raise OSError("Unsupported BMP Palette size (%d)" % file_info["colors"])
            else:
                padding = file_info["palette_padding"]
                palette = read(padding * file_info["colors"])
                greyscale = True
                indices = (
                    (0, 255)
                    if file_info["colors"] == 2
                    else list(range(file_info["colors"]))
                )

                # ----------------- Check if greyscale and ignore palette if so
                for ind, val in enumerate(indices):
                    rgb = palette[ind * padding : ind * padding + 3]
                    if rgb != o8(val) * 3:
                        greyscale = False

                # ------- If all colors are grey, white or black, ditch palette
                if greyscale:
                    self.mode = "1" if file_info["colors"] == 2 else "L"
                    raw_mode = self.mode
                else:
                    self.mode = "P"
                    self.palette = ImagePalette.raw(
                        "BGRX" if padding == 4 else "BGR", palette
                    )

        # ---------------------------- Finally set the tile data for the plugin
        self.info["compression"] = file_info["compression"]
        self.tile = [
            (
                "raw",
                (0, 0, file_info["width"], file_info["height"]),
                offset or self.fp.tell(),
                (
                    raw_mode,
                    ((file_info["width"] * file_info["bits"] + 31) >> 3) & (~3),
                    file_info["direction"],
                ),
            )
        ]

    def _open(self):
        """ Open file, check magic number and read header """
        # read 14 bytes: magic number, filesize, reserved, header final offset
        head_data = self.fp.read(14)
        # choke if the file does not have the required magic bytes
        if head_data[0:2] != b"BM":
            raise SyntaxError("Not a BMP file")
        # read the start position of the BMP image data (u32)
        offset = i32(head_data[10:14])
        # load bitmap information (offset=raster info)
        self._bitmap(offset=offset)


# =============================================================================
# Image plugin for the DIB format (BMP alias)
# =============================================================================
class DibImageFile(BmpImageFile):

    format = "DIB"
    format_description = "Windows Bitmap"

    def _open(self):
        self._bitmap()


#
# --------------------------------------------------------------------
# Write BMP file


SAVE = {
    "1": ("1", 1, 2),
    "L": ("L", 8, 256),
    "P": ("P", 8, 256),
    "RGB": ("BGR", 24, 0),
    "RGBA": ("BGRA", 32, 0),
}


def _dib_save(im, fp, filename):
    _save(im, fp, filename, False)


def _save(im, fp, filename, bitmap_header=True):
    try:
        rawmode, bits, colors = SAVE[im.mode]
    except KeyError:
        raise OSError("cannot write mode %s as BMP" % im.mode)

    info = im.encoderinfo

    dpi = info.get("dpi", (96, 96))

    # 1 meter == 39.3701 inches
    ppm = tuple(map(lambda x: int(x * 39.3701 + 0.5), dpi))

    stride = ((im.size[0] * bits + 7) // 8 + 3) & (~3)
    header = 40  # or 64 for OS/2 version 2
    image = stride * im.size[1]

    # bitmap header
    if bitmap_header:
        offset = 14 + header + colors * 4
        file_size = offset + image
        if file_size > 2 ** 32 - 1:
            raise ValueError("File size is too large for the BMP format")
        fp.write(
            b"BM"  # file type (magic)
            + o32(file_size)  # file size
            + o32(0)  # reserved
            + o32(offset)  # image data offset
        )

    # bitmap info header
    fp.write(
        o32(header)  # info header size
        + o32(im.size[0])  # width
        + o32(im.size[1])  # height
        + o16(1)  # planes
        + o16(bits)  # depth
        + o32(0)  # compression (0=uncompressed)
        + o32(image)  # size of bitmap
        + o32(ppm[0])  # resolution
        + o32(ppm[1])  # resolution
        + o32(colors)  # colors used
        + o32(colors)  # colors important
    )

    fp.write(b"\0" * (header - 40))  # padding (for OS/2 format)

    if im.mode == "1":
        for i in (0, 255):
            fp.write(o8(i) * 4)
    elif im.mode == "L":
        for i in range(256):
            fp.write(o8(i) * 4)
    elif im.mode == "P":
        fp.write(im.im.getpalette("RGB", "BGRX"))

    ImageFile._save(im, fp, [("raw", (0, 0) + im.size, 0, (rawmode, stride, -1))])


#
# --------------------------------------------------------------------
# Registry


Image.register_open(BmpImageFile.format, BmpImageFile, _accept)
Image.register_save(BmpImageFile.format, _save)

Image.register_extension(BmpImageFile.format, ".bmp")

Image.register_mime(BmpImageFile.format, "image/bmp")

Image.register_open(DibImageFile.format, DibImageFile, _dib_accept)
Image.register_save(DibImageFile.format, _dib_save)

Image.register_extension(DibImageFile.format, ".dib")

Image.register_mime(DibImageFile.format, "image/bmp")