/
BmpImagePlugin.py
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/
BmpImagePlugin.py
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#
# 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 i16le as i16
from ._binary import i32le as i32
from ._binary import o8
from ._binary import o16le as o16
from ._binary import 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) 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)
file_info["height"] = i16(header_data, 2)
file_info["planes"] = i16(header_data, 4)
file_info["bits"] = i16(header_data, 6)
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"] = header_data[7] == 0xFF
file_info["direction"] = 1 if file_info["y_flip"] else -1
file_info["width"] = i32(header_data, 0)
file_info["height"] = (
i32(header_data, 4)
if not file_info["y_flip"]
else 2 ** 32 - i32(header_data, 4)
)
file_info["planes"] = i16(header_data, 8)
file_info["bits"] = i16(header_data, 10)
file_info["compression"] = i32(header_data, 12)
# byte size of pixel data
file_info["data_size"] = i32(header_data, 16)
file_info["pixels_per_meter"] = (
i32(header_data, 20),
i32(header_data, 24),
)
file_info["colors"] = i32(header_data, 28)
file_info["palette_padding"] = 4
self.info["dpi"] = tuple(x / 39.3701 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)
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(f"Unsupported BMP header type ({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"])
)
if offset == 14 + file_info["header_size"] and file_info["bits"] <= 8:
offset += 4 * file_info["colors"]
# ---------------------- 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(f"Unsupported BMP pixel depth ({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(f"Unsupported BMP compression ({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(f"Unsupported BMP Palette size ({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 not _accept(head_data):
raise SyntaxError("Not a BMP file")
# read the start position of the BMP image data (u32)
offset = i32(head_data, 10)
# 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 as e:
raise OSError(f"cannot write mode {im.mode} as BMP") from e
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")