153 lines
4.5 KiB
Python
153 lines
4.5 KiB
Python
#
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# The Python Imaging Library
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# $Id$
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#
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# FITS file handling
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#
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# Copyright (c) 1998-2003 by Fredrik Lundh
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#
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# See the README file for information on usage and redistribution.
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#
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from __future__ import annotations
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import gzip
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import math
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from . import Image, ImageFile
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def _accept(prefix: bytes) -> bool:
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return prefix[:6] == b"SIMPLE"
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class FitsImageFile(ImageFile.ImageFile):
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format = "FITS"
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format_description = "FITS"
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def _open(self) -> None:
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assert self.fp is not None
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headers: dict[bytes, bytes] = {}
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header_in_progress = False
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decoder_name = ""
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while True:
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header = self.fp.read(80)
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if not header:
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msg = "Truncated FITS file"
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raise OSError(msg)
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keyword = header[:8].strip()
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if keyword in (b"SIMPLE", b"XTENSION"):
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header_in_progress = True
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elif headers and not header_in_progress:
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# This is now a data unit
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break
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elif keyword == b"END":
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# Seek to the end of the header unit
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self.fp.seek(math.ceil(self.fp.tell() / 2880) * 2880)
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if not decoder_name:
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decoder_name, offset, args = self._parse_headers(headers)
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header_in_progress = False
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continue
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if decoder_name:
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# Keep going to read past the headers
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continue
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value = header[8:].split(b"/")[0].strip()
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if value.startswith(b"="):
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value = value[1:].strip()
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if not headers and (not _accept(keyword) or value != b"T"):
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msg = "Not a FITS file"
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raise SyntaxError(msg)
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headers[keyword] = value
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if not decoder_name:
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msg = "No image data"
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raise ValueError(msg)
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offset += self.fp.tell() - 80
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self.tile = [(decoder_name, (0, 0) + self.size, offset, args)]
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def _get_size(
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self, headers: dict[bytes, bytes], prefix: bytes
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) -> tuple[int, int] | None:
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naxis = int(headers[prefix + b"NAXIS"])
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if naxis == 0:
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return None
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if naxis == 1:
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return 1, int(headers[prefix + b"NAXIS1"])
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else:
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return int(headers[prefix + b"NAXIS1"]), int(headers[prefix + b"NAXIS2"])
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def _parse_headers(
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self, headers: dict[bytes, bytes]
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) -> tuple[str, int, tuple[str | int, ...]]:
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prefix = b""
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decoder_name = "raw"
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offset = 0
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if (
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headers.get(b"XTENSION") == b"'BINTABLE'"
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and headers.get(b"ZIMAGE") == b"T"
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and headers[b"ZCMPTYPE"] == b"'GZIP_1 '"
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):
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no_prefix_size = self._get_size(headers, prefix) or (0, 0)
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number_of_bits = int(headers[b"BITPIX"])
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offset = no_prefix_size[0] * no_prefix_size[1] * (number_of_bits // 8)
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prefix = b"Z"
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decoder_name = "fits_gzip"
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size = self._get_size(headers, prefix)
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if not size:
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return "", 0, ()
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self._size = size
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number_of_bits = int(headers[prefix + b"BITPIX"])
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if number_of_bits == 8:
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self._mode = "L"
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elif number_of_bits == 16:
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self._mode = "I;16"
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elif number_of_bits == 32:
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self._mode = "I"
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elif number_of_bits in (-32, -64):
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self._mode = "F"
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args: tuple[str | int, ...]
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if decoder_name == "raw":
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args = (self.mode, 0, -1)
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else:
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args = (number_of_bits,)
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return decoder_name, offset, args
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class FitsGzipDecoder(ImageFile.PyDecoder):
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_pulls_fd = True
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def decode(self, buffer: bytes) -> tuple[int, int]:
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assert self.fd is not None
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value = gzip.decompress(self.fd.read())
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rows = []
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offset = 0
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number_of_bits = min(self.args[0] // 8, 4)
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for y in range(self.state.ysize):
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row = bytearray()
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for x in range(self.state.xsize):
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row += value[offset + (4 - number_of_bits) : offset + 4]
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offset += 4
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rows.append(row)
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self.set_as_raw(bytes([pixel for row in rows[::-1] for pixel in row]))
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return -1, 0
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# --------------------------------------------------------------------
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# Registry
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Image.register_open(FitsImageFile.format, FitsImageFile, _accept)
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Image.register_decoder("fits_gzip", FitsGzipDecoder)
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Image.register_extensions(FitsImageFile.format, [".fit", ".fits"])
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