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