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- #
- # The Python Imaging Library.
- # $Id$
- #
- # SGI image file handling
- #
- # See "The SGI Image File Format (Draft version 0.97)", Paul Haeberli.
- # <ftp://ftp.sgi.com/graphics/SGIIMAGESPEC>
- #
- #
- # History:
- # 2017-22-07 mb Add RLE decompression
- # 2016-16-10 mb Add save method without compression
- # 1995-09-10 fl Created
- #
- # Copyright (c) 2016 by Mickael Bonfill.
- # Copyright (c) 2008 by Karsten Hiddemann.
- # Copyright (c) 1997 by Secret Labs AB.
- # Copyright (c) 1995 by Fredrik Lundh.
- #
- # See the README file for information on usage and redistribution.
- #
-
-
- import os
- import struct
-
- from . import Image, ImageFile
- from ._binary import i16be as i16
- from ._binary import o8
-
-
- def _accept(prefix):
- return len(prefix) >= 2 and i16(prefix) == 474
-
-
- MODES = {
- (1, 1, 1): "L",
- (1, 2, 1): "L",
- (2, 1, 1): "L;16B",
- (2, 2, 1): "L;16B",
- (1, 3, 3): "RGB",
- (2, 3, 3): "RGB;16B",
- (1, 3, 4): "RGBA",
- (2, 3, 4): "RGBA;16B",
- }
-
-
- ##
- # Image plugin for SGI images.
- class SgiImageFile(ImageFile.ImageFile):
- format = "SGI"
- format_description = "SGI Image File Format"
-
- def _open(self):
- # HEAD
- headlen = 512
- s = self.fp.read(headlen)
-
- if not _accept(s):
- msg = "Not an SGI image file"
- raise ValueError(msg)
-
- # compression : verbatim or RLE
- compression = s[2]
-
- # bpc : 1 or 2 bytes (8bits or 16bits)
- bpc = s[3]
-
- # dimension : 1, 2 or 3 (depending on xsize, ysize and zsize)
- dimension = i16(s, 4)
-
- # xsize : width
- xsize = i16(s, 6)
-
- # ysize : height
- ysize = i16(s, 8)
-
- # zsize : channels count
- zsize = i16(s, 10)
-
- # layout
- layout = bpc, dimension, zsize
-
- # determine mode from bits/zsize
- rawmode = ""
- try:
- rawmode = MODES[layout]
- except KeyError:
- pass
-
- if rawmode == "":
- msg = "Unsupported SGI image mode"
- raise ValueError(msg)
-
- self._size = xsize, ysize
- self.mode = rawmode.split(";")[0]
- if self.mode == "RGB":
- self.custom_mimetype = "image/rgb"
-
- # orientation -1 : scanlines begins at the bottom-left corner
- orientation = -1
-
- # decoder info
- if compression == 0:
- pagesize = xsize * ysize * bpc
- if bpc == 2:
- self.tile = [
- ("SGI16", (0, 0) + self.size, headlen, (self.mode, 0, orientation))
- ]
- else:
- self.tile = []
- offset = headlen
- for layer in self.mode:
- self.tile.append(
- ("raw", (0, 0) + self.size, offset, (layer, 0, orientation))
- )
- offset += pagesize
- elif compression == 1:
- self.tile = [
- ("sgi_rle", (0, 0) + self.size, headlen, (rawmode, orientation, bpc))
- ]
-
-
- def _save(im, fp, filename):
- if im.mode != "RGB" and im.mode != "RGBA" and im.mode != "L":
- msg = "Unsupported SGI image mode"
- raise ValueError(msg)
-
- # Get the keyword arguments
- info = im.encoderinfo
-
- # Byte-per-pixel precision, 1 = 8bits per pixel
- bpc = info.get("bpc", 1)
-
- if bpc not in (1, 2):
- msg = "Unsupported number of bytes per pixel"
- raise ValueError(msg)
-
- # Flip the image, since the origin of SGI file is the bottom-left corner
- orientation = -1
- # Define the file as SGI File Format
- magic_number = 474
- # Run-Length Encoding Compression - Unsupported at this time
- rle = 0
-
- # Number of dimensions (x,y,z)
- dim = 3
- # X Dimension = width / Y Dimension = height
- x, y = im.size
- if im.mode == "L" and y == 1:
- dim = 1
- elif im.mode == "L":
- dim = 2
- # Z Dimension: Number of channels
- z = len(im.mode)
-
- if dim == 1 or dim == 2:
- z = 1
-
- # assert we've got the right number of bands.
- if len(im.getbands()) != z:
- msg = f"incorrect number of bands in SGI write: {z} vs {len(im.getbands())}"
- raise ValueError(msg)
-
- # Minimum Byte value
- pinmin = 0
- # Maximum Byte value (255 = 8bits per pixel)
- pinmax = 255
- # Image name (79 characters max, truncated below in write)
- img_name = os.path.splitext(os.path.basename(filename))[0]
- img_name = img_name.encode("ascii", "ignore")
- # Standard representation of pixel in the file
- colormap = 0
- fp.write(struct.pack(">h", magic_number))
- fp.write(o8(rle))
- fp.write(o8(bpc))
- fp.write(struct.pack(">H", dim))
- fp.write(struct.pack(">H", x))
- fp.write(struct.pack(">H", y))
- fp.write(struct.pack(">H", z))
- fp.write(struct.pack(">l", pinmin))
- fp.write(struct.pack(">l", pinmax))
- fp.write(struct.pack("4s", b"")) # dummy
- fp.write(struct.pack("79s", img_name)) # truncates to 79 chars
- fp.write(struct.pack("s", b"")) # force null byte after img_name
- fp.write(struct.pack(">l", colormap))
- fp.write(struct.pack("404s", b"")) # dummy
-
- rawmode = "L"
- if bpc == 2:
- rawmode = "L;16B"
-
- for channel in im.split():
- fp.write(channel.tobytes("raw", rawmode, 0, orientation))
-
- if hasattr(fp, "flush"):
- fp.flush()
-
-
- class SGI16Decoder(ImageFile.PyDecoder):
- _pulls_fd = True
-
- def decode(self, buffer):
- rawmode, stride, orientation = self.args
- pagesize = self.state.xsize * self.state.ysize
- zsize = len(self.mode)
- self.fd.seek(512)
-
- for band in range(zsize):
- channel = Image.new("L", (self.state.xsize, self.state.ysize))
- channel.frombytes(
- self.fd.read(2 * pagesize), "raw", "L;16B", stride, orientation
- )
- self.im.putband(channel.im, band)
-
- return -1, 0
-
-
- #
- # registry
-
-
- Image.register_decoder("SGI16", SGI16Decoder)
- Image.register_open(SgiImageFile.format, SgiImageFile, _accept)
- Image.register_save(SgiImageFile.format, _save)
- Image.register_mime(SgiImageFile.format, "image/sgi")
-
- Image.register_extensions(SgiImageFile.format, [".bw", ".rgb", ".rgba", ".sgi"])
-
- # End of file
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