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MspImagePlugin.py 5.5KB

1 year ago
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  1. #
  2. # The Python Imaging Library.
  3. #
  4. # MSP file handling
  5. #
  6. # This is the format used by the Paint program in Windows 1 and 2.
  7. #
  8. # History:
  9. # 95-09-05 fl Created
  10. # 97-01-03 fl Read/write MSP images
  11. # 17-02-21 es Fixed RLE interpretation
  12. #
  13. # Copyright (c) Secret Labs AB 1997.
  14. # Copyright (c) Fredrik Lundh 1995-97.
  15. # Copyright (c) Eric Soroos 2017.
  16. #
  17. # See the README file for information on usage and redistribution.
  18. #
  19. # More info on this format: https://archive.org/details/gg243631
  20. # Page 313:
  21. # Figure 205. Windows Paint Version 1: "DanM" Format
  22. # Figure 206. Windows Paint Version 2: "LinS" Format. Used in Windows V2.03
  23. #
  24. # See also: https://www.fileformat.info/format/mspaint/egff.htm
  25. import io
  26. import struct
  27. from . import Image, ImageFile
  28. from ._binary import i16le as i16
  29. from ._binary import o16le as o16
  30. #
  31. # read MSP files
  32. def _accept(prefix):
  33. return prefix[:4] in [b"DanM", b"LinS"]
  34. ##
  35. # Image plugin for Windows MSP images. This plugin supports both
  36. # uncompressed (Windows 1.0).
  37. class MspImageFile(ImageFile.ImageFile):
  38. format = "MSP"
  39. format_description = "Windows Paint"
  40. def _open(self):
  41. # Header
  42. s = self.fp.read(32)
  43. if not _accept(s):
  44. msg = "not an MSP file"
  45. raise SyntaxError(msg)
  46. # Header checksum
  47. checksum = 0
  48. for i in range(0, 32, 2):
  49. checksum = checksum ^ i16(s, i)
  50. if checksum != 0:
  51. msg = "bad MSP checksum"
  52. raise SyntaxError(msg)
  53. self.mode = "1"
  54. self._size = i16(s, 4), i16(s, 6)
  55. if s[:4] == b"DanM":
  56. self.tile = [("raw", (0, 0) + self.size, 32, ("1", 0, 1))]
  57. else:
  58. self.tile = [("MSP", (0, 0) + self.size, 32, None)]
  59. class MspDecoder(ImageFile.PyDecoder):
  60. # The algo for the MSP decoder is from
  61. # https://www.fileformat.info/format/mspaint/egff.htm
  62. # cc-by-attribution -- That page references is taken from the
  63. # Encyclopedia of Graphics File Formats and is licensed by
  64. # O'Reilly under the Creative Common/Attribution license
  65. #
  66. # For RLE encoded files, the 32byte header is followed by a scan
  67. # line map, encoded as one 16bit word of encoded byte length per
  68. # line.
  69. #
  70. # NOTE: the encoded length of the line can be 0. This was not
  71. # handled in the previous version of this encoder, and there's no
  72. # mention of how to handle it in the documentation. From the few
  73. # examples I've seen, I've assumed that it is a fill of the
  74. # background color, in this case, white.
  75. #
  76. #
  77. # Pseudocode of the decoder:
  78. # Read a BYTE value as the RunType
  79. # If the RunType value is zero
  80. # Read next byte as the RunCount
  81. # Read the next byte as the RunValue
  82. # Write the RunValue byte RunCount times
  83. # If the RunType value is non-zero
  84. # Use this value as the RunCount
  85. # Read and write the next RunCount bytes literally
  86. #
  87. # e.g.:
  88. # 0x00 03 ff 05 00 01 02 03 04
  89. # would yield the bytes:
  90. # 0xff ff ff 00 01 02 03 04
  91. #
  92. # which are then interpreted as a bit packed mode '1' image
  93. _pulls_fd = True
  94. def decode(self, buffer):
  95. img = io.BytesIO()
  96. blank_line = bytearray((0xFF,) * ((self.state.xsize + 7) // 8))
  97. try:
  98. self.fd.seek(32)
  99. rowmap = struct.unpack_from(
  100. f"<{self.state.ysize}H", self.fd.read(self.state.ysize * 2)
  101. )
  102. except struct.error as e:
  103. msg = "Truncated MSP file in row map"
  104. raise OSError(msg) from e
  105. for x, rowlen in enumerate(rowmap):
  106. try:
  107. if rowlen == 0:
  108. img.write(blank_line)
  109. continue
  110. row = self.fd.read(rowlen)
  111. if len(row) != rowlen:
  112. msg = f"Truncated MSP file, expected {rowlen} bytes on row {x}"
  113. raise OSError(msg)
  114. idx = 0
  115. while idx < rowlen:
  116. runtype = row[idx]
  117. idx += 1
  118. if runtype == 0:
  119. (runcount, runval) = struct.unpack_from("Bc", row, idx)
  120. img.write(runval * runcount)
  121. idx += 2
  122. else:
  123. runcount = runtype
  124. img.write(row[idx : idx + runcount])
  125. idx += runcount
  126. except struct.error as e:
  127. msg = f"Corrupted MSP file in row {x}"
  128. raise OSError(msg) from e
  129. self.set_as_raw(img.getvalue(), ("1", 0, 1))
  130. return -1, 0
  131. Image.register_decoder("MSP", MspDecoder)
  132. #
  133. # write MSP files (uncompressed only)
  134. def _save(im, fp, filename):
  135. if im.mode != "1":
  136. msg = f"cannot write mode {im.mode} as MSP"
  137. raise OSError(msg)
  138. # create MSP header
  139. header = [0] * 16
  140. header[0], header[1] = i16(b"Da"), i16(b"nM") # version 1
  141. header[2], header[3] = im.size
  142. header[4], header[5] = 1, 1
  143. header[6], header[7] = 1, 1
  144. header[8], header[9] = im.size
  145. checksum = 0
  146. for h in header:
  147. checksum = checksum ^ h
  148. header[12] = checksum # FIXME: is this the right field?
  149. # header
  150. for h in header:
  151. fp.write(o16(h))
  152. # image body
  153. ImageFile._save(im, fp, [("raw", (0, 0) + im.size, 32, ("1", 0, 1))])
  154. #
  155. # registry
  156. Image.register_open(MspImageFile.format, MspImageFile, _accept)
  157. Image.register_save(MspImageFile.format, _save)
  158. Image.register_extension(MspImageFile.format, ".msp")