Pure Python MSP Decoder

PIL/MspImagePlugin.py

@@ -1,6 +1,5 @@
 #
 # The Python Imaging Library.
-# $Id$
 #
 # MSP file handling
 #
@@ -9,9 +8,11 @@
 # History:
 #       95-09-05 fl     Created
 #       97-01-03 fl     Read/write MSP images
+#       17-02-21 es     Fixed RLE interpretation
 #
 # Copyright (c) Secret Labs AB 1997.
 # Copyright (c) Fredrik Lundh 1995-97.
+# Copyright (c) Eric Soroos 2017.
 #
 # See the README file for information on usage and redistribution.
 #
@@ -20,9 +21,11 @@
 # Figure 205. Windows Paint Version 1: "DanM" Format
 # Figure 206. Windows Paint Version 2: "LinS" Format. Used in Windows V2.03
 #
+# See also: http://www.fileformat.info/format/mspaint/egff.htm
 
 from . import Image, ImageFile
 from ._binary import i16le as i16, o16le as o16
+import struct, io
 
 __version__ = "0.1"
 
@@ -64,7 +67,91 @@ class MspImageFile(ImageFile.ImageFile):
         if s[:4] == b"DanM":
             self.tile = [("raw", (0, 0)+self.size, 32, ("1", 0, 1))]
         else:
-            self.tile = [("msp", (0, 0)+self.size, 32+2*self.size[1], None)]
+            self.tile = [("MSP", (0, 0)+self.size, 32, None)]
+
+
+class MspDecoder(ImageFile.PyDecoder):
+    # The algo for the MSP decoder is from
+    # http://www.fileformat.info/format/mspaint/egff.htm
+    # cc-by-attribution -- That page references is taken from the
+    # Encyclopedia of Graphics File Formats and is licensed by
+    # O'Reilly under the Creative Common/Attribution license
+    #
+    # For RLE encoded files, the 32byte header is followed by a scan
+    # line map, encoded as one 16bit word of encoded byte length per
+    # line.
+    #
+    # NOTE: the encoded length of the line can be 0. This was not
+    # handled in the previous version of this encoder, and there's no
+    # mention of how to handle it in the documentation. From the few
+    # examples I've seen, I've assumed that it is a fill of the
+    # background color, in this case, white.
+    #
+    #
+    # Pseudocode of the decoder:
+    # Read a BYTE value as the RunType
+	#  If the RunType value is zero
+	# 	Read next byte as the RunCount
+	# 	Read the next byte as the RunValue
+	# 	Write the RunValue byte RunCount times
+	#  If the RunType value is non-zero
+	# 	Use this value as the RunCount
+	# 	Read and write the next RunCount bytes literally
+    # 
+    #  e.g.:
+    #  0x00 03 ff 05 00 01 02 03 04
+    #  would yield the bytes:
+    #  0xff ff ff 00 01 02 03 04
+    #
+    # which are then interpreted as a bit packed mode '1' image
+
+    
+    _pulls_fd = True
+
+    def decode(self, buffer):
+        
+        img = io.BytesIO()
+        blank_line = bytearray((0xff,)*((self.state.xsize+7)//8))
+        try:
+            last_pos = 0
+            self.fd.seek(32)
+            rowmap = struct.unpack_from("<%dH" % (self.state.ysize),
+                                        self.fd.read(self.state.ysize*2))
+        except struct.error:
+            raise IOError("Truncated MSP file in row map")
+
+        for x, rowlen in enumerate(rowmap):
+            try:
+                if rowlen == 0:
+                    img.write(blank_line)
+                    continue
+                row = self.fd.read(rowlen)
+                if len(row) != rowlen:
+                    raise IOError("Truncated MSP file, expected %d bytes on row %s",
+                                  (rowlen, x))
+                idx = 0
+                while idx < rowlen:
+                    runtype = row[idx]
+                    idx += 1
+                    if runtype == 0:
+                        (runcount, runval) = struct.unpack("Bc", row[idx:idx+2])
+                        img.write(runval * runcount)
+                        idx += 2
+                    else:
+                        runcount = runtype
+                        img.write(row[idx:idx+runcount])
+                        idx += runcount
+                        
+            except struct.error:
+                raise IOError("Corrupted MSP file in row %d" %x)
+            
+        self.set_as_raw(img.getvalue(), ("1", 0, 1))
+                
+        return 0,0
+
+
+Image.register_decoder('MSP', MspDecoder)
+   
 
 #
 # write MSP files (uncompressed only)

_imaging.c

@@ -3290,7 +3290,6 @@ extern PyObject* PyImaging_JpegDecoderNew(PyObject* self, PyObject* args);
 extern PyObject* PyImaging_Jpeg2KDecoderNew(PyObject* self, PyObject* args);
 extern PyObject* PyImaging_TiffLzwDecoderNew(PyObject* self, PyObject* args);
 extern PyObject* PyImaging_LibTiffDecoderNew(PyObject* self, PyObject* args);
-extern PyObject* PyImaging_MspDecoderNew(PyObject* self, PyObject* args);
 extern PyObject* PyImaging_PackbitsDecoderNew(PyObject* self, PyObject* args);
 extern PyObject* PyImaging_PcdDecoderNew(PyObject* self, PyObject* args);
 extern PyObject* PyImaging_PcxDecoderNew(PyObject* self, PyObject* args);
@@ -3368,7 +3367,6 @@ static PyMethodDef functions[] = {
     {"libtiff_decoder", (PyCFunction)PyImaging_LibTiffDecoderNew, 1},
     {"libtiff_encoder", (PyCFunction)PyImaging_LibTiffEncoderNew, 1},
 #endif
-    {"msp_decoder", (PyCFunction)PyImaging_MspDecoderNew, 1},
     {"packbits_decoder", (PyCFunction)PyImaging_PackbitsDecoderNew, 1},
     {"pcd_decoder", (PyCFunction)PyImaging_PcdDecoderNew, 1},
     {"pcx_decoder", (PyCFunction)PyImaging_PcxDecoderNew, 1},

decode.c

@@ -557,27 +557,6 @@ PyImaging_LibTiffDecoderNew(PyObject* self, PyObject* args)
 
 #endif
 
-/* -------------------------------------------------------------------- */
-/* MSP                                                                  */
-/* -------------------------------------------------------------------- */
-
-PyObject*
-PyImaging_MspDecoderNew(PyObject* self, PyObject* args)
-{
-    ImagingDecoderObject* decoder;
-
-    decoder = PyImaging_DecoderNew(0);
-    if (decoder == NULL)
-        return NULL;
-
-    if (get_unpacker(decoder, "1", "1") < 0)
-        return NULL;
-
-    decoder->decode = ImagingMspDecode;
-
-    return (PyObject*) decoder;
-}
-
 
 /* -------------------------------------------------------------------- */
 /* PackBits                                                             */

libImaging/MspDecode.c

@@ -1,91 +0,0 @@
-/*
- * The Python Imaging Library.
- * $Id$
- *
- * decoder for MSP version 2 data.
- *
- * history:
- *	97-01-03 fl	Created
- *
- * Copyright (c) Fredrik Lundh 1997.
- * Copyright (c) Secret Labs AB 1997.
- *
- * See the README file for information on usage and redistribution.
- */
-
-
-#include "Imaging.h"
-
-
-int
-ImagingMspDecode(Imaging im, ImagingCodecState state, UINT8* buf, int bytes)
-{
-    int n;
-    UINT8* ptr;
-
-    ptr = buf;
-
-    for (;;) {
-
-	if (bytes < 1)
-	    return ptr - buf;
-
-	if (ptr[0] == 0) {
-
-	    /* Run (3 bytes block) */
-	    if (bytes < 3)
-		break;
-
-	    n = ptr[1];
-
-	    if (state->x + n > state->bytes) {
-		state->errcode = IMAGING_CODEC_OVERRUN;
-		return -1;
-	    }
-
-	    memset(state->buffer + state->x, ptr[2], n);
-
-	    ptr += 3;
-	    bytes -= 3;
-
-	} else {
-
-	    /* Literal (1+n bytes block) */
-	    n = ptr[0];
-
-	    if (bytes < 1 + n)
-		break;
-
-	    if (state->x + n > state->bytes) {
-		state->errcode = IMAGING_CODEC_OVERRUN;
-		return -1;
-	    }
-
-	    memcpy(state->buffer + state->x, ptr + 1, n);
-
-	    ptr += 1 + n;
-	    bytes -= 1 + n;
-
-	}
-
-	state->x += n;
-
-	if (state->x >= state->bytes) {
-
-	    /* Got a full line, unpack it */
-	    state->shuffle((UINT8*) im->image[state->y + state->yoff] +
-			   state->xoff * im->pixelsize, state->buffer,
-			   state->xsize);
-
-	    state->x = 0;
-
-	    if (++state->y >= state->ysize) {
-		/* End of file (errcode = 0) */
-		return -1;
-	    }
-	}
-
-    }
-
-    return ptr - buf;
-}

setup.py

@@ -32,7 +32,7 @@ _LIB_IMAGING = (
     "Draw", "Effects", "EpsEncode", "File", "Fill", "Filter", "FliDecode",
     "Geometry", "GetBBox", "GifDecode", "GifEncode", "HexDecode", "Histo",
     "JpegDecode", "JpegEncode", "LzwDecode", "Matrix", "ModeFilter",
-    "MspDecode", "Negative", "Offset", "Pack", "PackDecode", "Palette", "Paste",
+    "Negative", "Offset", "Pack", "PackDecode", "Palette", "Paste",
     "Quant", "QuantOctree", "QuantHash", "QuantHeap", "PcdDecode", "PcxDecode",
     "PcxEncode", "Point", "RankFilter", "RawDecode", "RawEncode", "Storage",
     "SunRleDecode", "TgaRleDecode", "Unpack", "UnpackYCC", "UnsharpMask",