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8.2 KiB

import struct
from sys import maxsize as INF
## PNG Predictor
##
def apply_png_predictor(pred, colors, columns, bitspercomponent, data):
if bitspercomponent != 8:
# unsupported
raise ValueError(bitspercomponent)
nbytes = colors*columns*bitspercomponent//8
i = 0
buf = b''
line0 = b'\x00' * columns
while i < len(data):
pred = data[i]
i += 1
line1 = data[i:i+nbytes]
i += nbytes
if pred == 0:
# PNG none
buf += line1
elif pred == 1:
# PNG sub (UNTESTED)
c = 0
bufline = []
for b in line1:
c = (c+b) & 255
bufline.append(c)
buf += bytes(bufline)
elif pred == 2:
# PNG up
bufline = []
for (a,b) in zip(line0,line1):
c = (a+b) & 255
bufline.append(c)
buf += bytes(bufline)
elif pred == 3:
# PNG average (UNTESTED)
c = 0
bufline = []
for (a,b) in zip(line0,line1):
c = ((c+a+b)//2) & 255
bufline.append(c)
buf += bytes(bufline)
else:
# unsupported
raise ValueError(pred)
line0 = line1
return buf
## Matrix operations
##
MATRIX_IDENTITY = (1, 0, 0, 1, 0, 0)
def mult_matrix(matrix1, matrix2):
"""Returns the multiplication of two matrices."""
(a1,b1,c1,d1,e1,f1) = matrix1
(a0,b0,c0,d0,e0,f0) = matrix2
return (a0*a1+c0*b1, b0*a1+d0*b1,
a0*c1+c0*d1, b0*c1+d0*d1,
a0*e1+c0*f1+e0, b0*e1+d0*f1+f0)
def translate_matrix(matrix, point):
"""Translates a matrix by (x,y)."""
(a,b,c,d,e,f) = matrix
(x,y) = point
return (a,b,c,d,x*a+y*c+e,x*b+y*d+f)
def apply_matrix_pt(matrix, point):
"""Applies a matrix to a point."""
(a,b,c,d,e,f) = matrix
(x,y) = point
return (a*x+c*y+e, b*x+d*y+f)
def apply_matrix_norm(matrix, norm):
"""Equivalent to apply_matrix_pt(M, (p,q)) - apply_matrix_pt(M, (0,0))"""
(a,b,c,d,e,f) = matrix
(p,q) = norm
return (a*p+c*q, b*p+d*q)
## Utility functions
##
# uniq
def uniq(objs):
"""Eliminates duplicated elements."""
done = set()
for obj in objs:
if obj in done: continue
done.add(obj)
yield obj
# fsplit
def fsplit(pred, objs):
"""Split a list into two classes according to the predicate."""
t = []
f = []
for obj in objs:
if pred(obj):
t.append(obj)
else:
f.append(obj)
return (t,f)
# drange
def drange(v0, v1, d):
"""Returns a discrete range."""
assert v0 < v1
return range(int(v0)//d, int(v1+d)//d)
# get_bound
def get_bound(pts):
"""Compute a minimal rectangle that covers all the points."""
(x0, y0, x1, y1) = (INF, INF, -INF, -INF)
for (x,y) in pts:
x0 = min(x0, x)
y0 = min(y0, y)
x1 = max(x1, x)
y1 = max(y1, y)
return (x0,y0,x1,y1)
# pick
def pick(seq, func, maxobj=None):
"""Picks the object obj where func(obj) has the highest value."""
maxscore = None
for obj in seq:
score = func(obj)
if maxscore is None or maxscore < score:
(maxscore,maxobj) = (score,obj)
return maxobj
# choplist
def choplist(n, seq):
"""Groups every n elements of the list."""
r = []
for x in seq:
r.append(x)
if len(r) == n:
yield tuple(r)
r = []
def trailiter(iterable, skipfirst=False):
"""Yields (prev_element, element), starting with (None, first_element).
If skipfirst is True, there will be no (None, item1) element and we'll start
directly with (item1, item2).
"""
it = iter(iterable)
if skipfirst:
prev = next(it)
else:
prev = None
for item in it:
yield prev, item
prev = item
# nunpack
def nunpack(b, default=0):
"""Unpacks 1 to 4 byte integers (big endian)."""
if isinstance(b, str):
b = b.encode('latin-1')
l = len(b)
if not l:
return default
elif l == 1:
return b[0]
elif l == 2:
return struct.unpack(b'>H', b)[0]
elif l == 3:
return struct.unpack(b'>L', b'\x00'+b)[0]
elif l == 4:
return struct.unpack(b'>L', b)[0]
else:
raise TypeError('invalid length: %d' % l)
# decode_text
PDFDocEncoding = ''.join( chr(x) for x in (
0x0000, 0x0001, 0x0002, 0x0003, 0x0004, 0x0005, 0x0006, 0x0007,
0x0008, 0x0009, 0x000a, 0x000b, 0x000c, 0x000d, 0x000e, 0x000f,
0x0010, 0x0011, 0x0012, 0x0013, 0x0014, 0x0015, 0x0017, 0x0017,
0x02d8, 0x02c7, 0x02c6, 0x02d9, 0x02dd, 0x02db, 0x02da, 0x02dc,
0x0020, 0x0021, 0x0022, 0x0023, 0x0024, 0x0025, 0x0026, 0x0027,
0x0028, 0x0029, 0x002a, 0x002b, 0x002c, 0x002d, 0x002e, 0x002f,
0x0030, 0x0031, 0x0032, 0x0033, 0x0034, 0x0035, 0x0036, 0x0037,
0x0038, 0x0039, 0x003a, 0x003b, 0x003c, 0x003d, 0x003e, 0x003f,
0x0040, 0x0041, 0x0042, 0x0043, 0x0044, 0x0045, 0x0046, 0x0047,
0x0048, 0x0049, 0x004a, 0x004b, 0x004c, 0x004d, 0x004e, 0x004f,
0x0050, 0x0051, 0x0052, 0x0053, 0x0054, 0x0055, 0x0056, 0x0057,
0x0058, 0x0059, 0x005a, 0x005b, 0x005c, 0x005d, 0x005e, 0x005f,
0x0060, 0x0061, 0x0062, 0x0063, 0x0064, 0x0065, 0x0066, 0x0067,
0x0068, 0x0069, 0x006a, 0x006b, 0x006c, 0x006d, 0x006e, 0x006f,
0x0070, 0x0071, 0x0072, 0x0073, 0x0074, 0x0075, 0x0076, 0x0077,
0x0078, 0x0079, 0x007a, 0x007b, 0x007c, 0x007d, 0x007e, 0x0000,
0x2022, 0x2020, 0x2021, 0x2026, 0x2014, 0x2013, 0x0192, 0x2044,
0x2039, 0x203a, 0x2212, 0x2030, 0x201e, 0x201c, 0x201d, 0x2018,
0x2019, 0x201a, 0x2122, 0xfb01, 0xfb02, 0x0141, 0x0152, 0x0160,
0x0178, 0x017d, 0x0131, 0x0142, 0x0153, 0x0161, 0x017e, 0x0000,
0x20ac, 0x00a1, 0x00a2, 0x00a3, 0x00a4, 0x00a5, 0x00a6, 0x00a7,
0x00a8, 0x00a9, 0x00aa, 0x00ab, 0x00ac, 0x0000, 0x00ae, 0x00af,
0x00b0, 0x00b1, 0x00b2, 0x00b3, 0x00b4, 0x00b5, 0x00b6, 0x00b7,
0x00b8, 0x00b9, 0x00ba, 0x00bb, 0x00bc, 0x00bd, 0x00be, 0x00bf,
0x00c0, 0x00c1, 0x00c2, 0x00c3, 0x00c4, 0x00c5, 0x00c6, 0x00c7,
0x00c8, 0x00c9, 0x00ca, 0x00cb, 0x00cc, 0x00cd, 0x00ce, 0x00cf,
0x00d0, 0x00d1, 0x00d2, 0x00d3, 0x00d4, 0x00d5, 0x00d6, 0x00d7,
0x00d8, 0x00d9, 0x00da, 0x00db, 0x00dc, 0x00dd, 0x00de, 0x00df,
0x00e0, 0x00e1, 0x00e2, 0x00e3, 0x00e4, 0x00e5, 0x00e6, 0x00e7,
0x00e8, 0x00e9, 0x00ea, 0x00eb, 0x00ec, 0x00ed, 0x00ee, 0x00ef,
0x00f0, 0x00f1, 0x00f2, 0x00f3, 0x00f4, 0x00f5, 0x00f6, 0x00f7,
0x00f8, 0x00f9, 0x00fa, 0x00fb, 0x00fc, 0x00fd, 0x00fe, 0x00ff,
))
def decode_text(s):
"""Decodes a PDFDocEncoding string to Unicode."""
if s.startswith('\xfe\xff'):
return str(s[2:], 'utf-16be', 'ignore')
else:
return ''.join( PDFDocEncoding[ord(c)] for c in s )
def htmlescape(s, encoding='ascii'):
"""Escapes a string for SGML/XML/HTML"""
s = s.replace('&','&amp;').replace('>','&gt;').replace('<','&lt;').replace('"','&quot;')
# Additionally to basic replaces, we also make sure that all characters are convertible to our
# target encoding. If they're not, they're replaced by XML entities.
encoded = s.encode(encoding, errors='xmlcharrefreplace')
return encoded.decode(encoding)
def bbox2str(bbox):
(x0,y0,x1,y1) = bbox
return '%.3f,%.3f,%.3f,%.3f' % (x0, y0, x1, y1)
def matrix2str(matrix):
(a,b,c,d,e,f) = matrix
return '[%.2f,%.2f,%.2f,%.2f, (%.2f,%.2f)]' % (a,b,c,d,e,f)
def set_debug_logging():
import logging, sys
logging.basicConfig(level=logging.DEBUG, stream=sys.stderr)
class ObjIdRange:
"A utility class to represent a range of object IDs."
def __init__(self, start, nobjs):
self.start = start
self.nobjs = nobjs
def __repr__(self):
return '<ObjIdRange: %d-%d>' % (self.get_start_id(), self.get_end_id())
def get_start_id(self):
return self.start
def get_end_id(self):
return self.start + self.nobjs - 1
def get_nobjs(self):
return self.nobjs
# create_bmp
def create_bmp(data, bits, width, height):
info = struct.pack('<IiiHHIIIIII', 40, width, height, 1, bits, 0, len(data), 0, 0, 0, 0)
assert len(info) == 40, len(info)
header = struct.pack('<ccIHHI', 'B', 'M', 14+40+len(data), 0, 0, 14+40)
assert len(header) == 14, len(header)
# XXX re-rasterize every line
return header+info+data