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from bitarray import bitarray, bits2bytes
class PBM: # Portable Bitmap
def __init__(self, w = 0, h = 0):
self.size = w, h
self.update()
self.data = bitarray(self.bits, endian='big')
def update(self):
w, h = self.size
self.bytes_per_row = bits2bytes(w)
self.bits_per_row = 8 * self.bytes_per_row
self.bytes = self.bytes_per_row * h
self.bits = 8 * self.bytes
def info(self):
print('size: %d x %d' % self.size)
print('bytes per row: %d' % self.bytes_per_row)
print('bits per row: %d' % self.bits_per_row)
print('bitarray: ' + repr(self.data.buffer_info()))
def clear(self):
self.data.setall(0)
def save(self, filename):
with open(filename, 'wb') as fo:
fo.write(b'P4\n')
fo.write(b'# This is a partable bitmap (pbm) file.\n')
fo.write(('%d %d\n' % self.size).encode())
self.data.tofile(fo)
def load(self, filename):
with open(filename, 'rb') as fi:
assert fi.readline().strip() == b'P4'
while True:
line = fi.readline()
if not line.startswith(b'#'):
self.size = tuple(map(int, line.split()))
break
self.update()
self.data = bitarray(endian='big')
self.data.fromfile(fi)
fi.close()
assert self.data.nbytes == self.bytes
def address(self, pt):
x, y = pt
return x + self.bits_per_row * y
def __getitem__(self, pt):
return self.data[self.address(pt)]
def __setitem__(self, pt, val):
self.data[self.address(pt)] = val
if __name__ == '__main__':
# draw picture with straight line from (10, 10) to (390, 390)
a = PBM(500, 400)
a.info()
a.clear()
for x in range(10, 391):
a[x, x] = True
a.save('pic1.ppm')
# copy the picture
b = PBM()
b.load('pic1.ppm')
b.save('pic2.ppm')
# draw a straight line from (490, 10) to (110, 390) on top
for i in range(381):
b[490 - i, 10 + i] = 1
b.save('pic3.ppm')
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