def __init__(self, filename, beg, end, reverse=False):
'''Multifile initialization. Open the file.
Here I use the read routine which returns byte objects
(everything is an object in python). I use struct.unpack
to convert the byte object to other data type (int object
etc)
NOTE: At each record n, the file cursor points to record n+1
'''
self.FID = open(filename, "rb")
# self.FID.seek(0,os.SEEK_SET)
self.filename = filename
#br: bytes read
br = self.FID.read(1024)
self.beg = beg
self.end = end
self.reverse = reverse
ms_keys = [
'beam_center_x', 'beam_center_y', 'count_time',
'detector_distance', 'frame_time', 'incident_wavelength',
'x_pixel_size', 'y_pixel_size', 'bytes', 'nrows', 'ncols',
'rows_begin', 'rows_end', 'cols_begin', 'cols_end'
]
magic = struct.unpack('@16s', br[:16])
md_temp = struct.unpack('@8d7I916x', br[16:])
self.md = dict(zip(ms_keys, md_temp))
self.imgread = 0
self.recno = 0
if reverse:
nrows = self.md['nrows']
ncols = self.md['ncols']
self.md['nrows'] = ncols
self.md['ncols'] = nrows
rbeg = self.md['rows_begin']
rend = self.md['rows_end']
cbeg = self.md['cols_begin']
cend = self.md['cols_end']
self.md['rows_begin'] = cbeg
self.md['rows_end'] = cend
self.md['cols_begin'] = rbeg
self.md['cols_end'] = rend
# some initialization stuff
self.byts = self.md['bytes']
if (self.byts == 2):
self.valtype = np.uint16
elif (self.byts == 4):
self.valtype = np.uint32
elif (self.byts == 8):
self.valtype = np.float64
#now convert pieces of these bytes to our data
self.dlen = np.fromfile(self.FID, dtype=np.int32, count=1)[0]
def seekimg(self, n=None):
'''Position file to read the nth image.
For now only reads first image ignores n
'''
# the logic involving finding the cursor position
if (n is None):
n = self.recno
if (n < self.beg or n > self.end):
raise IndexError('Error, record out of range')
#print (n, self.recno, self.FID.tell() )
if ((n == self.recno) and (self.imgread == 0)):
pass # do nothing
else:
if (n <= self.recno): #ensure cursor less than search pos
self.FID.seek(1024, os.SEEK_SET)
self.dlen = np.fromfile(self.FID, dtype=np.int32, count=1)[0]
self.recno = 0
self.imgread = 0
if n == 0:
return
#have to iterate on seeking since dlen varies
#remember for rec recno, cursor is always at recno+1
if (self.imgread == 0): #move to next header if need to
self.FID.seek(self.dlen * (4 + self.byts), os.SEEK_CUR)
for i in range(self.recno + 1, n):
#the less seeks performed the faster
#print (i)
self.dlen = np.fromfile(self.FID, dtype=np.int32, count=1)[0]
#print 's',self.dlen
self.FID.seek(self.dlen * (4 + self.byts), os.SEEK_CUR)
# we are now at recno in file, read the header and data
#self._clearImage()
self._readHeader()
self.imgread = 0
self.recno = n
def _readImageRaw(self):
p = np.fromfile(self.FID, dtype=np.int32, count=self.dlen)
v = np.fromfile(self.FID, dtype=self.valtype, count=self.dlen)
self.imgread = 1
return (p, v)
def _readHeader(self):
self.dlen = np.fromfile(self.FID, dtype=np.int32, count=1)[0]