Source code for fabio.readbytestream

#!/usr/bin/env python
#coding: utf8

"""
Reads a bytestream

Authors: Jon Wright    Henning O. Sorensen & Erik Knudsen
         ESRF          Risoe National Laboratory
"""

import numpy, logging
logger = logging.getLogger("readbytestream")
DATATYPES = {
    # type  sign bytes
    ("int", 'n', 1) : numpy.uint8,
    ("int", 'n', 2) : numpy.uint16,
    ("int", 'n', 4) : numpy.uint32,
    ("int", 'y', 1) : numpy.int8,
    ("int", 'y', 2) : numpy.int16,
    ("int", 'y', 4) : numpy.int32,
    ('float', 'y', 4) : numpy.float32, # does this occur in bruker?
    ('double', 'y', 4): numpy.float64
    }


[docs]def readbytestream(fil, offset, x, y, nbytespp, datatype='int', signed='n', swap='n', typeout=numpy.uint16): """ Reads in a bytestream from a file (which may be a string indicating a filename, or an already opened file (should be "rb")) offset is the position (in bytes) where the pixel data start nbytespp = number of bytes per pixel type can be int or float (4 bytes pp) or double (8 bytes pp) signed: normally signed data 'y', but 'n' to try to get back the right numbers when unsigned data are converted to signed (python once had no unsigned numeric types.) swap, normally do not bother, but 'y' to swap bytes typeout is the numpy type to output, normally uint16, but more if overflows occurred x and y are the pixel dimensions TODO : Read in regions of interest PLEASE LEAVE THE STRANGE INTERFACE ALONE - IT IS USEFUL FOR THE BRUKER FORMAT """ tin = "dunno" length = nbytespp * x * y # bytes per pixel times number of pixels if datatype in ['float', 'double']: signed = 'y' key = (datatype, signed, nbytespp) try: tin = DATATYPES[key] except: logging.warning("datatype,signed,nbytespp " + str(key)) raise Exception("Unknown combination of types to readbytestream") # Did we get a string (filename) or a readable stream object? if hasattr(fil, "read") and hasattr(fil, "seek"): infile = fil opened = False else: infile = open(fil, 'rb') opened = True infile.seek(offset) arr = numpy.array(numpy.reshape( numpy.fromstring( infile.read(length), tin) , (x, y)), typeout) if swap == 'y': arr = arr.byteswap() if opened: infile.close() return arr