Create flowio.py

flowio.py

@@ -0,0 +1,118 @@
+'''
+python by:  youngjung uh, Clova ML, Naver
+contact:    youngjung.uh@navercorp.com
+date:       17 Dec 2018
+
+-------------------------------------------------------------------
+---- below comment came from the original (readFlowFile.m) -------
+---- below comment came from the original (writeFlowFile.m) -------
+-------------------------------------------------------------------
+readFlowFile read a flow file FILENAME into 2-band image IMG
+writeFlowFile writes a 2-band image IMG into flow file FILENAME
+
+  According to the c++ source code of Daniel Scharstein
+  Contact: schar@middlebury.edu
+
+  Author: Deqing Sun, Department of Computer Science, Brown University
+  Contact: dqsun@cs.brown.edu
+  $Date: 2007-10-31 15:36:40 (Wed, 31 Oct 2006) $
+
+Copyright 2007, Deqing Sun.
+
+                        All Rights Reserved
+
+Permission to use, copy, modify, and distribute this software and its
+documentation for any purpose other than its incorporation into a
+commercial product is hereby granted without fee, provided that the
+above copyright notice appear in all copies and that both that
+copyright notice and this permission notice appear in supporting
+documentation, and that the name of the author and Brown University not be used in
+advertising or publicity pertaining to distribution of the software
+without specific, written prior permission.
+
+THE AUTHOR AND BROWN UNIVERSITY DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR ANY
+PARTICULAR PURPOSE.  IN NO EVENT SHALL THE AUTHOR OR BROWN UNIVERSITY BE LIABLE FOR
+ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+'''
+
+import os
+import numpy as np
+from struct import pack, unpack
+
+
+def readFlowFile(fname):
+    '''
+    args
+        fname (str)
+    return
+        flow (numpy array) numpy array of shape (height, width, 2)
+    '''
+
+    TAG_FLOAT = 202021.25  # check for this when READING the file
+
+    ext = os.path.splitext(fname)[1]
+
+    assert len(ext) > 0, ('readFlowFile: extension required in fname %s' % fname)
+    assert ext == '.flo', exit('readFlowFile: fname %s should have extension ''.flo''' % fname)
+
+    try:
+        fid = open(fname, 'rb')
+    except IOError:
+        print('readFlowFile: could not open %s', fname)
+
+    tag     = unpack('f', fid.read(4))[0]
+    width   = unpack('i', fid.read(4))[0]
+    height  = unpack('i', fid.read(4))[0]
+
+    assert tag == TAG_FLOAT, ('readFlowFile(%s): wrong tag (possibly due to big-endian machine?)' % fname)
+    assert 0 < width and width < 100000, ('readFlowFile(%s): illegal width %d' % (fname, width))
+    assert 0 < height and height < 100000, ('readFlowFile(%s): illegal height %d' % (fname, height))
+
+    nBands = 2
+
+    # arrange into matrix form
+    flow = np.fromfile(fid, np.float32)
+    flow = flow.reshape(height, width, nBands)
+
+    fid.close()
+
+    return flow
+
+def writeFlowFile(img, fname):
+    TAG_STRING = 'PIEH'    # use this when WRITING the file
+
+    ext = os.path.splitext(fname)[1]
+
+    assert len(ext) > 0, ('writeFlowFile: extension required in fname %s' % fname)
+    assert ext == '.flo', exit('writeFlowFile: fname %s should have extension ''.flo''', fname)
+
+    height, width, nBands = img.shape
+
+    assert nBands == 2, 'writeFlowFile: image must have two bands'
+
+    try:
+        fid = open(fname, 'wb')
+    except IOError:
+        print('writeFlowFile: could not open %s', fname)
+
+    # write the header
+    # fid.write(TAG_STRING.encode(encoding='utf-8', errors='strict'))
+    # code = unpack('f', bytes(TAG_STRING, 'utf-8'))[0]
+    # fid.write(pack('f', code))
+    fid.write(bytes(TAG_STRING, 'utf-8'))
+    fid.write(pack('i', width))
+    fid.write(pack('i', height))
+
+    # arrange into matrix form
+    tmp = np.zeros((height, width*nBands), np.float32)
+
+    tmp[:, np.arange(width) * nBands] = img[:, :, 0]
+    tmp[:, np.arange(width) * nBands + 1] = np.squeeze(img[:, :, 1])
+
+    fid.write(bytes(tmp))
+
+    fid.close()