Function writeFloFlow

datasets_preprocess/flow_IO.py:136–179

write optical flow in .flo format to file as used in the Sintel dataset (Butler et al., 2012) flow: optical flow with shape height x width x 2 filepath: optical flow file path to be saved --- ".flo" file format used for optical flow evaluation Stores 2-band float image for

(flow, filepath)

def writeFloFlow(flow, filepath):
    """
    write optical flow in .flo format to file as used in the Sintel dataset (Butler et al., 2012)
    flow: optical flow with shape height x width x 2
    filepath: optical flow file path to be saved
    ---
    ".flo" file format used for optical flow evaluation

    Stores 2-band float image for horizontal (u) and vertical (v) flow components.
    Floats are stored in little-endian order.
    A flow value is considered "unknown" if either |u| or |v| is greater than 1e9.

    bytes  contents

    0-3     tag: "PIEH" in ASCII, which in little endian happens to be the float 202021.25
            (just a sanity check that floats are represented correctly)
    4-7     width as an integer
    8-11    height as an integer
    12-end  data (width*height*2*4 bytes total)
            the float values for u and v, interleaved, in row order, i.e.,
            u[row0,col0], v[row0,col0], u[row0,col1], v[row0,col1], ...
    """

    height, width, nBands = flow.shape

    with open(filepath, "wb") as f:
        if f is None:
            raise IOError(f"write flo file {filepath}: file could not be opened")

        # write header
        result = f.write(FLO_TAG_STRING.encode("ascii"))
        result += f.write(struct.pack("i", width))
        result += f.write(struct.pack("i", height))
        if result != 12:
            raise IOError(f"write flo file {filepath}: problem writing header")

        # write content
        n = nBands * width
        for i in range(height):
            data = flow[i, :, :].flatten()
            data[np.isnan(data)] = FLO_UNKNOWN_FLOW
            result = f.write(struct.pack(f"{n}f", *data))
            if result != n * 4:
                raise IOError(f"write flo file {filepath}: problem writing row {i}")


def readPngFlow(filepath):