frame_grabber.py

# Daniel B. Allan
# August 2014
# Robert L. Leheny Lab, JHU Dept. of Physics & Astronomy

"""
Capture an image from a NI frame grabber.

Adapted from code posted by Oliver W. at
http://stackoverflow.com/questions/17095359

This assumes a monochromatic camera. See the source link
for discussion on capturing color images (some code for
which remains, unused, in this implementation).

This is tested on an NI PCIe-1433 running LabView 2014
on Windows 7 32-bit with an IO Industries Flare 4M camera.
"""

from __future__ import division, print_function

import ctypes as C
import ctypes.util as Cutil
import time

imgbuffer = None
imgbuffer_vpp = None


# useful references:
# location of the niimaq.h: C:\Program Files (x86)\National Instruments\NI-IMAQ\Include
# location of the camera files: C:\Users\Public\Documents\National Instruments\NI-IMAQ\Data
# check it C:\Users\Public\Documents\National Instruments\NI-IMAQ\Examples\MSVC\Color\BayerDecode

class IMAQError(Exception):
    """A class for errors produced during the calling of National Intrument's IMAQ functions.
    It will also produce the textual error message that corresponds to a specific code."""

    def __init__(self, code):
        self.code = code
        text = C.c_char_p('')
        imaq.imgShowError(code, text)
        self.message = "{}: {}".format(self.code, text.value)
        # Call the base class constructor with the parameters it needs
        Exception.__init__(self, self.message)


def imaq_error_handler(code):
    """Print the textual error message that is associated with the error code."""

    if code < 0:
        raise IMAQError(code)
        free_associated_resources = 1
        imaq.imgSessionStopAcquisition(sid)
        imaq.imgClose(sid, free_associated_resources)
        imaq.imgClose(iid, free_associated_resources)
    else:
        return code
        
imaqlib_path = Cutil.find_library('imaq')
imaq = C.windll.LoadLibrary(imaqlib_path)

imaq_function_list = [  # this is not an exhaustive list, merely the ones used in this program
    imaq.imgGetAttribute,
    imaq.imgInterfaceOpen,
    imaq.imgSessionOpen,
    imaq.niimaquDisable32bitPhysMemLimitEnforcement,  # because we're running on a 64-bit machine with over 3GB of RAM
    imaq.imgCreateBufList,
    imaq.imgCreateBuffer,
    imaq.imgSetBufferElement,
    imaq.imgSnap,
    imaq.imgSessionSaveBufferEx,
    imaq.imgSessionStopAcquisition,
    imaq.imgClose,
    imaq.imgCalculateBayerColorLUT,
    imaq.imgBayerColorDecode ]

# for all imaq functions we're going to call, we should specify that if they
# produce an error (a number), we want to see the error message (textually)
for func in imaq_function_list:
    func.restype = imaq_error_handler


def initialize(interface_name='img0'):
    global imgbuffer
    global imgbuffer_vpp
    
    INTERFACE_ID = C.c_uint32
    SESSION_ID = C.c_uint32
    BUFLIST_ID = C.c_uint32
    iid = INTERFACE_ID(0)
    sid = SESSION_ID(0)
    bid = BUFLIST_ID(0)
    array_16bit = 2**16 * C.c_uint32
    redLUT, greenLUT, blueLUT  = [ array_16bit() for _ in range(3) ]
    
    red_gain, blue_gain, green_gain = [ C.c_double(val) for val in (1., 1., 1.) ]
    # OPEN A COMMUNICATION CHANNEL WITH THE CAMERA
    # our camera has been given its proper name in Measurement & Automation Explorer (MAX)
    imaq.imgInterfaceOpen(interface_name, C.byref(iid))
    imaq.imgSessionOpen(iid, C.byref(sid)); 

    # START C MACROS DEFINITIONS
    # define some C preprocessor macros (these are all defined in the niimaq.h file)
    _IMG_BASE = 0x3FF60000

    IMG_BUFF_ADDRESS = _IMG_BASE + 0x007E  # void *
    IMG_BUFF_COMMAND = _IMG_BASE + 0x007F  # uInt32
    IMG_BUFF_SIZE = _IMG_BASE + 0x0082  #uInt32
    IMG_CMD_STOP = 0x08  # single shot acquisition

    IMG_ATTR_ROI_WIDTH = _IMG_BASE + 0x01A6
    IMG_ATTR_ROI_HEIGHT = _IMG_BASE + 0x01A7
    IMG_ATTR_BYTESPERPIXEL = _IMG_BASE + 0x0067  
    IMG_ATTR_COLOR = _IMG_BASE + 0x0003  # true = supports color
    IMG_ATTR_PIXDEPTH = _IMG_BASE + 0x0002  # pix depth in bits
    IMG_ATTR_BITSPERPIXEL = _IMG_BASE + 0x0066 # aka the bit depth

    IMG_BAYER_PATTERN_GBGB_RGRG = 0
    IMG_BAYER_PATTERN_GRGR_BGBG = 1
    IMG_BAYER_PATTERN_BGBG_GRGR = 2
    IMG_BAYER_PATTERN_RGRG_GBGB = 3
    # END C MACROS DEFINITIONS

    width, height = C.c_uint32(), C.c_uint32()
    has_color, pixdepth, bitsperpixel, bytes_per_pixel = [ C.c_uint8() for _ in range(4) ]

    # poll the camera (or is it the camera file (icd)?) for these attributes and store them in the variables
    for var, macro in [ (width, IMG_ATTR_ROI_WIDTH), 
                        (height, IMG_ATTR_ROI_HEIGHT),
                        (bytes_per_pixel, IMG_ATTR_BYTESPERPIXEL),
                        (pixdepth, IMG_ATTR_PIXDEPTH),
                        (has_color, IMG_ATTR_COLOR),
                        (bitsperpixel, IMG_ATTR_BITSPERPIXEL) ]:
        imaq.imgGetAttribute(sid, macro, C.byref(var))  


    print("Image ROI size: {} x {}".format(width.value, height.value))
    print("Pixel depth: {}\nBits per pixel: {} -> {} bytes per pixel".format(
        pixdepth.value, 
        bitsperpixel.value, 
        bytes_per_pixel.value))

    bufsize = width.value*height.value*bytes_per_pixel.value
    imaq.niimaquDisable32bitPhysMemLimitEnforcement(sid)

    # create the buffer (in a list)
    imaq.imgCreateBufList(1, C.byref(bid))  # Creates a buffer list with one buffer

    # CONFIGURE THE PROPERTIES OF THE BUFFER
    imgbuffer = C.POINTER(C.c_uint16)()  # create a null pointer
    RGBbuffer = C.POINTER(C.c_uint32)()  # placeholder for the Bayer decoded imgbuffer (i.e. demosaiced imgbuffer)
    imaq.imgCreateBuffer(sid, 0, bufsize, C.byref(imgbuffer))  # allocate memory (the buffer) on the host machine (param2==0)
    imaq.imgCreateBuffer(sid, 0, width.value*height.value * 4, C.byref(RGBbuffer))

    imaq.imgSetBufferElement(bid, 0, IMG_BUFF_ADDRESS, C.cast(imgbuffer, C.POINTER(C.c_uint32)))  # my guess is that the cast to an uint32 is necessary to prevent 64-bit callable memory addresses
    imaq.imgSetBufferElement(bid, 0, IMG_BUFF_SIZE, bufsize)
    imaq.imgSetBufferElement(bid, 0, IMG_BUFF_COMMAND, IMG_CMD_STOP)

    # CALCULATE THE LOOKUP TABLES TO CONVERT THE BAYER ENCODED IMAGE TO RGB (=DEMOSAICING)
    imaq.imgCalculateBayerColorLUT(red_gain, green_gain, blue_gain, redLUT, greenLUT, blueLUT, bitsperpixel)
    imgbuffer_vpp = C.cast(C.byref(imgbuffer), C.POINTER(C.c_void_p))

def capture(filename):
    imaq.imgSnap(sid, imgbuffer_vpp)
    #imaq.imgSnap(sid, imgbuffer)  # <- doesn't work (img produced is entirely black). The above 2 lines are required
    imaq.imgSessionSaveBufferEx(sid, imgbuffer, filename)