12.1.10.2.1. Cross correlation of images

In this demo the cross-correlation is calculated between two images acquired via the integrated webcam of your PC.

Can not open camera with OpenCVGrabber. Probabel root cause: WebCam is not available.
Used Itom Dummy Grabber instead.

from itom import dataIO
from itom import dataObject
from itom import ui
import numpy as np
from numpy import fft


# some methods
def acquireImage1():
    g = cam.getAutoGrabbing()
    cam.setAutoGrabbing(False)
    cam.acquire()
    cam.copyVal(image1)
    gui.plot1["source"] = image1
    cam.setAutoGrabbing(g)


def acquireImage2():
    g = cam.getAutoGrabbing()
    cam.setAutoGrabbing(False)
    cam.acquire()
    cam.copyVal(image2)
    gui.plot2["source"] = image2
    cam.setAutoGrabbing(g)


def evaluate():
    """determines the offset between image1 and image2
    using cross-correlation and returns a tuple containing
    the shift in x and y-direction"""

    npImg1 = np.array(image1)
    npImg2 = np.array(image2)

    npImg1FFT = fft.fft2(npImg1)
    npImg2FFT = fft.fft2(npImg2)
    ccr = fft.ifft2(npImg1FFT * npImg2FFT.conj())
    ccr_abs = np.abs(ccr)  # np.ascontiguousarray(np.abs(ccr))

    [m, n] = ccr_abs.shape
    max_pos = np.argmax(ccr_abs)
    offset_x = max_pos % n
    offset_y = (max_pos - offset_x) / n

    if offset_x > n / 2:
        offset_x = offset_x - n
    if offset_y > m / 2:
        offset_y = offset_y - m

    gui.lbl_dx["text"] = "dx: " + str(offset_x)
    gui.lbl_dy["text"] = "dy: " + str(offset_y)


def saveImages():
    filename = ui.getSaveFileName("Filename", filters="IDC (*.idc)", parent=gui)
    if filename:
        saveIDC(filename, {"image1": image1, "image2": image2})


def loadImages():
    global image1
    global image2
    filename = ui.getOpenFileName("Filename", filters="IDC (*idc)", parent=gui)
    if filename:
        d = loadIDC(filename)
        image1 = d["image1"]
        image2 = d["image2"]
        gui.plot1["source"] = image1
        gui.plot2["source"] = image2


# open camera (make it before you start this script)
try:
    cam = dataIO("OpenCVGrabber", colorMode="gray")
except:
    print("Can not open camera with OpenCVGrabber. Probabel root cause: WebCam is not available.")
    print("Used Itom Dummy Grabber instead.")
    cam = dataIO("DummyGrabber")

# start camera
cam.startDevice()

# create data objects
image1 = dataObject()
image2 = dataObject()

# create gui
gui = ui("dialog.ui", ui.TYPEWINDOW)
gui.btnAcquire1.connect("clicked()", acquireImage1)
gui.btnAcquire2.connect("clicked()", acquireImage2)
gui.btnLoad.connect("clicked()", loadImages)
gui.btnSave.connect("clicked()", saveImages)
gui.btnEval.connect("clicked()", evaluate)

# show live image in upper plot
if cam.name() != "FileGrabber":
    cam.setAutoGrabbing(True)
else:
    cam.setAutoGrabbing(False)

gui.plotLive["camera"] = cam
gui.plotLive["keepAspectRatio"] = True
gui.plotLive["yAxisFlipped"] = True

gui.show()