automatic roi selector based on automatic scale selection fixed at single point

roi_selector_pyr.py

"""
author : Peb Ruswono Aryan
Automatic selection of ROI rectangle based on single point (assumed target center) selection on the image 
Automatic scale selection performed by selecting scale which maximizes laplacian of gaussian in the selected point across scales
intended use : simplifying object tracking target selection, output rectangle can be used as initial target
"""
import os
import sys
import cv2
import numpy as np
from math import floor, ceil

def find_optimal_window(img, x, y):
    STEP = 6
    BASE = 3

    pyr = [img]
    pt = (x,y)
    pts = [(1.*pt[0], 1.*pt[1])]
    val = [sample_point(LoG(pyr[0]), pts[0][0], pts[0][1])]
    w = [BASE]

    for i in range(STEP):
        pyr.append(cv2.pyrDown(pyr[-1]))
        pts.append((pts[-1][0]*0.5, pts[-1][1]*0.5))
        val.append(sample_point(LoG(pyr[i+1]), pts[i+1][0], pts[i+1][1]))
        w.append(w[-1]*2)

    return w[np.argmax(np.abs(np.array(val)))]


def mouseHandler(e, x, y, flags, params):
    global img
    if e == cv2.EVENT_LBUTTONDOWN:
        optimal_width = find_optimal_window(gr, x, y)
        mid = optimal_width / 2
        imc = img.copy()
        cv2.circle(imc, (x, y), 1, (0,255,255))
        cv2.rectangle(imc, (int(x-mid), int(y-mid)), (int(x+mid), int(y+mid)), (0,255,255))

        cv2.imshow("select", imc)

def sample_point(img, x, y):
    x1 = int(floor(x))
    y1 = int(floor(y))
    x2 = int(ceil(x))
    y2 = int(ceil(y))

    v1 = img[y1,x1]
    v2 = img[y1,x2]
    v3 = img[y2,x1]
    v4 = img[y2,x2]

    alpha = x-x1
    beta = y-y1

    vh1 = v1 * (1.-alpha) + v2 * (alpha)
    vh2 = v3 * (1.-alpha) + v4 * (alpha)
    return vh1 * (1.-beta) + vh2 * (beta)

def LoG(img):
    G = cv2.GaussianBlur(img, (3,3), 2)
    L = cv2.Laplacian(G, cv2.CV_32F)
    return L

if __name__=="__main__":
    fn = "warna.jpg"
    if len(sys.argv)>1 and os.path.exists(sys.argv[1]):
        fn = sys.argv[1]    
    cv2.namedWindow("select")
    cv2.setMouseCallback("select", mouseHandler, None)

    img = cv2.imread(fn)
    gr = cv2.cvtColor(img, cv2.COLOR_BGR2GRAY) 
    cv2.imshow("select", img)
    while True:
        k = cv2.waitKey(1)
        if k == 27 or k == ord('q'):
            break
    cv2.destroyAllWindows()

sample_point is not working