opencv/samples/python2/browse.py

'''
browse.py shows how to implement a simple hi resolution image navigation
'''

import numpy as np
import cv2
import sys

print 'This sample shows how to implement a simple hi resolution image navigation.'
print 'USAGE: browse.py [image filename]'
print 

if len(sys.argv) > 1:
    fn = sys.argv[1]
    print 'loading %s ...' % fn
    img = cv2.imread(fn)
else:
    sz = 4096
    print 'generating %dx%d procedural image ...' % (sz, sz)
    img = np.zeros((sz, sz), np.uint8)
    track = np.cumsum(np.random.rand(500000, 2)-0.5, axis=0)
    track = np.int32(track*10 + (sz/2, sz/2))
    cv2.polylines(img, [track], 0, 255, 1, cv2.CV_AA)

small = img
for i in xrange(3):
    small = cv2.pyrDown(small)

def onmouse(event, x, y, flags, param):
    h, w = img.shape[:2]
    h1, w1 = small.shape[:2]
    x, y = 1.0*x*h/h1, 1.0*y*h/h1
    zoom = cv2.getRectSubPix(img, (800, 600), (x+0.5, y+0.5))
    cv2.imshow('zoom', zoom)

cv2.imshow('preview', small)
cv2.setMouseCallback('preview', onmouse)
cv2.waitKey()