81 lines
2.8 KiB
Python
81 lines
2.8 KiB
Python
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import math
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import numpy
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import scipy.ndimage
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import imagecodecs
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import imreg
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from matplotlib import pyplot, patches
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def brute_force_scale_invariant_template_matching(
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template, # grayscale image
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search, # scaled and cropped grayscale image
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zooms=(1.0, 0.5, 0.25), # sequence of zoom factors to try
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size=None, # power-of-two size of square sliding window
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delta=None, # advance of sliding windows. default: half window size
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min_overlap=0.25, # minimum overlap of search with window
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max_diff=0.05, # max average of search - window differences in overlap
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max_angle=0.5, # no rotation
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):
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"""Return yoffset, xoffset, and scale of first match of search in template.
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Iterate over scaled versions of the template image in overlapping sliding
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windows and run FFT-based algorithm for translation, rotation and
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scale-invariant image registration until a match of the search image is
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found in the sliding window.
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"""
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if size is None:
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size = int(pow(2, int(math.log(min(search.shape), 2))))
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if delta is None:
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delta = size // 2
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search = search[:size, :size]
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for zoom in zooms:
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windows = numpy.lib.stride_tricks.sliding_window_view(
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scipy.ndimage.zoom(template, zoom), search.shape
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)[::delta, ::delta]
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for i in range(windows.shape[0]):
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for j in range(windows.shape[1]):
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print('.', end='')
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window = windows[i, j]
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im2, scale, angle, (t0, t1) = imreg.similarity(window, search)
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diff = numpy.abs(im2 - window)[im2 != 0]
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if (
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abs(angle) < max_angle
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and diff.size / window.size > min_overlap
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and numpy.mean(diff) < max_diff
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):
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return (
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(i * delta - t0) / zoom,
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(j * delta - t1) / zoom,
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1 / scale / zoom,
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)
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raise ValueError('no match of search image found in template')
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def rgb2gray(rgb, scale=None):
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"""Return float grayscale image from RGB24 or RGB48 image."""
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scale = numpy.iinfo(rgb.dtype).max if scale is None else scale
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scale = numpy.array([[[0.299, 0.587, 0.114]]], numpy.float32) / scale
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return numpy.sum(rgb * scale, axis=-1)
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template = imagecodecs.imread('cw1_IMG_9037.jpg')
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search = imagecodecs.imread('cw1_p1_9037_kzw.jpg')
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yoffset, xoffset, scale = brute_force_scale_invariant_template_matching(
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rgb2gray(template), rgb2gray(search), zooms=(0.5,)
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)
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print(yoffset, xoffset, scale)
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figure, ax = pyplot.subplots()
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ax.imshow(template)
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rect = patches.Rectangle(
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(xoffset, yoffset),
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scale * search.shape[1],
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scale * search.shape[0],
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linewidth=1,
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edgecolor='r',
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facecolor='none',
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)
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ax.add_patch(rect)
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pyplot.show()
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