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105 lines
3.0 KiB
105 lines
3.0 KiB
# --------------------------------------------------------
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# Faster R-CNN
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# Copyright (c) 2015 Microsoft
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# Licensed under The MIT License [see LICENSE for details]
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# Written by Ross Girshick and Sean Bell
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# --------------------------------------------------------
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import numpy as np
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# Verify that we compute the same anchors as Shaoqing's matlab implementation:
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#
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# >> load output/rpn_cachedir/faster_rcnn_VOC2007_ZF_stage1_rpn/anchors.mat
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# >> anchors
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#
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# anchors =
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#
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# -83 -39 100 56
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# -175 -87 192 104
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# -359 -183 376 200
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# -55 -55 72 72
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# -119 -119 136 136
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# -247 -247 264 264
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# -35 -79 52 96
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# -79 -167 96 184
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# -167 -343 184 360
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#array([[ -83., -39., 100., 56.],
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# [-175., -87., 192., 104.],
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# [-359., -183., 376., 200.],
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# [ -55., -55., 72., 72.],
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# [-119., -119., 136., 136.],
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# [-247., -247., 264., 264.],
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# [ -35., -79., 52., 96.],
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# [ -79., -167., 96., 184.],
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# [-167., -343., 184., 360.]])
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def generate_anchors(base_size=16, ratios=[0.5, 1, 2],
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scales=2**np.arange(3, 6)):
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"""
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Generate anchor (reference) windows by enumerating aspect ratios X
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scales wrt a reference (0, 0, 15, 15) window.
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"""
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base_anchor = np.array([1, 1, base_size, base_size]) - 1
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ratio_anchors = _ratio_enum(base_anchor, ratios)
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anchors = np.vstack([_scale_enum(ratio_anchors[i, :], scales)
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for i in range(ratio_anchors.shape[0])])
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return anchors
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def _whctrs(anchor):
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"""
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Return width, height, x center, and y center for an anchor (window).
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"""
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w = anchor[2] - anchor[0] + 1
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h = anchor[3] - anchor[1] + 1
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x_ctr = anchor[0] + 0.5 * (w - 1)
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y_ctr = anchor[1] + 0.5 * (h - 1)
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return w, h, x_ctr, y_ctr
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def _mkanchors(ws, hs, x_ctr, y_ctr):
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"""
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Given a vector of widths (ws) and heights (hs) around a center
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(x_ctr, y_ctr), output a set of anchors (windows).
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"""
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ws = ws[:, np.newaxis]
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hs = hs[:, np.newaxis]
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anchors = np.hstack((x_ctr - 0.5 * (ws - 1),
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y_ctr - 0.5 * (hs - 1),
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x_ctr + 0.5 * (ws - 1),
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y_ctr + 0.5 * (hs - 1)))
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return anchors
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def _ratio_enum(anchor, ratios):
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"""
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Enumerate a set of anchors for each aspect ratio wrt an anchor.
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"""
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w, h, x_ctr, y_ctr = _whctrs(anchor)
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size = w * h
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size_ratios = size / ratios
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ws = np.round(np.sqrt(size_ratios))
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hs = np.round(ws * ratios)
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anchors = _mkanchors(ws, hs, x_ctr, y_ctr)
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return anchors
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def _scale_enum(anchor, scales):
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"""
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Enumerate a set of anchors for each scale wrt an anchor.
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"""
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w, h, x_ctr, y_ctr = _whctrs(anchor)
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ws = w * scales
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hs = h * scales
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anchors = _mkanchors(ws, hs, x_ctr, y_ctr)
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return anchors
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#if __name__ == '__main__':
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# import time
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# t = time.time()
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# a = generate_anchors()
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# print time.time() - t
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# print a
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# from IPython import embed; embed()
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