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# --------------------------------------------------------
# SiamMask
# Licensed under The MIT License
# Written by Qiang Wang (wangqiang2015 at ia.ac.cn)
# --------------------------------------------------------
import numpy as np
import math
from SiamMask.utils.bbox_helper import center2corner, corner2center
class Anchors:
def __init__(self, cfg):
self.stride = 8
self.ratios = [0.33, 0.5, 1, 2, 3]
self.scales = [8]
self.round_dight = 0
self.image_center = 0
self.size = 0
self.anchor_density = 1
self.__dict__.update(cfg)
self.anchor_num = len(self.scales) * len(self.ratios) * (self.anchor_density**2)
self.anchors = None # in single position (anchor_num*4)
self.all_anchors = None # in all position 2*(4*anchor_num*h*w)
self.generate_anchors()
def generate_anchors(self):
self.anchors = np.zeros((self.anchor_num, 4), dtype=np.float32)
size = self.stride * self.stride
count = 0
anchors_offset = self.stride / self.anchor_density
anchors_offset = np.arange(self.anchor_density)*anchors_offset
anchors_offset = anchors_offset - np.mean(anchors_offset)
x_offsets, y_offsets = np.meshgrid(anchors_offset, anchors_offset)
for x_offset, y_offset in zip(x_offsets.flatten(), y_offsets.flatten()):
for r in self.ratios:
if self.round_dight > 0:
ws = round(math.sqrt(size*1. / r), self.round_dight)
hs = round(ws * r, self.round_dight)
else:
ws = int(math.sqrt(size*1. / r))
hs = int(ws * r)
for s in self.scales:
w = ws * s
h = hs * s
self.anchors[count][:] = [-w*0.5+x_offset, -h*0.5+y_offset, w*0.5+x_offset, h*0.5+y_offset][:]
count += 1
def generate_all_anchors(self, im_c, size):
if self.image_center == im_c and self.size == size:
return False
self.image_center = im_c
self.size = size
a0x = im_c - size // 2 * self.stride
ori = np.array([a0x] * 4, dtype=np.float32)
zero_anchors = self.anchors + ori
x1 = zero_anchors[:, 0]
y1 = zero_anchors[:, 1]
x2 = zero_anchors[:, 2]
y2 = zero_anchors[:, 3]
x1, y1, x2, y2 = map(lambda x: x.reshape(self.anchor_num, 1, 1), [x1, y1, x2, y2])
cx, cy, w, h = corner2center([x1, y1, x2, y2])
disp_x = np.arange(0, size).reshape(1, 1, -1) * self.stride
disp_y = np.arange(0, size).reshape(1, -1, 1) * self.stride
cx = cx + disp_x
cy = cy + disp_y
# broadcast
zero = np.zeros((self.anchor_num, size, size), dtype=np.float32)
cx, cy, w, h = map(lambda x: x + zero, [cx, cy, w, h])
x1, y1, x2, y2 = center2corner([cx, cy, w, h])
self.all_anchors = np.stack([x1, y1, x2, y2]), np.stack([cx, cy, w, h])
return True
# if __name__ == '__main__':
# anchors = Anchors(cfg={'stride':16, 'anchor_density': 2})
# anchors.generate_all_anchors(im_c=255//2, size=(255-127)//16+1+8)
# a = 1
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