def get_center_crop_bbox(center_bboxes_in, im_width=None, im_height=None, warning=True, debug=True):
'''
obtain a bbox to crop around a center point
parameters:
center_bboxes_in: a list of 2 or 4 scalar elements, or (N, 2) / (N, 4) numpy array
2 - > [crop_width, crop_height], the center is the image center
4 - > [center_x, center_y, crop_width, crop_height]
im_width/im_height: scalar
outputs:
crop_bboxes: TLHW format, an int64 numpy array with shape of (N, 4)
'''
np_center_bboxes = safe_center_bbox(center_bboxes_in, warning=warning, debug=debug)
if debug: assert iscenterbbox(np_center_bboxes), 'the center bbox does not have a good shape'
if np_center_bboxes.shape[1] == 4: # crop around the given center and width and height
center_x = np_center_bboxes[:, 0]
center_y = np_center_bboxes[:, 1]
crop_width = np_center_bboxes[:, 2]
crop_height = np_center_bboxes[:, 3]
else: # crop around the center of the image
if debug: assert (im_width is not None) and (im_height is not None), 'the image shape should be known when center is not provided'
center_x = np.ceil(im_width / 2)
center_y = np.ceil(im_height / 2)
crop_width = np_center_bboxes[:, 0]
crop_height = np_center_bboxes[:, 1]
xmin = center_x - np.ceil(crop_width / 2)
ymin = center_y - np.ceil(crop_height / 2)
crop_bboxes = np.hstack((xmin.reshape((-1, 1)), ymin.reshape((-1, 1)), crop_width.reshape((-1, 1)), crop_height.reshape((-1, 1))))
crop_bboxes = crop_bboxes.astype('int64')
return crop_bboxes
def safe_center_bbox(input_bbox, warning=True, debug=True):
'''
make sure to copy the center bbox without modifying it and make the dimension to N x 4 or N x 2
parameters:
input_bbox: a list of 4 (2) elements, a listoflist of 4 (2) elements: e.g., [[1,2,3,4], [5,6,7,8]],
a numpy array with shape or (N, 4) or (4, ) or (N, 2) or (2, )
outputs:
np_bboxes: N X 4 (2) numpy array
'''
if islist(input_bbox):
if islistoflist(input_bbox):
if debug:
assert all(
len(list_tmp) == 4 or len(list_tmp) == 2 for list_tmp in
input_bbox), 'all sub-lists should have length of 4'
np_bboxes = np.array(input_bbox)
else:
if debug:
assert len(input_bbox) == 4 or len(
input_bbox
) == 2, 'the center bboxes list does not have a good shape'
if len(input_bbox) == 4:
np_bboxes = np.array(input_bbox).reshape((1, 4))
else:
np_bboxes = np.array(input_bbox).reshape((1, 2))
elif isnparray(input_bbox):
input_bbox = input_bbox.copy()
if input_bbox.shape == (4, ): np_bboxes = input_bbox.reshape((1, 4))
elif input_bbox.shape == (2, ): np_bboxes = input_bbox.reshape((1, 2))
else:
if debug:
assert iscenterbbox(
input_bbox
), 'the input center bbox numpy array does not have a good shape'
np_bboxes = input_bbox
else:
assert False, 'only list and numpy array for bbox are supported'
return np_bboxes