def detector_postprocess(results,
output_height,
output_width,
mask_threshold=0.5):
"""
Resize the output instances.
The input images are often resized when entering an object detector.
As a result, we often need the outputs of the detector in a different
resolution from its inputs.
This function will resize the raw outputs of an R-CNN detector
to produce outputs according to the desired output resolution.
Args:
results (Instances): the raw outputs from the detector.
`results.image_size` contains the input image resolution the detector sees.
This object might be modified in-place.
output_height, output_width: the desired output resolution.
Returns:
Instances: the resized output from the model, based on the output resolution
"""
scale_x, scale_y = (output_width / results.image_size[1],
output_height / results.image_size[0])
results = Instances((output_height, output_width), **results.get_fields())
if results.has("pred_boxes"):
output_boxes = results.pred_boxes
elif results.has("proposal_boxes"):
output_boxes = results.proposal_boxes
output_boxes.scale(scale_x, scale_y)
output_boxes.clip(results.image_size)
results = results[output_boxes.nonempty()]
if results.has("pred_masks"):
results.pred_masks = paste_masks_in_image(
results.pred_masks[:, 0, :, :], # N, 1, M, M
results.pred_boxes,
results.image_size,
threshold=mask_threshold,
)
if results.has("pred_keypoints"):
results.pred_keypoints[:, :, 0] *= scale_x
results.pred_keypoints[:, :, 1] *= scale_y
return results
def _paste_mask_lists_in_image(masks, boxes, image_shape, threshold=0.5):
"""
Paste a list of masks that are of various resolutions (e.g., 28 x 28) into an image.
The location, height, and width for pasting each mask is determined by their
corresponding bounding boxes in boxes.
Args:
masks (list(Tensor)): A list of Tensor of shape (1, Hmask_i, Wmask_i).
Values are in [0, 1]. The list length, Bimg, is the
number of detected object instances in the image.
boxes (Boxes): A Boxes of length Bimg. boxes.tensor[i] and masks[i] correspond
to the same object instance.
image_shape (tuple): height, width
threshold (float): A threshold in [0, 1] for converting the (soft) masks to
binary masks.
Returns:
img_masks (Tensor): A tensor of shape (Bimg, Himage, Wimage), where Bimg is the
number of detected object instances and Himage, Wimage are the image width
and height. img_masks[i] is a binary mask for object instance i.
"""
if len(masks) == 0:
return torch.empty((0, 1) + image_shape, dtype=torch.uint8)
# Loop over masks groups. Each group has the same mask prediction size.
img_masks = []
ind_masks = []
mask_sizes = torch.tensor([m.shape[-1] for m in masks])
unique_sizes = torch.unique(mask_sizes)
for msize in unique_sizes.tolist():
cur_ind = torch.where(mask_sizes == msize)[0]
ind_masks.append(cur_ind)
cur_masks = cat([masks[i] for i in cur_ind])
cur_boxes = boxes[cur_ind]
img_masks.append(
paste_masks_in_image(cur_masks, cur_boxes, image_shape, threshold)
)
img_masks = cat(img_masks)
ind_masks = cat(ind_masks)
img_masks_out = torch.empty_like(img_masks)
img_masks_out[ind_masks, :, :] = img_masks
return img_masks_out