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Filter too small segments in coco converter #321

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merged 2 commits into from
Apr 1, 2019
Merged

Filter too small segments in coco converter #321

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1b0b456
Add filtering of small segments
Feb 13, 2019
5062a32
Add polygon-area-threshold command line argument
Feb 18, 2019
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20 changes: 15 additions & 5 deletions utils/coco/converter.py
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Original file line number Diff line number Diff line change
Expand Up @@ -49,14 +49,19 @@ def parse_args():
'--use_background_label', action='store_true',
help='insert in output annotation objects with label \'background\'. By default is false'
)
parser.add_argument(
'--polygon-area-threshold', type=int, default=1,
help='polygons with area less than this value will be ignored. By default set to 1'
)
return parser.parse_args()


def mask_to_polygon(mask, tolerance=1.0):
def mask_to_polygon(mask, tolerance=1.0, area_threshold=1):
"""Convert object's mask to polygon [[x1,y1, x2,y2 ...], [...]]
Args:
mask: object's mask presented as 2D array of 0 and 1
tolerance: maximum distance from original points of polygon to approximated
area_threshold: if area of a polygon is less than this value, remove this small object
"""
polygons = []
# pad mask with 0 around borders
Expand All @@ -77,7 +82,11 @@ def mask_to_polygon(mask, tolerance=1.0):
for i in range(0, len(reshaped_contour)):
if reshaped_contour[i] < 0:
reshaped_contour[i] = 0
polygons.append(reshaped_contour)
# Check if area of a polygon is enough
rle = mask_util.frPyObjects([reshaped_contour], mask.shape[0], mask.shape[1])
area = mask_util.area(rle)
if sum(area) > area_threshold:
polygons.append(reshaped_contour)
return polygons

def draw_polygons(polygons, img_name, input_dir, output_dir, draw_labels):
Expand Down Expand Up @@ -115,7 +124,7 @@ def draw_polygons(polygons, img_name, input_dir, output_dir, draw_labels):
cv2.imwrite(output_file, img)

def fix_segments_intersections(polygons, height, width, img_name, use_background_label,
threshold=0.0, ratio_tolerance=0.001):
threshold=0.0, ratio_tolerance=0.001, area_threshold=1):
"""Find all intersected regions and crop contour for back object by objects which
are in front of the first one. It is related to a specialty of segmentation
in CVAT annotation. Intersection is calculated via function 'iou' from cocoapi
Expand Down Expand Up @@ -175,7 +184,7 @@ def fix_segments_intersections(polygons, height, width, img_name, use_background

bottom_mask = np.sum(bottom_mask, axis=2)
bottom_mask = np.array(bottom_mask > 0, dtype=np.uint8)
converted_polygons[i]['points'] = mask_to_polygon(bottom_mask)
converted_polygons[i]['points'] = mask_to_polygon(bottom_mask, area_threshold=area_threshold)
# If some segment is empty, do small fix to avoid error in cocoapi function
if len(converted_polygons[i]['points']) == 0:
converted_polygons[i]['points'] = [empty_polygon]
Expand Down Expand Up @@ -402,7 +411,8 @@ def main():
height = result_annotation['images'][-1]['height']
width = result_annotation['images'][-1]['width']
image['polygon'] = fix_segments_intersections(image['polygon'], height, width,
image['name'], args.use_background_label)
image['name'], args.use_background_label,
area_threshold=args.polygon_area_threshold)

# Create new annotation for this image
for poly in image['polygon']:
Expand Down