Voronoi.py

''' Estimates bounding boxes of bird parts
    given coordinates. Python prototype.
    To be placed at same level as parts/.
    Note: bird parts are described in parts/parts.txt.
    Use:
        python BirdBox.py 0 test0.bb
    to write bounding boxes for image 0 into `test0.bb`
'''

def intersect(*boxes):
    return tuple(m(b[2*i+axis] for b in boxes) for i,m in enumerate((max,min)) for axis in range(2))
def join(*boxes):
    return tuple(m(b[2*i+axis] for b in boxes) for i,m in enumerate((min,max)) for axis in range(2))

from math import sqrt
distance = lambda a,b: sqrt(sum((aa-bb)**2 for aa,bb in zip(a,b)))
def averagebox(points):
    return join(*[p+p for p in points])
def guess_bounding_boxes(bounding_box, keypoints, N=30):
    ''' Estimates bounding boxes of bird parts
        given coordinates. Inputs:
           `keypoints`, a length-15 list of (y,x) tuples each
           representing the hand-keyed center of a bird part.
           `bounding_box`, a (min_y, min_x, max_y, max_x) tuple
           representing a hand-keyed bounding box for the whole bird.
        Works by estimating Voronoi diagram (currently with an inefficient
        and approximate hack).
    '''
    x,y,X,Y = bounding_box
    coordinates = [((float(xx)/N)*(X-x)+x, (float(yy)/N)*(Y-y)+y) for xx in range(N+1) for yy in range(N+1)]
    domains = {p:[p] for p in keypoints}
    for q in coordinates:
        pp = min((distance(p,q),p) for p in keypoints if q is not p and sum(p))[1]
        domains[pp].append(q)
    return [intersect(bounding_box, averagebox(domains[p])) if sum(p) else (0,0,0,0) for p in keypoints]

import sys
tocoor = lambda line: tuple(float(w) for w in line if w)
tostring = lambda box: ' '.join(str(c) for c in box)
if __name__=='__main__':
    imageid=int(sys.argv[1]); bounding_boxes_name=sys.argv[2]
    with open('bounding_boxes.txt') as f:
        x,y,w,h = tocoor(f.read().split('\n')[imageid].split()[1:])
        bounding_box = y,x,y+h,x+w
    with open('parts/part_locs.txt') as f:
        keypoints = [tocoor(line.split()[2:4])[::-1] for line in f.read().split('\n')[15*imageid:15*(imageid+1)]]
    bounding_boxes = guess_bounding_boxes(bounding_box, keypoints)
    with open(bounding_boxes_name,'w') as f:
        f.write('\n'.join(tostring(box) for box in bounding_boxes))