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# Module 'rect'.
#
# Operations on rectangles.
# There is some normalization: all results return the object 'empty'
# if their result would contain no points.
# Exception.
#
error = 'rect.error'
# The empty rectangle.
#
empty = (0, 0), (0, 0)
# Check if a rectangle is empty.
#
def is_empty(r):
(left, top), (right, bottom) = r
return left >= right or top >= bottom
# Compute the intersection or two or more rectangles.
# This works with a list or tuple argument.
#
def intersect(list):
if not list: raise error, 'intersect called with empty list'
if is_empty(list[0]): return empty
(left, top), (right, bottom) = list[0]
for rect in list[1:]:
if is_empty(rect):
return empty
(l, t), (r, b) = rect
if left < l: left = l
if top < t: top = t
if right > r: right = r
if bottom > b: bottom = b
if is_empty(((left, top), (right, bottom))):
return empty
return (left, top), (right, bottom)
# Compute the smallest rectangle containing all given rectangles.
# This works with a list or tuple argument.
#
def union(list):
(left, top), (right, bottom) = list[0]
for (l, t), (r, b) in list[1:]:
if not is_empty(((l, t), (r, b))):
if l < left: left = l
if t < top: top = t
if r > right: right = r
if b > bottom: bottom = b
res = (left, top), (right, bottom)
if is_empty(res):
return empty
return res
# Check if a point is in a rectangle.
#
def pointinrect((h, v), ((left, top), (right, bottom))):
return left <= h < right and top <= v < bottom
# Return a rectangle that is dh, dv inside another
#
def inset(((left, top), (right, bottom)), (dh, dv)):
left = left + dh
top = top + dv
right = right - dh
bottom = bottom - dv
r = (left, top), (right, bottom)
if is_empty(r):
return empty
else:
return r
# Conversions between rectangles and 'geometry tuples',
# given as origin (h, v) and dimensions (width, height).
#
def rect2geom((left, top), (right, bottom)):
return (left, top), (right-left, bottom-top)
def geom2rect((h, v), (width, height)):
return (h, v), (h+width, v+height)
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