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made center calc centroid

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This commit is contained in:
Thomas Breloff 2016-05-04 21:36:15 -04:00
parent 66bd2559b9
commit e30affdfc2
1 changed files with 20 additions and 1 deletions
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21
src/components.jl
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@ -128,7 +128,26 @@ end
# ----------------------------------------------------------------------- # -----------------------------------------------------------------------
center(shape::Shape) = (mean(shape.x), mean(shape.y)) # center(shape::Shape) = (mean(shape.x), mean(shape.y))
# uses the centroid calculation from https://en.wikipedia.org/wiki/Centroid#Centroid_of_polygon
function center(shape::Shape)
x, y = shape_coords(shape)
n = length(x)
A, Cx, Cy = 0.0, 0.0, 0.0
for i=1:n
ip1 = i==n ? 1 : i+1
A += x[i] * y[ip1] - x[ip1] * y[i]
end
A *= 0.5
for i=1:n
ip1 = i==n ? 1 : i+1
m = (x[i] * y[ip1] - x[ip1] * y[i])
Cx += (x[i] + x[ip1]) * m
Cy += (y[i] + y[ip1]) * m
end
Cx / 6A, Cy / 6A
end
function Base.scale!(shape::Shape, x::Real, y::Real = x, c = center(shape)) function Base.scale!(shape::Shape, x::Real, y::Real = x, c = center(shape))
sx, sy = shape_coords(shape) sx, sy = shape_coords(shape)