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libs/lua-math-polygon: add add math lib for gauss jordan Ponit in Polygon algorithm

Signed-off-by: Jan-Tarek Butt <tarek@ring0.de>
pull/222/head
Jan-Tarek Butt 3 years ago
committed by Matthias Schiffer
parent
commit
67177de99a
No known key found for this signature in database GPG Key ID: 16EF3F64CB201D9C
  1. 22
      libs/lua-math-polygon/Makefile
  2. 66
      libs/lua-math-polygon/src/math-polygon.lua

22
libs/lua-math-polygon/Makefile

@ -0,0 +1,22 @@
include $(TOPDIR)/rules.mk
PKG_NAME:=lua-math-polygon
PKG_VERSION:=1
include $(INCLUDE_DIR)/package.mk
define Package/lua-math-polygon
SECTION:=libs
CATEGORY:=Libraries
TITLE:=Polygon math library can also convert 2 point rectangles into polygons
endef
define Build/Compile
endef
define Package/lua-math-polygon/install
$(INSTALL_DIR) $(1)/usr/lib/lua
$(INSTALL_DATA) src/math-polygon.lua $(1)/usr/lib/lua/
endef
$(eval $(call BuildPackage,lua-math-polygon))

66
libs/lua-math-polygon/src/math-polygon.lua

@ -0,0 +1,66 @@
local M = {}
-- Source with pseudocode: https://de.wikipedia.org/wiki/Punkt-in-Polygon-Test_nach_Jordan
-- see also https://en.wikipedia.org/wiki/Point_in_polygon
-- parameters: points A = (x_a, y_a), B = (x_b, y_b), C = (x_c, y_c)
-- return value: −1 if the ray from A to the right bisects the edge [BC] (the lower vortex of [BC]
-- is not seen as part of [BC]);
-- 0 if A is on [BC];
-- +1 else
function M.cross_prod_test(x_a, y_a, x_b, y_b, x_c, y_c)
if y_a == y_b and y_b == y_c then
if (x_b <= x_a and x_a <= x_c) or (x_c <= x_a and x_a <= x_b) then
return 0
end
return 1
end
if not (y_a == y_b and x_a == x_b) then
if y_b > y_c then
-- swap b and c
local h = x_b
x_b = x_c
x_c = h
h = y_b
y_b = y_c
y_c = h
end
if y_a <= y_b or y_a > y_c then
return 1
end
local delta = (x_b-x_a) * (y_c-y_a) - (y_b-y_a) * (x_c-x_a)
if delta > 0 then
return 1
end
if delta < 0 then
return -1
end
end
return 0
end
-- Source with pseudocode: https://de.wikipedia.org/wiki/Punkt-in-Polygon-Test_nach_Jordan
-- see also: https://en.wikipedia.org/wiki/Point_in_polygon
-- let P be a 2D Polygon and Q a 2D Point
-- return value: +1 if Q within P;
-- −1 if Q outside of P;
-- 0 if Q on an edge of P
function M.point_in_polygon(poly, point)
local t = -1
for i=1, #poly-1 do
t = t * M.cross_prod_test(point.lon, point.lat, poly[i].lon, poly[i].lat, poly[i+1].lon, poly[i+1].lat)
if t == 0 then break end
end
return t
end
-- Convert rectangle defined by two point into polygon
function M.two_point_rec_to_poly(rec)
return {
rec[1],
{ lon = rec[2].lon, lat = rec[1].lat },
rec[2],
{ lon = rec[1].lon, lat = rec[2].lat },
}
end
return M
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