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author | Norbert Preining <norbert@preining.info> | 2023-01-16 03:03:27 +0000 |
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committer | Norbert Preining <norbert@preining.info> | 2023-01-16 03:03:27 +0000 |
commit | 6f9e1680085e7bb4d258f6f8116369d122e196e1 (patch) | |
tree | 9ac0ecb239240d1d672b188f29c1479de215074b /graphics/pgf/base/tex/generic/graphdrawing/lua/pgf/gd/model/Path.lua | |
parent | b8345f39630408bb198e7636381ce4240154ca9b (diff) |
CTAN sync 202301160303
Diffstat (limited to 'graphics/pgf/base/tex/generic/graphdrawing/lua/pgf/gd/model/Path.lua')
-rw-r--r-- | graphics/pgf/base/tex/generic/graphdrawing/lua/pgf/gd/model/Path.lua | 1278 |
1 files changed, 1278 insertions, 0 deletions
diff --git a/graphics/pgf/base/tex/generic/graphdrawing/lua/pgf/gd/model/Path.lua b/graphics/pgf/base/tex/generic/graphdrawing/lua/pgf/gd/model/Path.lua new file mode 100644 index 0000000000..cbd0f079bf --- /dev/null +++ b/graphics/pgf/base/tex/generic/graphdrawing/lua/pgf/gd/model/Path.lua @@ -0,0 +1,1278 @@ +-- Copyright 2014 by Till Tantau +-- +-- This file may be distributed an/or modified +-- +-- 1. under the LaTeX Project Public License and/or +-- 2. under the GNU Public License +-- +-- See the file doc/generic/pgf/licenses/LICENSE for more information + +-- @release $Header$ + + +--- +-- A Path models a path in the plane. +-- +-- Following the PostScript/\textsc{pdf}/\textsc{svg} convention, a +-- path consists of a series of path segments, each of which can be +-- closed or not. Each path segment, in turn, consists of a series of +-- Bézier curves and straight line segments; see +-- Section~\ref{section-paths} for an introduction to paths in +-- general. +-- +-- A |Path| object is a table whose array part stores +-- |Coordinate| objects, |strings|, and |function|s that +-- describe the path of the edge. The following strings are allowed in +-- this array: +-- % +-- \begin{itemize} +-- \item |"moveto"| The line's path should stop at the current +-- position and then start anew at the next coordinate in the array. +-- \item |"lineto"| The line should continue from the current position +-- to the next coordinate in the array. +-- \item |"curveto"| The line should continue form the current +-- position with a Bézier curve that is specified by the next three +-- |Coordinate| objects (in the usual manner). +-- \item |"closepath"| The line's path should be ``closed'' in the sense +-- that the current subpath that was started with the most recent +-- moveto operation should now form a closed curve. +-- \end{itemize} +-- +-- Instead of a |Coordinate|, a |Path| may also contain a function. In +-- this case, the function, when called, must return the |Coordinate| +-- that is ``meant'' by the position. This allows algorithms to +-- add coordinates to a path that are still not fixed at the moment +-- they are added to the path. + +local Path = {} +Path.__index = Path + + +-- Namespace + +require("pgf.gd.model").Path = Path + + +-- Imports + +local Coordinate = require "pgf.gd.model.Coordinate" +local Bezier = require "pgf.gd.lib.Bezier" + +local lib = require "pgf.gd.lib" + + +-- Private function + +function Path.rigid (x) + if type(x) == "function" then + return x() + else + return x + end +end + +local rigid = Path.rigid + + +--- +-- Creates an empty path. +-- +-- @param initial A table containing an array of strings and +-- coordinates that constitute the path. Coordinates may be given as +-- tables or as a pair of numbers. In this case, each pair of numbers +-- is converted into one coordinate. If omitted, a new empty path +-- is created. +-- +-- @return A empty Path +-- +function Path.new(initial) + if initial then + local new = {} + local i = 1 + local count = 0 + while i <= #initial do + local e = initial[i] + if type(e) == "string" then + assert (count == 0, "illformed path") + if e == "moveto" then + count = 1 + elseif e == "lineto" then + count = 1 + elseif e == "closepath" then + count = 0 + elseif e == "curveto" then + count = 3 + else + error ("unknown path command " .. e) + end + new[#new+1] = e + elseif type(e) == "number" then + if count == 0 then + new[#new+1] = "lineto" + else + count = count - 1 + end + new[#new+1] = Coordinate.new(e,initial[i+1]) + i = i + 1 + elseif type(e) == "table" or type(e) == "function" then + if count == 0 then + new[#new+1] = "lineto" + else + count = count - 1 + end + new[#new+1] = e + else + error ("invalid object on path") + end + i = i + 1 + end + return setmetatable(new, Path) + else + return setmetatable({}, Path) + end +end + + +--- +-- Creates a copy of a path. +-- +-- @return A copy of the path + +function Path:clone() + local new = {} + for _,x in ipairs(self) do + if type(x) == "table" then + new[#new+1] = x:clone() + else + new[#new+1] = x + end + end + return setmetatable(new, Path) +end + + + +--- +-- Returns the path in reverse order. +-- +-- @return A copy of the reversed path + +function Path:reversed() + + -- First, build segments + local subpaths = {} + local subpath = {} + + local function closepath () + if subpath.start then + subpaths [#subpaths + 1] = subpath + subpath = {} + end + end + + local prev + local start + + local i = 1 + while i <= #self do + local x = self[i] + if x == "lineto" then + subpath[#subpath+1] = { + action = 'lineto', + from = prev, + to = self[i+1] + } + prev = self[i+1] + i = i + 2 + elseif x == "moveto" then + closepath() + prev = self[i+1] + start = prev + subpath.start = prev + i = i + 2 + elseif x == "closepath" then + subpath [#subpath + 1] = { + action = "closepath", + from = prev, + to = start, + } + prev = nil + start = nil + closepath() + i = i + 1 + elseif x == "curveto" then + local s1, s2, to = self[i+1], self[i+2], self[i+3] + subpath [#subpath + 1] = { + action = "curveto", + from = prev, + to = to, + support_1 = s1, + support_2 = s2, + } + prev = self[i+3] + i = i + 4 + else + error ("illegal path command '" .. x .. "'") + end + end + closepath () + + local new = Path.new () + + for _,subpath in ipairs(subpaths) do + if #subpath == 0 then + -- A subpath that consists only of a moveto: + new:appendMoveto(subpath.start) + else + -- We start with a moveto to the end point: + new:appendMoveto(subpath[#subpath].to) + + -- Now walk backwards: + for i=#subpath,1,-1 do + if subpath[i].action == "lineto" then + new:appendLineto(subpath[i].from) + elseif subpath[i].action == "closepath" then + new:appendLineto(subpath[i].from) + elseif subpath[i].action == "curveto" then + new:appendCurveto(subpath[i].support_2, + subpath[i].support_1, + subpath[i].from) + else + error("illegal path command") + end + end + + -- Append a closepath, if necessary + if subpath[#subpath].action == "closepath" then + new:appendClosepath() + end + end + end + + return new +end + + +--- +-- Transform all points on a path. +-- +-- @param t A transformation, see |pgf.gd.lib.Transform|. It is +-- applied to all |Coordinate| objects on the path. + +function Path:transform(t) + for _,c in ipairs(self) do + if type(c) == "table" then + c:apply(t) + end + end +end + + +--- +-- Shift all points on a path. +-- +-- @param x An $x$-shift +-- @param y A $y$-shift + +function Path:shift(x,y) + for _,c in ipairs(self) do + if type(c) == "table" then + c.x = c.x + x + c.y = c.y + y + end + end +end + + +--- +-- Shift by all points on a path. +-- +-- @param x A coordinate + +function Path:shiftByCoordinate(x) + for _,c in ipairs(self) do + if type(c) == "table" then + c.x = c.x + x.x + c.y = c.y + x.y + end + end +end + + +--- +-- Makes the path empty. +-- + +function Path:clear() + for i=1,#self do + self[i] = nil + end +end + + +--- +-- Appends a |moveto| to the path. +-- +-- @param x A |Coordinate| or |function| or, if the |y| parameter is +-- not |nil|, a number that is the $x$-part of a coordinate. +-- @param y The $y$-part of the coordinate. + +function Path:appendMoveto(x,y) + self[#self + 1] = "moveto" + self[#self + 1] = y and Coordinate.new(x,y) or x +end + + +--- +-- Appends a |lineto| to the path. +-- +-- @param x A |Coordinate| or |function|, if the |y| parameter is not +-- |nil|, a number that is the $x$-part of a coordinate. +-- @param y The $y$-part of the coordinate. + +function Path:appendLineto(x,y) + self[#self + 1] = "lineto" + self[#self + 1] = y and Coordinate.new(x,y) or x +end + + + +--- +-- Appends a |closepath| to the path. + +function Path:appendClosepath() + self[#self + 1] = "closepath" +end + + +--- +-- Appends a |curveto| to the path. There can be either three +-- coordinates (or functions) as parameters (the two support points +-- and the target) or six numbers, where two consecutive numbers form a +-- |Coordinate|. Which case is meant is detected by the presence of a +-- sixth non-nil parameter. + +function Path:appendCurveto(a,b,c,d,e,f) + self[#self + 1] = "curveto" + if f then + self[#self + 1] = Coordinate.new(a,b) + self[#self + 1] = Coordinate.new(c,d) + self[#self + 1] = Coordinate.new(e,f) + else + self[#self + 1] = a + self[#self + 1] = b + self[#self + 1] = c + end +end + + + + + + +--- +-- Makes a path ``rigid'', meaning that all coordinates that are only +-- given as functions are replaced by the values these functions +-- yield. + +function Path:makeRigid() + for i=1,#self do + self[i] = rigid(self[i]) + end +end + + +--- +-- Returns an array of all coordinates that are present in a +-- path. This means, essentially, that all strings are filtered out. +-- +-- @return An array of all coordinate objects on the path. + +function Path:coordinates() + local cloud = {} + for i=1,#self do + local p = self[i] + if type(p) == "table" then + cloud[#cloud + 1] = p + elseif type(p) == "function" then + cloud[#cloud + 1] = p() + end + end + return cloud +end + + +--- +-- Returns a bounding box of the path. This will not necessarily be +-- the minimal bounding box in case the path contains curves because, +-- then, the support points of the curve are used for the computation +-- rather than the actual bounding box of the path. +-- +-- If the path contains no coordinates, all return values are 0. +-- +-- @return |min_x| The minimum $x$ value of the bounding box of the path +-- @return |min_y| The minimum $y$ value +-- @return |max_x| +-- @return |max_y| +-- @return |center_x| The center of the bounding box +-- @return |center_y| + +function Path:boundingBox() + if #self > 0 then + local min_x, min_y = math.huge, math.huge + local max_x, max_y = -math.huge, -math.huge + + for i=1,#self do + local c = rigid(self[i]) + if type(c) == "table" then + local x = c.x + local y = c.y + if x < min_x then min_x = x end + if y < min_y then min_y = y end + if x > max_x then max_x = x end + if y > max_y then max_y = y end + end + end + + if min_x ~= math.huge then + return min_x, min_y, max_x, max_y, (min_x+max_x) / 2, (min_y+max_y) / 2 + end + end + return 0, 0, 0, 0, 0, 0 +end + + +-- Forwards + +local segmentize, bb, boxes_intersect, intersect_curves + +local eps = 0.0001 + + + +--- +-- Computes all intersections of a path with another path and returns +-- them as an array of coordinates. The intersections will be sorted +-- ``along the path |self|''. The implementation uses a +-- divide-and-conquer approach that should be reasonably fast in +-- practice. +-- +-- @param path Another path +-- +-- @return Array of all intersections of |path| with |self| in the +-- order they appear on |self|. Each entry of this array is a table +-- with the following fields: +-- % +-- \begin{itemize} +-- \item |index| The index of the segment in |self| where +-- the intersection occurs. +-- \item |time| The ``time'' at which a point traveling along the +-- segment from its start point to its end point. +-- \item |point| The point itself. +-- \end{itemize} + +function Path:intersectionsWith(path) + + local p1 = segmentize(self) + local memo1 = prepare_memo(p1) + local p2 = segmentize(path) + local memo2 = prepare_memo(p2) + + local intersections = {} + + local function intersect_segments(i1, i2) + + local s1 = p1[i1] + local s2 = p2[i2] + local r = {} + + if s1.action == 'lineto' and s2.action == 'lineto' then + local a = s2.to.x - s2.from.x + local b = s1.from.x - s1.to.x + local c = s2.from.x - s1.from.x + local d = s2.to.y - s2.from.y + local e = s1.from.y - s1.to.y + local f = s2.from.y - s1.from.y + + local det = a*e - b*d + + if math.abs(det) > eps*eps then + local t, s = (c*d - a*f)/det, (b*f - e*c)/det + + if t >= 0 and t<=1 and s>=0 and s <= 1 then + local p = s1.from:clone() + p:moveTowards(s1.to, t) + return { { time = t, point = p } } + end + end + elseif s1.action == 'lineto' and s2.action == 'curveto' then + intersect_curves (0, 1, + s1.from.x, s1.from.y, + s1.from.x*2/3+s1.to.x*1/3, s1.from.y*2/3+s1.to.y*1/3, + s1.from.x*1/3+s1.to.x*2/3, s1.from.y*1/3+s1.to.y*2/3, + s1.to.x, s1.to.y, + s2.from.x, s2.from.y, + s2.support_1.x, s2.support_1.y, + s2.support_2.x, s2.support_2.y, + s2.to.x, s2.to.y, + r) + elseif s1.action == 'curveto' and s2.action == 'lineto' then + intersect_curves (0, 1, + s1.from.x, s1.from.y, + s1.support_1.x, s1.support_1.y, + s1.support_2.x, s1.support_2.y, + s1.to.x, s1.to.y, + s2.from.x, s2.from.y, + s2.from.x*2/3+s2.to.x*1/3, s2.from.y*2/3+s2.to.y*1/3, + s2.from.x*1/3+s2.to.x*2/3, s2.from.y*1/3+s2.to.y*2/3, + s2.to.x, s2.to.y, + r) + else + intersect_curves (0, 1, + s1.from.x, s1.from.y, + s1.support_1.x, s1.support_1.y, + s1.support_2.x, s1.support_2.y, + s1.to.x, s1.to.y, + s2.from.x, s2.from.y, + s2.support_1.x, s2.support_1.y, + s2.support_2.x, s2.support_2.y, + s2.to.x, s2.to.y, + r) + end + return r + end + + local function intersect (i1, j1, i2, j2) + + if i1 > j1 or i2 > j2 then + return + end + + local bb1 = bb(i1, j1, memo1) + local bb2 = bb(i2, j2, memo2) + + if boxes_intersect(bb1, bb2) then + -- Ok, need to do something + if i1 == j1 and i2 == j2 then + local intersects = intersect_segments (i1, i2) + for _,t in ipairs(intersects) do + intersections[#intersections+1] = { + time = t.time, + index = p1[i1].path_pos, + point = t.point + } + end + elseif i1 == j1 then + local m2 = math.floor((i2 + j2) / 2) + intersect(i1, j1, i2, m2) + intersect(i1, j1, m2+1, j2) + elseif i2 == j2 then + local m1 = math.floor((i1 + j1) / 2) + intersect(i1, m1, i2, j2) + intersect(m1+1, j1, i2, j2) + else + local m1 = math.floor((i1 + j1) / 2) + local m2 = math.floor((i2 + j2) / 2) + intersect(i1, m1, i2, m2) + intersect(m1+1, j1, i2, m2) + intersect(i1, m1, m2+1, j2) + intersect(m1+1, j1, m2+1, j2) + end + end + end + + -- Run the recursion + intersect(1, #p1, 1, #p2) + + -- Sort + table.sort(intersections, function(a,b) + return a.index < b.index or + a.index == b.index and a.time < b.time + end) + + -- Remove duplicates + local remains = {} + remains[1] = intersections[1] + for i=2,#intersections do + local next = intersections[i] + local prev = remains[#remains] + if math.abs(next.point.x - prev.point.x) + math.abs(next.point.y - prev.point.y) > eps then + remains[#remains+1] = next + end + end + + return remains +end + + +-- Returns true if two bounding boxes intersection + +function boxes_intersect (bb1, bb2) + return (bb1.max_x >= bb2.min_x - eps*eps and + bb1.min_x <= bb2.max_x + eps*eps and + bb1.max_y >= bb2.min_y - eps*eps and + bb1.min_y <= bb2.max_y + eps*eps) +end + + +-- Turns a path into a sequence of segments, each being either a +-- lineto or a curveto from some point to another point. It also sets +-- up a memorization array for the bounding boxes. + +function segmentize (path) + + local prev + local start + local s = {} + + local i = 1 + while i <= #path do + local x = path[i] + + if x == "lineto" then + x = rigid(path[i+1]) + s [#s + 1] = { + path_pos = i, + action = "lineto", + from = prev, + to = x, + bb = { + min_x = math.min(prev.x, x.x), + max_x = math.max(prev.x, x.x), + min_y = math.min(prev.y, x.y), + max_y = math.max(prev.y, x.y), + } + } + prev = x + i = i + 2 + elseif x == "moveto" then + prev = rigid(path[i+1]) + start = prev + i = i + 2 + elseif x == "closepath" then + s [#s + 1] = { + path_pos = i, + action = "lineto", + from = prev, + to = start, + bb = { + min_x = math.min(prev.x, start.x), + max_x = math.max(prev.x, start.x), + min_y = math.min(prev.y, start.y), + max_y = math.max(prev.y, start.y), + } + } + prev = nil + start = nil + i = i + 1 + elseif x == "curveto" then + local s1, s2, to = rigid(path[i+1]), rigid(path[i+2]), rigid(path[i+3]) + s [#s + 1] = { + action = "curveto", + path_pos = i, + from = prev, + to = to, + support_1 = s1, + support_2 = s2, + bb = { + min_x = math.min(prev.x, s1.x, s2.x, to.x), + max_x = math.max(prev.x, s1.x, s2.x, to.x), + min_y = math.min(prev.y, s1.y, s2.y, to.y), + max_y = math.max(prev.y, s1.y, s2.y, to.y), + } + } + prev = path[i+3] + i = i + 4 + else + error ("illegal path command '" .. x .. "'") + end + end + + return s +end + + +function prepare_memo (s) + + local memo = {} + + memo.base = #s + + -- Fill memo table + for i,e in ipairs (s) do + memo[i*#s + i] = e.bb + end + + return memo +end + + +-- This function computes the bounding box of all segments between i +-- and j (inclusively) + +function bb (i, j, memo) + local b = memo[memo.base*i + j] + if not b then + assert (i < j, "memorization table filled incorrectly") + + local mid = math.floor((i+j)/2) + local bb1 = bb (i, mid, memo) + local bb2 = bb (mid+1, j, memo) + b = { + min_x = math.min(bb1.min_x, bb2.min_x), + max_x = math.max(bb1.max_x, bb2.max_x), + min_y = math.min(bb1.min_y, bb2.min_y), + max_y = math.max(bb1.max_y, bb2.max_y) + } + memo[memo.base*i + j] = b + end + + return b +end + + + +-- Intersect two Bézier curves. + +function intersect_curves(t0, t1, + c1_ax, c1_ay, c1_bx, c1_by, + c1_cx, c1_cy, c1_dx, c1_dy, + c2_ax, c2_ay, c2_bx, c2_by, + c2_cx, c2_cy, c2_dx, c2_dy, + intersections) + + -- Only do something, if the bounding boxes intersect: + local c1_min_x = math.min(c1_ax, c1_bx, c1_cx, c1_dx) + local c1_max_x = math.max(c1_ax, c1_bx, c1_cx, c1_dx) + local c1_min_y = math.min(c1_ay, c1_by, c1_cy, c1_dy) + local c1_max_y = math.max(c1_ay, c1_by, c1_cy, c1_dy) + local c2_min_x = math.min(c2_ax, c2_bx, c2_cx, c2_dx) + local c2_max_x = math.max(c2_ax, c2_bx, c2_cx, c2_dx) + local c2_min_y = math.min(c2_ay, c2_by, c2_cy, c2_dy) + local c2_max_y = math.max(c2_ay, c2_by, c2_cy, c2_dy) + + if c1_max_x >= c2_min_x and + c1_min_x <= c2_max_x and + c1_max_y >= c2_min_y and + c1_min_y <= c2_max_y then + + -- Everything "near together"? + if c1_max_x - c1_min_x < eps and c1_max_y - c1_min_y < eps then + + -- Compute intersection of lines c1_a to c1_d and c2_a to c2_d + local a = c2_dx - c2_ax + local b = c1_ax - c1_dx + local c = c2_ax - c1_ax + local d = c2_dy - c2_ay + local e = c1_ay - c1_dy + local f = c2_ay - c1_ay + + local det = a*e - b*d + local t + + t = (c*d - a*f)/det + if t<0 then + t=0 + elseif t>1 then + t=1 + end + + intersections [#intersections + 1] = { + time = t0 + t*(t1-t0), + point = Coordinate.new(c1_ax + t*(c1_dx-c1_ax), c1_ay+t*(c1_dy-c1_ay)) + } + else + -- Cut 'em in half! + local c1_ex, c1_ey = (c1_ax + c1_bx)/2, (c1_ay + c1_by)/2 + local c1_fx, c1_fy = (c1_bx + c1_cx)/2, (c1_by + c1_cy)/2 + local c1_gx, c1_gy = (c1_cx + c1_dx)/2, (c1_cy + c1_dy)/2 + + local c1_hx, c1_hy = (c1_ex + c1_fx)/2, (c1_ey + c1_fy)/2 + local c1_ix, c1_iy = (c1_fx + c1_gx)/2, (c1_fy + c1_gy)/2 + + local c1_jx, c1_jy = (c1_hx + c1_ix)/2, (c1_hy + c1_iy)/2 + + local c2_ex, c2_ey = (c2_ax + c2_bx)/2, (c2_ay + c2_by)/2 + local c2_fx, c2_fy = (c2_bx + c2_cx)/2, (c2_by + c2_cy)/2 + local c2_gx, c2_gy = (c2_cx + c2_dx)/2, (c2_cy + c2_dy)/2 + + local c2_hx, c2_hy = (c2_ex + c2_fx)/2, (c2_ey + c2_fy)/2 + local c2_ix, c2_iy = (c2_fx + c2_gx)/2, (c2_fy + c2_gy)/2 + + local c2_jx, c2_jy = (c2_hx + c2_ix)/2, (c2_hy + c2_iy)/2 + + intersect_curves (t0, (t0+t1)/2, + c1_ax, c1_ay, c1_ex, c1_ey, c1_hx, c1_hy, c1_jx, c1_jy, + c2_ax, c2_ay, c2_ex, c2_ey, c2_hx, c2_hy, c2_jx, c2_jy, + intersections) + intersect_curves (t0, (t0+t1)/2, + c1_ax, c1_ay, c1_ex, c1_ey, c1_hx, c1_hy, c1_jx, c1_jy, + c2_jx, c2_jy, c2_ix, c2_iy, c2_gx, c2_gy, c2_dx, c2_dy, + intersections) + intersect_curves ((t0+t1)/2, t1, + c1_jx, c1_jy, c1_ix, c1_iy, c1_gx, c1_gy, c1_dx, c1_dy, + c2_ax, c2_ay, c2_ex, c2_ey, c2_hx, c2_hy, c2_jx, c2_jy, + intersections) + intersect_curves ((t0+t1)/2, t1, + c1_jx, c1_jy, c1_ix, c1_iy, c1_gx, c1_gy, c1_dx, c1_dy, + c2_jx, c2_jy, c2_ix, c2_iy, c2_gx, c2_gy, c2_dx, c2_dy, + intersections) + end + end +end + + +--- +-- Shorten a path at the beginning. We are given the index of a +-- segment inside the path as well as a point in time along this +-- segment. The path is now shortened so that everything before this +-- segment and everything in the segment before the given time is +-- removed from the path. +-- +-- @param index The index of a path segment. +-- @param time A time along the specified path segment. + +function Path:cutAtBeginning(index, time) + + local cut_path = Path:new () + + -- Ok, first, we need to find the segment *before* the current + -- one. Usually, this will be a moveto or a lineto, but things could + -- be different. + assert (type(self[index-1]) == "table" or type(self[index-1]) == "function", + "segment before intersection does not end with a coordinate") + + local from = rigid(self[index-1]) + local action = self[index] + + -- Now, depending on the type of segment, we do different things: + if action == "lineto" then + + -- Ok, compute point: + local to = rigid(self[index+1]) + + from:moveTowards(to, time) + + -- Ok, this is easy: We start with a fresh moveto ... + cut_path[1] = "moveto" + cut_path[2] = from + + -- ... and copy the rest + for i=index,#self do + cut_path[#cut_path+1] = self[i] + end + elseif action == "curveto" then + + local to = rigid(self[index+3]) + local s1 = rigid(self[index+1]) + local s2 = rigid(self[index+2]) + + -- Now, compute the support vectors and the point at time: + from:moveTowards(s1, time) + s1:moveTowards(s2, time) + s2:moveTowards(to, time) + + from:moveTowards(s1, time) + s1:moveTowards(s2, time) + + from:moveTowards(s1, time) + + -- Ok, this is easy: We start with a fresh moveto ... + cut_path[1] = "moveto" + cut_path[2] = from + cut_path[3] = "curveto" + cut_path[4] = s1 + cut_path[5] = s2 + cut_path[6] = to + + -- ... and copy the rest + for i=index+4,#self do + cut_path[#cut_path+1] = self[i] + end + + elseif action == "closepath" then + -- Let us find the start point: + local found + for i=index,1,-1 do + if self[i] == "moveto" then + -- Bingo: + found = i + break + end + end + + assert(found, "no moveto found in path") + + local to = rigid(self[found+1]) + from:moveTowards(to,time) + + cut_path[1] = "moveto" + cut_path[2] = from + cut_path[3] = "lineto" + cut_path[4] = to + + -- ... and copy the rest + for i=index+1,#self do + cut_path[#cut_path+1] = self[i] + end + else + error ("wrong path operation") + end + + -- Move cut_path back: + for i=1,#cut_path do + self[i] = cut_path[i] + end + for i=#cut_path+1,#self do + self[i] = nil + end +end + + + + +--- +-- Shorten a path at the end. This method works like |cutAtBeginning|, +-- only the path is cut at the end. +-- +-- @param index The index of a path segment. +-- @param time A time along the specified path segment. + +function Path:cutAtEnd(index, time) + + local cut_path = Path:new () + + -- Ok, first, we need to find the segment *before* the current + -- one. Usually, this will be a moveto or a lineto, but things could + -- be different. + assert (type(self[index-1]) == "table" or type(self[index-1]) == "function", + "segment before intersection does not end with a coordinate") + + local from = rigid(self[index-1]) + local action = self[index] + + -- Now, depending on the type of segment, we do different things: + if action == "lineto" then + + -- Ok, compute point: + local to = rigid(self[index+1]) + to:moveTowards(from, 1-time) + + for i=1,index do + cut_path[i] = self[i] + end + cut_path[index+1] = to + + elseif action == "curveto" then + + local s1 = rigid(self[index+1]) + local s2 = rigid(self[index+2]) + local to = rigid(self[index+3]) + + -- Now, compute the support vectors and the point at time: + to:moveTowards(s2, 1-time) + s2:moveTowards(s1, 1-time) + s1:moveTowards(from, 1-time) + + to:moveTowards(s2, 1-time) + s2:moveTowards(s1, 1-time) + + to:moveTowards(s2, 1-time) + + -- ... and copy the rest + for i=1,index do + cut_path[i] = self[i] + end + + cut_path[index+1] = s1 + cut_path[index+2] = s2 + cut_path[index+3] = to + + elseif action == "closepath" then + -- Let us find the start point: + local found + for i=index,1,-1 do + if self[i] == "moveto" then + -- Bingo: + found = i + break + end + end + + assert(found, "no moveto found in path") + + local to = rigid(self[found+1]:clone()) + to:moveTowards(from,1-time) + + for i=1,index-1 do + cut_path[i] = self[i] + end + cut_path[index] = 'lineto' + cut_path[index+1] = to + else + error ("wrong path operation") + end + + -- Move cut_path back: + for i=1,#cut_path do + self[i] = cut_path[i] + end + for i=#cut_path+1,#self do + self[i] = nil + end +end + + + + +--- +-- ``Pads'' the path. The idea is the following: Suppose we stroke the +-- path with a pen whose width is twice the value |padding|. The outer +-- edge of this stroked drawing is now a path by itself. The path will +-- be a bit longer and ``larger''. The present function tries to +-- compute an approximation to this resulting path. +-- +-- The algorithm used to compute the enlarged part does not necessarily +-- compute the precise new path. It should work correctly for polyline +-- paths, but not for curved paths. +-- +-- @param padding A padding distance. +-- @return The padded path. +-- + +function Path:pad(padding) + + local padded = self:clone() + padded:makeRigid() + + if padding == 0 then + return padded + end + + -- First, decompose the path into subpaths: + local subpaths = {} + local subpath = {} + local start_index = 1 + + local function closepath(end_index) + if #subpath >= 1 then + subpath.start_index = start_index + subpath.end_index = end_index + start_index = end_index + 1 + + local start = 1 + if (subpath[#subpath] - subpath[1]):norm() < 0.01 and subpath[2] then + start = 2 + subpath.skipped = subpath[1] + end + subpath[#subpath + 1] = subpath[start] + subpath[#subpath + 1] = subpath[start+1] + subpaths[#subpaths + 1] = subpath + subpath = {} + end + end + + for i,p in ipairs(padded) do + if p ~= "closepath" then + if type(p) == "table" then + subpath[#subpath + 1] = p + end + else + closepath (i) + end + end + closepath(#padded) + + -- Second, iterate over the subpaths: + for _,subpath in ipairs(subpaths) do + local new_coordinates = {} + local _,_,_,_,c_x,c_y = Coordinate.boundingBox(subpath) + local c = Coordinate.new(c_x,c_y) + + -- Find out the orientation of the path + local count = 0 + for i=1,#subpath-2 do + local d2 = subpath[i+1] - subpath[i] + local d1 = subpath[i+2] - subpath[i+1] + + local diff = math.atan2(d2.y,d2.x) - math.atan2(d1.y,d1.x) + + if diff < -math.pi then + count = count + 1 + elseif diff > math.pi then + count = count - 1 + end + end + + for i=2,#subpath-1 do + local p = subpath[i] + local d1 = subpath[i] - subpath[i-1] + local d2 = subpath[i+1] - subpath[i] + + local orth1 = Coordinate.new(-d1.y, d1.x) + local orth2 = Coordinate.new(-d2.y, d2.x) + + orth1:normalize() + orth2:normalize() + + if count < 0 then + orth1:scale(-1) + orth2:scale(-1) + end + + -- Ok, now we want to compute the intersection of the lines + -- perpendicular to p + padding*orth1 and p + padding*orth2: + + local det = orth1.x * orth2.y - orth1.y * orth2.x + + local c + if math.abs(det) < 0.1 then + c = orth1 + orth2 + c:scale(padding/2) + else + c = Coordinate.new (padding*(orth2.y-orth1.y)/det, padding*(orth1.x-orth2.x)/det) + end + + new_coordinates[i] = c+p + end + + for i=2,#subpath-1 do + local p = subpath[i] + local new_p = new_coordinates[i] + p.x = new_p.x + p.y = new_p.y + end + + if subpath.skipped then + local p = subpath[1] + local new_p = new_coordinates[#subpath-2] + p.x = new_p.x + p.y = new_p.y + end + + -- Now, we need to correct the curveto fields: + for i=subpath.start_index,subpath.end_index do + if self[i] == 'curveto' then + local from = rigid(self[i-1]) + local s1 = rigid(self[i+1]) + local s2 = rigid(self[i+2]) + local to = rigid(self[i+3]) + + local p1x, p1y, _, _, h1x, h1y = + Bezier.atTime(from.x, from.y, s1.x, s1.y, s2.x, s2.y, + to.x, to.y, 1/3) + + local p2x, p2y, _, _, _, _, h2x, h2y = + Bezier.atTime(from.x, from.y, s1.x, s1.y, s2.x, s2.y, + to.x, to.y, 2/3) + + local orth1 = Coordinate.new (p1y - h1y, -(p1x - h1x)) + orth1:normalize() + orth1:scale(-padding) + + local orth2 = Coordinate.new (p2y - h2y, -(p2x - h2x)) + orth2:normalize() + orth2:scale(padding) + + if count < 0 then + orth1:scale(-1) + orth2:scale(-1) + end + + local new_s1, new_s2 = + Bezier.supportsForPointsAtTime(padded[i-1], + Coordinate.new(p1x+orth1.x,p1y+orth1.y), 1/3, + Coordinate.new(p2x+orth2.x,p2y+orth2.y), 2/3, + padded[i+3]) + + padded[i+1] = new_s1 + padded[i+2] = new_s2 + end + end + end + + return padded +end + + + +--- +-- Appends an arc (as in the sense of ``a part of the circumference of +-- a circle'') to the path. You may optionally provide a +-- transformation matrix, which will be applied to the arc. In detail, +-- the following happens: We first invert the transformation +-- and apply it to the start point. Then we compute the arc +-- ``normally'', as if no transformation matrix were present. Then we +-- apply the transformation matrix to all computed points. +-- +-- @function Path:appendArc(start_angle,end_angle,radius,trans) +-- +-- @param start_angle The start angle of the arc. Must be specified in +-- degrees. +-- @param end_angle the end angle of the arc. +-- @param radius The radius of the circle on which this arc lies. +-- @param trans A transformation matrix. If |nil|, the identity +-- matrix will be assumed. + +Path.appendArc = lib.ondemand("Path_arced", Path, "appendArc") + + + +--- +-- Appends a clockwise arc (as in the sense of ``a part of the circumference of +-- a circle'') to the path such that it ends at a given point. If a +-- transformation matrix is given, both start and end point are first +-- transformed according to the inverted transformation, then the arc +-- is computed and then transformed back. +-- +-- @function Path:appendArcTo(target,radius_or_center,clockwise,trans) +-- +-- @param target The point where the arc should end. +-- @param radius_or_center If a number, it is the radius of the circle +-- on which this arc lies. If it is a |Coordinate|, this is the center +-- of the circle. +-- @param clockwise If true, the arc will be clockwise. Otherwise (the +-- default, if nothing or |nil| is given), the arc will be counter +-- clockwise. +-- @param trans A transformation matrix. If missing, +-- the identity matrix is assumed. + +Path.appendArcTo = lib.ondemand("Path_arced", Path, "appendArcTo") + + + + +-- +-- @return The Path as string. +-- +function Path:__tostring() + local r = {} + local i = 1 + while i <= #self do + local p = self[i] + + if p == "lineto" then + r [#r+1] = " -- " .. tostring(rigid(self[i+1])) + i = i + 1 + elseif p == "moveto" then + r [#r+1] = " " .. tostring(rigid(self[i+1]) ) + i = i + 1 + elseif p == "curveto" then + r [#r+1] = " .. controls " .. tostring(rigid(self[i+1])) .. " and " .. + tostring(rigid(self[i+2])) .. " .. " .. tostring(rigid(self[i+3])) + i = i + 3 + elseif p == "closepath" then + r [#r+1] = " -- cycle" + else + error("illegal path command") + end + i = i + 1 + end + return table.concat(r) +end + + + +-- Done + +return Path |