2 * Copyright 2011 Google Inc.
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
8 #ifndef GrPathUtils_DEFINED
9 #define GrPathUtils_DEFINED
19 * Utilities for evaluating paths.
21 namespace GrPathUtils {
22 SkScalar scaleToleranceToSrc(SkScalar devTol,
23 const SkMatrix& viewM,
24 const SkRect& pathBounds);
26 /// Since we divide by tol if we're computing exact worst-case bounds,
27 /// very small tolerances will be increased to gMinCurveTol.
28 int worstCasePointCount(const SkPath&,
32 /// Since we divide by tol if we're computing exact worst-case bounds,
33 /// very small tolerances will be increased to gMinCurveTol.
34 uint32_t quadraticPointCount(const SkPoint points[], SkScalar tol);
36 uint32_t generateQuadraticPoints(const SkPoint& p0,
43 /// Since we divide by tol if we're computing exact worst-case bounds,
44 /// very small tolerances will be increased to gMinCurveTol.
45 uint32_t cubicPointCount(const SkPoint points[], SkScalar tol);
47 uint32_t generateCubicPoints(const SkPoint& p0,
55 // A 2x3 matrix that goes from the 2d space coordinates to UV space where
56 // u^2-v = 0 specifies the quad. The matrix is determined by the control
57 // points of the quadratic.
61 // Initialize the matrix from the control pts
62 QuadUVMatrix(const SkPoint controlPts[3]) { this->set(controlPts); }
63 void set(const SkPoint controlPts[3]);
66 * Applies the matrix to vertex positions to compute UV coords. This
67 * has been templated so that the compiler can easliy unroll the loop
68 * and reorder to avoid stalling for loads. The assumption is that a
69 * path renderer will have a small fixed number of vertices that it
70 * uploads for each quad.
72 * N is the number of vertices.
73 * STRIDE is the size of each vertex.
74 * UV_OFFSET is the offset of the UV values within each vertex.
75 * vertices is a pointer to the first vertex.
77 template <int N, size_t STRIDE, size_t UV_OFFSET>
78 void apply(const void* vertices) {
79 intptr_t xyPtr = reinterpret_cast<intptr_t>(vertices);
80 intptr_t uvPtr = reinterpret_cast<intptr_t>(vertices) + UV_OFFSET;
87 for (int i = 0; i < N; ++i) {
88 const SkPoint* xy = reinterpret_cast<const SkPoint*>(xyPtr);
89 SkPoint* uv = reinterpret_cast<SkPoint*>(uvPtr);
90 uv->fX = sx * xy->fX + kx * xy->fY + tx;
91 uv->fY = ky * xy->fX + sy * xy->fY + ty;
100 // Input is 3 control points and a weight for a bezier conic. Calculates the
101 // three linear functionals (K,L,M) that represent the implicit equation of the
105 // K = (klm[0], klm[1], klm[2])
106 // L = (klm[3], klm[4], klm[5])
107 // M = (klm[6], klm[7], klm[8])
108 void getConicKLM(const SkPoint p[3], const SkScalar weight, SkScalar klm[9]);
110 // Converts a cubic into a sequence of quads. If working in device space
111 // use tolScale = 1, otherwise set based on stretchiness of the matrix. The
112 // result is sets of 3 points in quads (TODO: share endpoints in returned
114 // When we approximate a cubic {a,b,c,d} with a quadratic we may have to
115 // ensure that the new control point lies between the lines ab and cd. The
116 // convex path renderer requires this. It starts with a path where all the
117 // control points taken together form a convex polygon. It relies on this
118 // property and the quadratic approximation of cubics step cannot alter it.
119 // Setting constrainWithinTangents to true enforces this property. When this
120 // is true the cubic must be simple and dir must specify the orientation of
121 // the cubic. Otherwise, dir is ignored.
122 void convertCubicToQuads(const SkPoint p[4],
124 bool constrainWithinTangents,
125 SkPath::Direction dir,
126 SkTArray<SkPoint, true>* quads);
128 // Chops the cubic bezier passed in by src, at the double point (intersection point)
129 // if the curve is a cubic loop. If it is a loop, there will be two parametric values for
130 // the double point: ls and ms. We chop the cubic at these values if they are between 0 and 1.
132 // Value of 3: ls and ms are both between (0,1), and dst will contain the three cubics,
133 // dst[0..3], dst[3..6], and dst[6..9] if dst is not NULL
134 // Value of 2: Only one of ls and ms are between (0,1), and dst will contain the two cubics,
135 // dst[0..3] and dst[3..6] if dst is not NULL
136 // Value of 1: Neither ls or ms are between (0,1), and dst will contain the one original cubic,
137 // dst[0..3] if dst is not NULL
139 // Optional KLM Calculation:
140 // The function can also return the KLM linear functionals for the chopped cubic implicit form
142 // It will calculate a single set of KLM values that can be shared by all sub cubics, except
143 // for the subsection that is "the loop" the K and L values need to be negated.
145 // klm: Holds the values for the linear functionals as:
146 // K = (klm[0], klm[1], klm[2])
147 // L = (klm[3], klm[4], klm[5])
148 // M = (klm[6], klm[7], klm[8])
149 // klm_rev: These values are flags for the corresponding sub cubic saying whether or not
150 // the K and L values need to be flipped. A value of -1.f means flip K and L and
151 // a value of 1.f means do nothing.
152 // *****DO NOT FLIP M, JUST K AND L*****
154 // Notice that the klm lines are calculated in the same space as the input control points.
155 // If you transform the points the lines will also need to be transformed. This can be done
156 // by mapping the lines with the inverse-transpose of the matrix used to map the points.
157 int chopCubicAtLoopIntersection(const SkPoint src[4], SkPoint dst[10] = NULL,
158 SkScalar klm[9] = NULL, SkScalar klm_rev[3] = NULL);
160 // Input is p which holds the 4 control points of a non-rational cubic Bezier curve.
161 // Output is the coefficients of the three linear functionals K, L, & M which
162 // represent the implicit form of the cubic as f(x,y,w) = K^3 - LM. The w term
163 // will always be 1. The output is stored in the array klm, where the values are:
164 // K = (klm[0], klm[1], klm[2])
165 // L = (klm[3], klm[4], klm[5])
166 // M = (klm[6], klm[7], klm[8])
168 // Notice that the klm lines are calculated in the same space as the input control points.
169 // If you transform the points the lines will also need to be transformed. This can be done
170 // by mapping the lines with the inverse-transpose of the matrix used to map the points.
171 void getCubicKLM(const SkPoint p[4], SkScalar klm[9]);