diff -r 000000000000 -r 6474c204b198 gfx/skia/trunk/src/gpu/GrPathUtils.h --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/gfx/skia/trunk/src/gpu/GrPathUtils.h Wed Dec 31 06:09:35 2014 +0100 @@ -0,0 +1,173 @@ +/* + * Copyright 2011 Google Inc. + * + * Use of this source code is governed by a BSD-style license that can be + * found in the LICENSE file. + */ + +#ifndef GrPathUtils_DEFINED +#define GrPathUtils_DEFINED + +#include "GrPoint.h" +#include "SkRect.h" +#include "SkPath.h" +#include "SkTArray.h" + +class SkMatrix; + +/** + * Utilities for evaluating paths. + */ +namespace GrPathUtils { + SkScalar scaleToleranceToSrc(SkScalar devTol, + const SkMatrix& viewM, + const SkRect& pathBounds); + + /// Since we divide by tol if we're computing exact worst-case bounds, + /// very small tolerances will be increased to gMinCurveTol. + int worstCasePointCount(const SkPath&, + int* subpaths, + SkScalar tol); + + /// Since we divide by tol if we're computing exact worst-case bounds, + /// very small tolerances will be increased to gMinCurveTol. + uint32_t quadraticPointCount(const GrPoint points[], SkScalar tol); + + uint32_t generateQuadraticPoints(const GrPoint& p0, + const GrPoint& p1, + const GrPoint& p2, + SkScalar tolSqd, + GrPoint** points, + uint32_t pointsLeft); + + /// Since we divide by tol if we're computing exact worst-case bounds, + /// very small tolerances will be increased to gMinCurveTol. + uint32_t cubicPointCount(const GrPoint points[], SkScalar tol); + + uint32_t generateCubicPoints(const GrPoint& p0, + const GrPoint& p1, + const GrPoint& p2, + const GrPoint& p3, + SkScalar tolSqd, + GrPoint** points, + uint32_t pointsLeft); + + // A 2x3 matrix that goes from the 2d space coordinates to UV space where + // u^2-v = 0 specifies the quad. The matrix is determined by the control + // points of the quadratic. + class QuadUVMatrix { + public: + QuadUVMatrix() {}; + // Initialize the matrix from the control pts + QuadUVMatrix(const GrPoint controlPts[3]) { this->set(controlPts); } + void set(const GrPoint controlPts[3]); + + /** + * Applies the matrix to vertex positions to compute UV coords. This + * has been templated so that the compiler can easliy unroll the loop + * and reorder to avoid stalling for loads. The assumption is that a + * path renderer will have a small fixed number of vertices that it + * uploads for each quad. + * + * N is the number of vertices. + * STRIDE is the size of each vertex. + * UV_OFFSET is the offset of the UV values within each vertex. + * vertices is a pointer to the first vertex. + */ + template + void apply(const void* vertices) { + intptr_t xyPtr = reinterpret_cast(vertices); + intptr_t uvPtr = reinterpret_cast(vertices) + UV_OFFSET; + float sx = fM[0]; + float kx = fM[1]; + float tx = fM[2]; + float ky = fM[3]; + float sy = fM[4]; + float ty = fM[5]; + for (int i = 0; i < N; ++i) { + const GrPoint* xy = reinterpret_cast(xyPtr); + GrPoint* uv = reinterpret_cast(uvPtr); + uv->fX = sx * xy->fX + kx * xy->fY + tx; + uv->fY = ky * xy->fX + sy * xy->fY + ty; + xyPtr += STRIDE; + uvPtr += STRIDE; + } + } + private: + float fM[6]; + }; + + // Input is 3 control points and a weight for a bezier conic. Calculates the + // three linear functionals (K,L,M) that represent the implicit equation of the + // conic, K^2 - LM. + // + // Output: + // K = (klm[0], klm[1], klm[2]) + // L = (klm[3], klm[4], klm[5]) + // M = (klm[6], klm[7], klm[8]) + void getConicKLM(const SkPoint p[3], const SkScalar weight, SkScalar klm[9]); + + // Converts a cubic into a sequence of quads. If working in device space + // use tolScale = 1, otherwise set based on stretchiness of the matrix. The + // result is sets of 3 points in quads (TODO: share endpoints in returned + // array) + // When we approximate a cubic {a,b,c,d} with a quadratic we may have to + // ensure that the new control point lies between the lines ab and cd. The + // convex path renderer requires this. It starts with a path where all the + // control points taken together form a convex polygon. It relies on this + // property and the quadratic approximation of cubics step cannot alter it. + // Setting constrainWithinTangents to true enforces this property. When this + // is true the cubic must be simple and dir must specify the orientation of + // the cubic. Otherwise, dir is ignored. + void convertCubicToQuads(const GrPoint p[4], + SkScalar tolScale, + bool constrainWithinTangents, + SkPath::Direction dir, + SkTArray* quads); + + // Chops the cubic bezier passed in by src, at the double point (intersection point) + // if the curve is a cubic loop. If it is a loop, there will be two parametric values for + // the double point: ls and ms. We chop the cubic at these values if they are between 0 and 1. + // Return value: + // Value of 3: ls and ms are both between (0,1), and dst will contain the three cubics, + // dst[0..3], dst[3..6], and dst[6..9] if dst is not NULL + // Value of 2: Only one of ls and ms are between (0,1), and dst will contain the two cubics, + // dst[0..3] and dst[3..6] if dst is not NULL + // Value of 1: Neither ls or ms are between (0,1), and dst will contain the one original cubic, + // dst[0..3] if dst is not NULL + // + // Optional KLM Calculation: + // The function can also return the KLM linear functionals for the chopped cubic implicit form + // of K^3 - LM. + // It will calculate a single set of KLM values that can be shared by all sub cubics, except + // for the subsection that is "the loop" the K and L values need to be negated. + // Output: + // klm: Holds the values for the linear functionals as: + // K = (klm[0], klm[1], klm[2]) + // L = (klm[3], klm[4], klm[5]) + // M = (klm[6], klm[7], klm[8]) + // klm_rev: These values are flags for the corresponding sub cubic saying whether or not + // the K and L values need to be flipped. A value of -1.f means flip K and L and + // a value of 1.f means do nothing. + // *****DO NOT FLIP M, JUST K AND L***** + // + // Notice that the klm lines are calculated in the same space as the input control points. + // If you transform the points the lines will also need to be transformed. This can be done + // by mapping the lines with the inverse-transpose of the matrix used to map the points. + int chopCubicAtLoopIntersection(const SkPoint src[4], SkPoint dst[10] = NULL, + SkScalar klm[9] = NULL, SkScalar klm_rev[3] = NULL); + + // Input is p which holds the 4 control points of a non-rational cubic Bezier curve. + // Output is the coefficients of the three linear functionals K, L, & M which + // represent the implicit form of the cubic as f(x,y,w) = K^3 - LM. The w term + // will always be 1. The output is stored in the array klm, where the values are: + // K = (klm[0], klm[1], klm[2]) + // L = (klm[3], klm[4], klm[5]) + // M = (klm[6], klm[7], klm[8]) + // + // Notice that the klm lines are calculated in the same space as the input control points. + // If you transform the points the lines will also need to be transformed. This can be done + // by mapping the lines with the inverse-transpose of the matrix used to map the points. + void getCubicKLM(const SkPoint p[4], SkScalar klm[9]); +}; +#endif