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diff --git a/src/core/SkPatch.cpp b/src/core/SkPatch.cpp
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+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkPatch.h"
+
+#include "SkGeometry.h"
+#include "SkColorPriv.h"
+
+////////////////////////////////////////////////////////////////////////////////
+
+/**
+ * Evaluator to sample the values of a cubic bezier using forward differences.
+ * Forward differences is a method for evaluating a nth degree polynomial at a uniform step by only
+ * adding precalculated values.
+ * For a linear example we have the function f(t) = m*t+b, then the value of that function at t+h
+ * would be f(t+h) = m*(t+h)+b. If we want to know the uniform step that we must add to the first
+ * evaluation f(t) then we need to substract f(t+h) - f(t) = m*t + m*h + b - m*t + b = mh. After
+ * obtaining this value (mh) we could just add this constant step to our first sampled point
+ * to compute the next one.
+ *
+ * For the cubic case the first difference gives as a result a quadratic polynomial to which we can
+ * apply again forward differences and get linear function to which we can apply again forward
+ * differences to get a constant difference. This is why we keep an array of size 4, the 0th
+ * position keeps the sampled value while the next ones keep the quadratic, linear and constant
+ * difference values.
+ */
+
+class FwDCubicEvaluator {
+
+public:
+ FwDCubicEvaluator() { }
+
+ /**
+ * Receives the 4 control points of the cubic bezier.
+ */
+ FwDCubicEvaluator(SkPoint a, SkPoint b, SkPoint c, SkPoint d) {
+ fPoints[0] = a;
+ fPoints[1] = b;
+ fPoints[2] = c;
+ fPoints[3] = d;
+
+ SkScalar cx[4], cy[4];
+ SkGetCubicCoeff(fPoints, cx, cy);
+ fCoefs[0].set(cx[0], cy[0]);
+ fCoefs[1].set(cx[1], cy[1]);
+ fCoefs[2].set(cx[2], cy[2]);
+ fCoefs[3].set(cx[3], cy[3]);
+
+ this->restart(1);
+ }
+
+ /**
+ * Restarts the forward differences evaluator to the first value of t = 0.
+ */
+ void restart(int divisions) {
+ fDivisions = divisions;
+ SkScalar h = 1.f / fDivisions;
+ fCurrent = 0;
+ fMax = fDivisions + 1;
+ fFwDiff[0] = fCoefs[3];
+ SkScalar h2 = h * h;
+ SkScalar h3 = h2 * h;
+
+ fFwDiff[3].set(6.f * fCoefs[0].x() * h3, 6.f * fCoefs[0].y() * h3); //6ah^3
+ fFwDiff[2].set(fFwDiff[3].x() + 2.f * fCoefs[1].x() * h2, //6ah^3 + 2bh^2
+ fFwDiff[3].y() + 2.f * fCoefs[1].y() * h2);
+ fFwDiff[1].set(fCoefs[0].x() * h3 + fCoefs[1].x() * h2 + fCoefs[2].x() * h,//ah^3 + bh^2 +ch
+ fCoefs[0].y() * h3 + fCoefs[1].y() * h2 + fCoefs[2].y() * h);
+ }
+
+ /**
+ * Check if the evaluator is still within the range of 0<=t<=1
+ */
+ bool done() const {
+ return fCurrent > fMax;
+ }
+
+ /**
+ * Call next to obtain the SkPoint sampled and move to the next one.
+ */
+ SkPoint next() {
+ SkPoint point = fFwDiff[0];
+ fFwDiff[0] += fFwDiff[1];
+ fFwDiff[1] += fFwDiff[2];
+ fFwDiff[2] += fFwDiff[3];
+ fCurrent++;
+ return point;
+ }
+
+ const SkPoint* getCtrlPoints() const {
+ return fPoints;
+ }
+
+private:
+ int fMax, fCurrent, fDivisions;
+ SkPoint fFwDiff[4], fCoefs[4], fPoints[4];
+};
+
+////////////////////////////////////////////////////////////////////////////////
+
+SkPatch::SkPatch(SkPoint points[12], SkColor colors[4]) {
+
+ for (int i = 0; i<12; i++) {
+ fCtrlPoints[i] = points[i];
+ }
+
+ fCornerColors[0] = SkPreMultiplyColor(colors[0]);
+ fCornerColors[1] = SkPreMultiplyColor(colors[1]);
+ fCornerColors[2] = SkPreMultiplyColor(colors[2]);
+ fCornerColors[3] = SkPreMultiplyColor(colors[3]);
+}
+
+uint8_t bilinear(SkScalar tx, SkScalar ty, SkScalar c00, SkScalar c10, SkScalar c01, SkScalar c11) {
+ SkScalar a = c00 * (1.f - tx) + c10 * tx;
+ SkScalar b = c01 * (1.f - tx) + c11 * tx;
+ return uint8_t(a * (1.f - ty) + b * ty);
+}
+
+bool SkPatch::getVertexData(SkPatch::VertexData* data, int divisions) {
+
+ if (divisions < 1) {
+ return false;
+ }
+
+ int divX = divisions, divY = divisions;
+
+ data->fVertexCount = (divX + 1) * (divY + 1);
+ data->fIndexCount = divX * divY * 6;
+
+ data->fPoints = SkNEW_ARRAY(SkPoint, data->fVertexCount);
+ data->fColors = SkNEW_ARRAY(uint32_t, data->fVertexCount);
+ data->fTexCoords = SkNEW_ARRAY(SkPoint, data->fVertexCount);
+ data->fIndices = SkNEW_ARRAY(uint16_t, data->fIndexCount);
+
+ FwDCubicEvaluator fBottom(fCtrlPoints[kBottomP0_CubicCtrlPts],
+ fCtrlPoints[kBottomP1_CubicCtrlPts],
+ fCtrlPoints[kBottomP2_CubicCtrlPts],
+ fCtrlPoints[kBottomP3_CubicCtrlPts]),
+ fTop(fCtrlPoints[kTopP0_CubicCtrlPts],
+ fCtrlPoints[kTopP1_CubicCtrlPts],
+ fCtrlPoints[kTopP2_CubicCtrlPts],
+ fCtrlPoints[kTopP2_CubicCtrlPts]),
+ fLeft(fCtrlPoints[kLeftP0_CubicCtrlPts],
+ fCtrlPoints[kLeftP1_CubicCtrlPts],
+ fCtrlPoints[kLeftP2_CubicCtrlPts],
+ fCtrlPoints[kLeftP3_CubicCtrlPts]),
+ fRight(fCtrlPoints[kRightP0_CubicCtrlPts],
+ fCtrlPoints[kRightP1_CubicCtrlPts],
+ fCtrlPoints[kRightP2_CubicCtrlPts],
+ fCtrlPoints[kRightP3_CubicCtrlPts]);
+
+ fBottom.restart(divX);
+ fTop.restart(divX);
+
+ SkScalar u = 0.0f;
+ int stride = divY + 1;
+ for (int x = 0; x <= divX; x++) {
+ SkPoint bottom = fBottom.next(), top = fTop.next();
+ fLeft.restart(divY);
+ fRight.restart(divY);
+ SkScalar v = 0.f;
+ for (int y = 0; y <= divY; y++) {
+ int dataIndex = x * (divX + 1) + y;
+
+ SkPoint left = fLeft.next(), right = fRight.next();
+
+ SkPoint s0 = SkPoint::Make((1.0f - v) * top.x() + v * bottom.x(),
+ (1.0f - v) * top.y() + v * bottom.y());
+ SkPoint s1 = SkPoint::Make((1.0f - u) * left.x() + u * right.x(),
+ (1.0f - u) * left.y() + u * right.y());
+ SkPoint s2 = SkPoint::Make(
+ (1.0f - v) * ((1.0f - u) * fTop.getCtrlPoints()[0].x()
+ + u * fTop.getCtrlPoints()[3].x())
+ + v * ((1.0f - u) * fBottom.getCtrlPoints()[0].x()
+ + u * fBottom.getCtrlPoints()[3].x()),
+ (1.0f - v) * ((1.0f - u) * fTop.getCtrlPoints()[0].y()
+ + u * fTop.getCtrlPoints()[3].y())
+ + v * ((1.0f - u) * fBottom.getCtrlPoints()[0].y()
+ + u * fBottom.getCtrlPoints()[3].y()));
+ data->fPoints[dataIndex] = s0 + s1 - s2;
+
+ uint8_t a = bilinear(u, v,
+ SkScalar(SkColorGetA(fCornerColors[0])),
+ SkScalar(SkColorGetA(fCornerColors[1])),
+ SkScalar(SkColorGetA(fCornerColors[2])),
+ SkScalar(SkColorGetA(fCornerColors[3])));
+ uint8_t r = bilinear(u, v,
+ SkScalar(SkColorGetR(fCornerColors[0])),
+ SkScalar(SkColorGetR(fCornerColors[1])),
+ SkScalar(SkColorGetR(fCornerColors[2])),
+ SkScalar(SkColorGetR(fCornerColors[3])));
+ uint8_t g = bilinear(u, v,
+ SkScalar(SkColorGetG(fCornerColors[0])),
+ SkScalar(SkColorGetG(fCornerColors[1])),
+ SkScalar(SkColorGetG(fCornerColors[2])),
+ SkScalar(SkColorGetG(fCornerColors[3])));
+ uint8_t b = bilinear(u, v,
+ SkScalar(SkColorGetB(fCornerColors[0])),
+ SkScalar(SkColorGetB(fCornerColors[1])),
+ SkScalar(SkColorGetB(fCornerColors[2])),
+ SkScalar(SkColorGetB(fCornerColors[3])));
+ data->fColors[dataIndex] = SkPackARGB32(a,r,g,b);
+
+ data->fTexCoords[dataIndex] = SkPoint::Make(u, v);
+
+ if(x < divX && y < divY) {
+ int i = 6 * (x * divY + y);
+ data->fIndices[i] = x * stride + y;
+ data->fIndices[i + 1] = x * stride + 1 + y;
+ data->fIndices[i + 2] = (x + 1) * stride + 1 + y;
+ data->fIndices[i + 3] = data->fIndices[i];
+ data->fIndices[i + 4] = data->fIndices[i + 2];
+ data->fIndices[i + 5] = (x + 1) * stride + y;
+ }
+ v += 1.f / divY;
+ }
+ u += 1.f / divX;
+ }
+ return true;
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-07-08 06:56:57 +0000