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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 "src/utils/SkPatchUtils.h"
- #include "include/private/SkColorData.h"
- #include "include/private/SkTo.h"
- #include "src/core/SkArenaAlloc.h"
- #include "src/core/SkColorSpacePriv.h"
- #include "src/core/SkConvertPixels.h"
- #include "src/core/SkGeometry.h"
- namespace {
- enum CubicCtrlPts {
- kTopP0_CubicCtrlPts = 0,
- kTopP1_CubicCtrlPts = 1,
- kTopP2_CubicCtrlPts = 2,
- kTopP3_CubicCtrlPts = 3,
- kRightP0_CubicCtrlPts = 3,
- kRightP1_CubicCtrlPts = 4,
- kRightP2_CubicCtrlPts = 5,
- kRightP3_CubicCtrlPts = 6,
- kBottomP0_CubicCtrlPts = 9,
- kBottomP1_CubicCtrlPts = 8,
- kBottomP2_CubicCtrlPts = 7,
- kBottomP3_CubicCtrlPts = 6,
- kLeftP0_CubicCtrlPts = 0,
- kLeftP1_CubicCtrlPts = 11,
- kLeftP2_CubicCtrlPts = 10,
- kLeftP3_CubicCtrlPts = 9,
- };
- // Enum for corner also clockwise.
- enum Corner {
- kTopLeft_Corner = 0,
- kTopRight_Corner,
- kBottomRight_Corner,
- kBottomLeft_Corner
- };
- }
- /**
- * 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:
- /**
- * Receives the 4 control points of the cubic bezier.
- */
- explicit FwDCubicEvaluator(const SkPoint points[4])
- : fCoefs(points) {
- memcpy(fPoints, points, 4 * sizeof(SkPoint));
- this->restart(1);
- }
- /**
- * Restarts the forward differences evaluator to the first value of t = 0.
- */
- void restart(int divisions) {
- fDivisions = divisions;
- fCurrent = 0;
- fMax = fDivisions + 1;
- Sk2s h = Sk2s(1.f / fDivisions);
- Sk2s h2 = h * h;
- Sk2s h3 = h2 * h;
- Sk2s fwDiff3 = Sk2s(6) * fCoefs.fA * h3;
- fFwDiff[3] = to_point(fwDiff3);
- fFwDiff[2] = to_point(fwDiff3 + times_2(fCoefs.fB) * h2);
- fFwDiff[1] = to_point(fCoefs.fA * h3 + fCoefs.fB * h2 + fCoefs.fC * h);
- fFwDiff[0] = to_point(fCoefs.fD);
- }
- /**
- * 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:
- SkCubicCoeff fCoefs;
- int fMax, fCurrent, fDivisions;
- SkPoint fFwDiff[4], fPoints[4];
- };
- ////////////////////////////////////////////////////////////////////////////////
- // size in pixels of each partition per axis, adjust this knob
- static const int kPartitionSize = 10;
- /**
- * Calculate the approximate arc length given a bezier curve's control points.
- * Returns -1 if bad calc (i.e. non-finite)
- */
- static SkScalar approx_arc_length(const SkPoint points[], int count) {
- if (count < 2) {
- return 0;
- }
- SkScalar arcLength = 0;
- for (int i = 0; i < count - 1; i++) {
- arcLength += SkPoint::Distance(points[i], points[i + 1]);
- }
- return SkScalarIsFinite(arcLength) ? arcLength : -1;
- }
- static SkScalar bilerp(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 a * (1.f - ty) + b * ty;
- }
- static Sk4f bilerp(SkScalar tx, SkScalar ty,
- const Sk4f& c00, const Sk4f& c10, const Sk4f& c01, const Sk4f& c11) {
- Sk4f a = c00 * (1.f - tx) + c10 * tx;
- Sk4f b = c01 * (1.f - tx) + c11 * tx;
- return a * (1.f - ty) + b * ty;
- }
- SkISize SkPatchUtils::GetLevelOfDetail(const SkPoint cubics[12], const SkMatrix* matrix) {
- // Approximate length of each cubic.
- SkPoint pts[kNumPtsCubic];
- SkPatchUtils::GetTopCubic(cubics, pts);
- matrix->mapPoints(pts, kNumPtsCubic);
- SkScalar topLength = approx_arc_length(pts, kNumPtsCubic);
- SkPatchUtils::GetBottomCubic(cubics, pts);
- matrix->mapPoints(pts, kNumPtsCubic);
- SkScalar bottomLength = approx_arc_length(pts, kNumPtsCubic);
- SkPatchUtils::GetLeftCubic(cubics, pts);
- matrix->mapPoints(pts, kNumPtsCubic);
- SkScalar leftLength = approx_arc_length(pts, kNumPtsCubic);
- SkPatchUtils::GetRightCubic(cubics, pts);
- matrix->mapPoints(pts, kNumPtsCubic);
- SkScalar rightLength = approx_arc_length(pts, kNumPtsCubic);
- if (topLength < 0 || bottomLength < 0 || leftLength < 0 || rightLength < 0) {
- return {0, 0}; // negative length is a sentinel for bad length (i.e. non-finite)
- }
- // Level of detail per axis, based on the larger side between top and bottom or left and right
- int lodX = static_cast<int>(SkMaxScalar(topLength, bottomLength) / kPartitionSize);
- int lodY = static_cast<int>(SkMaxScalar(leftLength, rightLength) / kPartitionSize);
- return SkISize::Make(SkMax32(8, lodX), SkMax32(8, lodY));
- }
- void SkPatchUtils::GetTopCubic(const SkPoint cubics[12], SkPoint points[4]) {
- points[0] = cubics[kTopP0_CubicCtrlPts];
- points[1] = cubics[kTopP1_CubicCtrlPts];
- points[2] = cubics[kTopP2_CubicCtrlPts];
- points[3] = cubics[kTopP3_CubicCtrlPts];
- }
- void SkPatchUtils::GetBottomCubic(const SkPoint cubics[12], SkPoint points[4]) {
- points[0] = cubics[kBottomP0_CubicCtrlPts];
- points[1] = cubics[kBottomP1_CubicCtrlPts];
- points[2] = cubics[kBottomP2_CubicCtrlPts];
- points[3] = cubics[kBottomP3_CubicCtrlPts];
- }
- void SkPatchUtils::GetLeftCubic(const SkPoint cubics[12], SkPoint points[4]) {
- points[0] = cubics[kLeftP0_CubicCtrlPts];
- points[1] = cubics[kLeftP1_CubicCtrlPts];
- points[2] = cubics[kLeftP2_CubicCtrlPts];
- points[3] = cubics[kLeftP3_CubicCtrlPts];
- }
- void SkPatchUtils::GetRightCubic(const SkPoint cubics[12], SkPoint points[4]) {
- points[0] = cubics[kRightP0_CubicCtrlPts];
- points[1] = cubics[kRightP1_CubicCtrlPts];
- points[2] = cubics[kRightP2_CubicCtrlPts];
- points[3] = cubics[kRightP3_CubicCtrlPts];
- }
- static void skcolor_to_float(SkPMColor4f* dst, const SkColor* src, int count, SkColorSpace* dstCS) {
- SkImageInfo srcInfo = SkImageInfo::Make(count, 1, kBGRA_8888_SkColorType,
- kUnpremul_SkAlphaType, SkColorSpace::MakeSRGB());
- SkImageInfo dstInfo = SkImageInfo::Make(count, 1, kRGBA_F32_SkColorType,
- kPremul_SkAlphaType, sk_ref_sp(dstCS));
- SkConvertPixels(dstInfo, dst, 0, srcInfo, src, 0);
- }
- static void float_to_skcolor(SkColor* dst, const SkPMColor4f* src, int count, SkColorSpace* srcCS) {
- SkImageInfo srcInfo = SkImageInfo::Make(count, 1, kRGBA_F32_SkColorType,
- kPremul_SkAlphaType, sk_ref_sp(srcCS));
- SkImageInfo dstInfo = SkImageInfo::Make(count, 1, kBGRA_8888_SkColorType,
- kUnpremul_SkAlphaType, SkColorSpace::MakeSRGB());
- SkConvertPixels(dstInfo, dst, 0, srcInfo, src, 0);
- }
- sk_sp<SkVertices> SkPatchUtils::MakeVertices(const SkPoint cubics[12], const SkColor srcColors[4],
- const SkPoint srcTexCoords[4], int lodX, int lodY,
- SkColorSpace* colorSpace) {
- if (lodX < 1 || lodY < 1 || nullptr == cubics) {
- return nullptr;
- }
- // check for overflow in multiplication
- const int64_t lodX64 = (lodX + 1),
- lodY64 = (lodY + 1),
- mult64 = lodX64 * lodY64;
- if (mult64 > SK_MaxS32) {
- return nullptr;
- }
- // Treat null interpolation space as sRGB.
- if (!colorSpace) {
- colorSpace = sk_srgb_singleton();
- }
- int vertexCount = SkToS32(mult64);
- // it is recommended to generate draw calls of no more than 65536 indices, so we never generate
- // more than 60000 indices. To accomplish that we resize the LOD and vertex count
- if (vertexCount > 10000 || lodX > 200 || lodY > 200) {
- float weightX = static_cast<float>(lodX) / (lodX + lodY);
- float weightY = static_cast<float>(lodY) / (lodX + lodY);
- // 200 comes from the 100 * 2 which is the max value of vertices because of the limit of
- // 60000 indices ( sqrt(60000 / 6) that comes from data->fIndexCount = lodX * lodY * 6)
- // Need a min of 1 since we later divide by lod
- lodX = std::max(1, sk_float_floor2int_no_saturate(weightX * 200));
- lodY = std::max(1, sk_float_floor2int_no_saturate(weightY * 200));
- vertexCount = (lodX + 1) * (lodY + 1);
- }
- const int indexCount = lodX * lodY * 6;
- uint32_t flags = 0;
- if (srcTexCoords) {
- flags |= SkVertices::kHasTexCoords_BuilderFlag;
- }
- if (srcColors) {
- flags |= SkVertices::kHasColors_BuilderFlag;
- }
- SkSTArenaAlloc<2048> alloc;
- SkPMColor4f* cornerColors = srcColors ? alloc.makeArray<SkPMColor4f>(4) : nullptr;
- SkPMColor4f* tmpColors = srcColors ? alloc.makeArray<SkPMColor4f>(vertexCount) : nullptr;
- SkVertices::Builder builder(SkVertices::kTriangles_VertexMode, vertexCount, indexCount, flags);
- SkPoint* pos = builder.positions();
- SkPoint* texs = builder.texCoords();
- uint16_t* indices = builder.indices();
- if (cornerColors) {
- skcolor_to_float(cornerColors, srcColors, kNumCorners, colorSpace);
- }
- SkPoint pts[kNumPtsCubic];
- SkPatchUtils::GetBottomCubic(cubics, pts);
- FwDCubicEvaluator fBottom(pts);
- SkPatchUtils::GetTopCubic(cubics, pts);
- FwDCubicEvaluator fTop(pts);
- SkPatchUtils::GetLeftCubic(cubics, pts);
- FwDCubicEvaluator fLeft(pts);
- SkPatchUtils::GetRightCubic(cubics, pts);
- FwDCubicEvaluator fRight(pts);
- fBottom.restart(lodX);
- fTop.restart(lodX);
- SkScalar u = 0.0f;
- int stride = lodY + 1;
- for (int x = 0; x <= lodX; x++) {
- SkPoint bottom = fBottom.next(), top = fTop.next();
- fLeft.restart(lodY);
- fRight.restart(lodY);
- SkScalar v = 0.f;
- for (int y = 0; y <= lodY; y++) {
- int dataIndex = x * (lodY + 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()));
- pos[dataIndex] = s0 + s1 - s2;
- if (cornerColors) {
- bilerp(u, v, Sk4f::Load(cornerColors[kTopLeft_Corner].vec()),
- Sk4f::Load(cornerColors[kTopRight_Corner].vec()),
- Sk4f::Load(cornerColors[kBottomLeft_Corner].vec()),
- Sk4f::Load(cornerColors[kBottomRight_Corner].vec()))
- .store(tmpColors[dataIndex].vec());
- }
- if (texs) {
- texs[dataIndex] = SkPoint::Make(bilerp(u, v, srcTexCoords[kTopLeft_Corner].x(),
- srcTexCoords[kTopRight_Corner].x(),
- srcTexCoords[kBottomLeft_Corner].x(),
- srcTexCoords[kBottomRight_Corner].x()),
- bilerp(u, v, srcTexCoords[kTopLeft_Corner].y(),
- srcTexCoords[kTopRight_Corner].y(),
- srcTexCoords[kBottomLeft_Corner].y(),
- srcTexCoords[kBottomRight_Corner].y()));
- }
- if(x < lodX && y < lodY) {
- int i = 6 * (x * lodY + y);
- indices[i] = x * stride + y;
- indices[i + 1] = x * stride + 1 + y;
- indices[i + 2] = (x + 1) * stride + 1 + y;
- indices[i + 3] = indices[i];
- indices[i + 4] = indices[i + 2];
- indices[i + 5] = (x + 1) * stride + y;
- }
- v = SkScalarClampMax(v + 1.f / lodY, 1);
- }
- u = SkScalarClampMax(u + 1.f / lodX, 1);
- }
- if (tmpColors) {
- float_to_skcolor(builder.colors(), tmpColors, vertexCount, colorSpace);
- }
- return builder.detach();
- }
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