cubic-map for non-linear t
Bug: skia:
Change-Id: I248864bd853361c1abfc2d8af61a27ab27a49a91
Reviewed-on: https://skia-review.googlesource.com/38882
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>
diff --git a/gm/aaclip.cpp b/gm/aaclip.cpp
index 0c90f53..129a952 100644
--- a/gm/aaclip.cpp
+++ b/gm/aaclip.cpp
@@ -11,6 +11,52 @@
#include "SkPath.h"
#include "SkMakeUnique.h"
+
+#include "SkCubicMap.h"
+
+static void test_cubic(SkCanvas* canvas) {
+ const SkPoint pts[] = {
+ { 0.333333f, 0.333333f }, { 0.666666f, 0.666666f },
+ { 1, 0 }, { 0, 1 },
+ { 0, 1 }, { 1, 0 },
+ { 0, 0 }, { 1, 1 },
+ { 1, 1 }, { 0, 0 },
+ { 0, 1 }, { 0, 1 },
+ { 1, 0 }, { 1, 0 },
+ };
+
+ SkPaint paint0, paint1;
+ paint0.setAntiAlias(true); paint0.setStrokeWidth(3/256.0f); paint0.setColor(SK_ColorRED);
+ paint1.setAntiAlias(true);
+
+ SkCubicMap cmap;
+
+ canvas->translate(10, 266);
+ canvas->scale(256, -256);
+ for (size_t i = 0; i < SK_ARRAY_COUNT(pts); i += 2) {
+ cmap.setPts(pts[i], pts[i+1]);
+
+ const int N = 128;
+ SkPoint tmp0[N+1], tmp1[N+1], tmp2[N+1];
+ for (int j = 0; j <= N; ++j) {
+ float p = j * 1.0f / N;
+ tmp0[j] = cmap.computeFromT(p);
+ tmp1[j].set(p, cmap.computeYFromX(p));
+ tmp2[j].set(p, cmap.hackYFromX(p));
+ }
+
+ canvas->save();
+ canvas->drawPoints(SkCanvas::kPolygon_PointMode, N+1, tmp0, paint0);
+ canvas->drawPoints(SkCanvas::kPolygon_PointMode, N+1, tmp1, paint1);
+ canvas->translate(0, -1.2f);
+ canvas->drawPoints(SkCanvas::kPolygon_PointMode, N+1, tmp0, paint0);
+ canvas->drawPoints(SkCanvas::kPolygon_PointMode, N+1, tmp2, paint1);
+ canvas->restore();
+
+ canvas->translate(1.1f, 0);
+ }
+}
+
static void do_draw(SkCanvas* canvas, const SkRect& r) {
SkPaint paint;
paint.setBlendMode(SkBlendMode::kSrc);
@@ -141,6 +187,8 @@
}
void onDraw(SkCanvas* canvas) override {
+ if (0) { test_cubic(canvas); return; }
+
// Initial pixel-boundary-aligned draw
draw_rect_tests(canvas);
diff --git a/gn/core.gni b/gn/core.gni
index 3a059fe..ad7c9a0 100644
--- a/gn/core.gni
+++ b/gn/core.gni
@@ -97,6 +97,8 @@
"$_src/core/SkCpu.h",
"$_src/core/SkCubicClipper.cpp",
"$_src/core/SkCubicClipper.h",
+ "$_src/core/SkCubicMap.cpp",
+ "$_src/core/SkCubicMap.h",
"$_src/core/SkData.cpp",
"$_src/core/SkDataTable.cpp",
"$_src/core/SkDebug.cpp",
diff --git a/src/core/SkCubicMap.cpp b/src/core/SkCubicMap.cpp
new file mode 100644
index 0000000..a95b548
--- /dev/null
+++ b/src/core/SkCubicMap.cpp
@@ -0,0 +1,83 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkCubicMap.h"
+#include "SkNx.h"
+#include "../../src/pathops/SkPathOpsCubic.h"
+
+void SkCubicMap::setPts(SkPoint p1, SkPoint p2) {
+ Sk2s s1 = Sk2s::Load(&p1) * 3;
+ Sk2s s2 = Sk2s::Load(&p2) * 3;
+
+ s1 = Sk2s::Min(Sk2s::Max(s1, 0), 3);
+ s2 = Sk2s::Min(Sk2s::Max(s2, 0), 3);
+
+ (Sk2s(1) + s1 - s2).store(&fCoeff[0]);
+ (s2 - s1 - s1).store(&fCoeff[1]);
+ s1.store(&fCoeff[2]);
+
+ this->buildXTable();
+}
+
+SkPoint SkCubicMap::computeFromT(float t) const {
+ Sk2s a = Sk2s::Load(&fCoeff[0]);
+ Sk2s b = Sk2s::Load(&fCoeff[1]);
+ Sk2s c = Sk2s::Load(&fCoeff[2]);
+
+ SkPoint result;
+ (((a * t + b) * t + c) * t).store(&result);
+ return result;
+}
+
+float SkCubicMap::computeYFromX(float x) const {
+ x = SkTPin<float>(x, 0, 0.99999f) * kTableCount;
+ float ix = sk_float_floor(x);
+ int index = (int)ix;
+ SkASSERT((unsigned)index < SK_ARRAY_COUNT(fXTable));
+ return this->computeFromT(fXTable[index].fT0 + fXTable[index].fDT * (x - ix)).fY;
+}
+
+float SkCubicMap::hackYFromX(float x) const {
+ x = SkTPin<float>(x, 0, 0.99999f) * kTableCount;
+ float ix = sk_float_floor(x);
+ int index = (int)ix;
+ SkASSERT((unsigned)index < SK_ARRAY_COUNT(fXTable));
+ return fXTable[index].fY0 + fXTable[index].fDY * (x - ix);
+}
+
+static float compute_t_from_x(float A, float B, float C, float x) {
+ double roots[3];
+ SkDEBUGCODE(int count =) SkDCubic::RootsValidT(A, B, C, -x, roots);
+ SkASSERT(count == 1);
+ return (float)roots[0];
+}
+
+void SkCubicMap::buildXTable() {
+ float prevT = 0;
+
+ const float dx = 1.0f / kTableCount;
+ float x = dx;
+
+ fXTable[0].fT0 = 0;
+ fXTable[0].fY0 = 0;
+ for (int i = 1; i < kTableCount; ++i) {
+ float t = compute_t_from_x(fCoeff[0].fX, fCoeff[1].fX, fCoeff[2].fX, x);
+ SkASSERT(t > prevT);
+
+ fXTable[i - 1].fDT = t - prevT;
+ fXTable[i].fT0 = t;
+
+ SkPoint p = this->computeFromT(t);
+ fXTable[i - 1].fDY = p.fY - fXTable[i - 1].fY0;
+ fXTable[i].fY0 = p.fY;
+
+ prevT = t;
+ x += dx;
+ }
+ fXTable[kTableCount - 1].fDT = 1 - prevT;
+ fXTable[kTableCount - 1].fDY = 1 - fXTable[kTableCount - 1].fY0;
+}
diff --git a/src/core/SkCubicMap.h b/src/core/SkCubicMap.h
new file mode 100644
index 0000000..bd372e0
--- /dev/null
+++ b/src/core/SkCubicMap.h
@@ -0,0 +1,42 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkCubicMap_DEFINED
+#define SkCubicMap_DEFINED
+
+#include "SkPoint.h"
+
+class SkCubicMap {
+public:
+ void setPts(SkPoint p1, SkPoint p2);
+ void setPts(float x1, float y1, float x2, float y2) {
+ this->setPts({x1, y1}, {x2, y2});
+ }
+
+ SkPoint computeFromT(float t) const;
+ float computeYFromX(float x) const;
+
+ // experimental
+ float hackYFromX(float x) const;
+
+private:
+ SkPoint fCoeff[4];
+ // x->t lookup
+ enum { kTableCount = 16 };
+ struct Rec {
+ float fT0;
+ float fDT;
+
+ float fY0;
+ float fDY;
+ };
+ Rec fXTable[kTableCount];
+
+ void buildXTable();
+};
+#endif
+