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skia2/samplecode/SampleClip.cpp
Mike Reed 63edc57c97 restructure EdgeClipper to accommodate other callers (e.g. half-plane) 
This allows us to clip a path against a half-plane (an arbitrary
diagonal line), in an effort to handle perspective correctly with
the near-plane.

Change-Id: I2082a750acf858340e4500ad46cf581472cefc6b
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/253996
Commit-Queue: Mike Reed <reed@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
2019-11-18 18:22:19 +00:00

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/*
* Copyright 2011 Google Inc.
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#include "include/core/SkCanvas.h"
#include "include/core/SkColorPriv.h"
#include "include/core/SkFont.h"
#include "include/core/SkPaint.h"
#include "include/core/SkPath.h"
#include "include/utils/SkRandom.h"
#include "samplecode/Sample.h"
#include "src/core/SkClipOpPriv.h"
constexpr int W = 150;
constexpr int H = 200;
static void show_text(SkCanvas* canvas, bool doAA) {
SkRandom rand;
SkPaint paint;
SkFont font(nullptr, 20);
font.setEdging(doAA ? SkFont::Edging::kSubpixelAntiAlias : SkFont::Edging::kAlias);
for (int i = 0; i < 200; ++i) {
paint.setColor((SK_A32_MASK << SK_A32_SHIFT) | rand.nextU());
canvas->drawString("Hamburgefons", rand.nextSScalar1() * W, rand.nextSScalar1() * H + 20,
font, paint);
}
}
static void show_fill(SkCanvas* canvas, bool doAA) {
SkRandom rand;
SkPaint paint;
paint.setAntiAlias(doAA);
for (int i = 0; i < 50; ++i) {
SkRect r;
SkPath p;
r.setXYWH(rand.nextSScalar1() * W, rand.nextSScalar1() * H,
rand.nextUScalar1() * W, rand.nextUScalar1() * H);
paint.setColor(rand.nextU());
canvas->drawRect(r, paint);
r.setXYWH(rand.nextSScalar1() * W, rand.nextSScalar1() * H,
rand.nextUScalar1() * W, rand.nextUScalar1() * H);
paint.setColor(rand.nextU());
p.addOval(r);
canvas->drawPath(p, paint);
}
}
static SkScalar randRange(SkRandom& rand, SkScalar min, SkScalar max) {
SkASSERT(min <= max);
return min + rand.nextUScalar1() * (max - min);
}
static void show_stroke(SkCanvas* canvas, bool doAA, SkScalar strokeWidth, int n) {
SkRandom rand;
SkPaint paint;
paint.setAntiAlias(doAA);
paint.setStyle(SkPaint::kStroke_Style);
paint.setStrokeWidth(strokeWidth);
for (int i = 0; i < n; ++i) {
SkRect r;
SkPath p;
r.setXYWH(rand.nextSScalar1() * W, rand.nextSScalar1() * H,
rand.nextUScalar1() * W, rand.nextUScalar1() * H);
paint.setColor(rand.nextU());
canvas->drawRect(r, paint);
r.setXYWH(rand.nextSScalar1() * W, rand.nextSScalar1() * H,
rand.nextUScalar1() * W, rand.nextUScalar1() * H);
paint.setColor(rand.nextU());
p.addOval(r);
canvas->drawPath(p, paint);
const SkScalar minx = -SkIntToScalar(W)/4;
const SkScalar maxx = 5*SkIntToScalar(W)/4;
const SkScalar miny = -SkIntToScalar(H)/4;
const SkScalar maxy = 5*SkIntToScalar(H)/4;
paint.setColor(rand.nextU());
canvas->drawLine(randRange(rand, minx, maxx), randRange(rand, miny, maxy),
randRange(rand, minx, maxx), randRange(rand, miny, maxy),
paint);
}
}
static void show_hair(SkCanvas* canvas, bool doAA) {
show_stroke(canvas, doAA, 0, 150);
}
static void show_thick(SkCanvas* canvas, bool doAA) {
show_stroke(canvas, doAA, SkIntToScalar(5), 50);
}
typedef void (*CanvasProc)(SkCanvas*, bool);
class ClipView : public Sample {
SkString name() override { return SkString("Clip"); }
void onDrawContent(SkCanvas* canvas) override {
canvas->drawColor(SK_ColorWHITE);
canvas->translate(SkIntToScalar(20), SkIntToScalar(20));
static const CanvasProc gProc[] = {
show_text, show_thick, show_hair, show_fill
};
SkRect r = { 0, 0, SkIntToScalar(W), SkIntToScalar(H) };
SkPath clipPath;
r.inset(SK_Scalar1 / 4, SK_Scalar1 / 4);
clipPath.addRoundRect(r, SkIntToScalar(20), SkIntToScalar(20));
// clipPath.toggleInverseFillType();
for (int aa = 0; aa <= 1; ++aa) {
canvas->save();
for (size_t i = 0; i < SK_ARRAY_COUNT(gProc); ++i) {
canvas->save();
canvas->clipPath(clipPath, kIntersect_SkClipOp, SkToBool(aa));
// canvas->drawColor(SK_ColorWHITE);
gProc[i](canvas, SkToBool(aa));
canvas->restore();
canvas->translate(W * SK_Scalar1 * 8 / 7, 0);
}
canvas->restore();
canvas->translate(0, H * SK_Scalar1 * 8 / 7);
}
}
};
DEF_SAMPLE( return new ClipView(); )
///////////////////////////////////////////////////////////////////////////////
struct SkHalfPlane {
SkScalar fA, fB, fC;
SkScalar operator()(SkScalar x, SkScalar y) const {
return fA * x + fB * y + fC;
}
bool twoPts(SkPoint pts[2]) const {
if (fB) {
pts[0] = { 0, -fC / fB };
pts[1] = { 1, (-fC - fA) / fB };
} else if (fA) {
pts[0] = { -fC / fA, 0 };
pts[1] = { (-fC - fB) / fA, 1 };
} else {
return false;
}
return true;
}
};
#include "src/core/SkEdgeClipper.h"
static SkPath clip(const SkPath& path, SkPoint p0, SkPoint p1) {
SkMatrix mx, inv;
SkVector v = p1 - p0;
mx.setAll(v.fX, -v.fY, p0.fX,
v.fY, v.fX, p0.fY,
0, 0, 1);
SkAssertResult(mx.invert(&inv));
SkPath rotated;
path.transform(inv, &rotated);
SkScalar big = 1e28f;
SkRect clip = {-big, 0, big, big };
struct Rec {
SkPath fResult;
SkPoint fPrev;
} rec;
SkEdgeClipper::ClipPath(rotated, clip, false,
[](SkEdgeClipper* clipper, bool newCtr, void* ctx) {
Rec* rec = (Rec*)ctx;
bool addLineTo = false;
SkPoint pts[4];
SkPath::Verb verb;
while ((verb = clipper->next(pts)) != SkPath::kDone_Verb) {
if (newCtr) {
rec->fResult.moveTo(pts[0]);
rec->fPrev = pts[0];
newCtr = false;
}
if (addLineTo || pts[0] != rec->fPrev) {
rec->fResult.lineTo(pts[0]);
}
switch (verb) {
case SkPath::kLine_Verb:
rec->fResult.lineTo (pts[1]);
rec->fPrev = pts[1];
break;
case SkPath::kQuad_Verb:
rec->fResult.quadTo(pts[1], pts[2]);
rec->fPrev = pts[2];
break;
case SkPath::kCubic_Verb:
rec->fResult.cubicTo(pts[1], pts[2], pts[3]);
rec->fPrev = pts[3];
break;
default: break;
}
addLineTo = true;
}
}, &rec);
rec.fResult.transform(mx);
return rec.fResult;
}
static SkPath clip(const SkPath& path, const SkHalfPlane& plane) {
SkPoint pts[2];
if (plane.twoPts(pts)) {
return clip(path, pts[0], pts[1]);
} else {
return SkPath();
}
}
static void draw_halfplane(SkCanvas* canvas, SkPoint p0, SkPoint p1, SkColor c) {
SkVector v = p1 - p0;
p0 = p0 - v * 1000;
p1 = p1 + v * 1000;
SkPaint paint;
paint.setColor(c);
canvas->drawLine(p0, p1, paint);
}
static SkPath make_path() {
SkRandom rand;
auto rand_pt = [&rand]() { return SkPoint{rand.nextF() * 400, rand.nextF() * 400}; };
SkPath path;
for (int i = 0; i < 4; ++i) {
path.moveTo(rand_pt()).quadTo(rand_pt(), rand_pt())
.quadTo(rand_pt(), rand_pt()).lineTo(rand_pt());
}
return path;
}
class HalfPlaneView : public Sample {
SkPoint fPts[2];
SkPath fPath;
SkString name() override { return SkString("halfplane"); }
void onOnceBeforeDraw() override {
fPts[0] = {0, 0};
fPts[1] = {3, 2};
fPath = make_path();
}
void onDrawContent(SkCanvas* canvas) override {
SkPaint paint;
paint.setColor({0.5f, 0.5f, 0.5f, 1.0f}, nullptr);
canvas->drawPath(fPath, paint);
paint.setColor({0, 0, 0, 1}, nullptr);
canvas->drawPath(clip(fPath, fPts[0], fPts[1]), paint);
draw_halfplane(canvas, fPts[0], fPts[1], SK_ColorRED);
}
Click* onFindClickHandler(SkScalar x, SkScalar y, skui::ModifierKey modi) override {
return new Click;
}
bool onClick(Click* click) override {
fPts[0] = click->fCurr;
fPts[1] = fPts[0] + SkPoint{3, 2};
return true;
}
};
DEF_SAMPLE( return new HalfPlaneView(); )
static void draw_halfplane(SkCanvas* canvas, const SkHalfPlane& p, SkColor c) {
SkPoint pts[2];
p.twoPts(pts);
draw_halfplane(canvas, pts[0], pts[1], c);
}
static void compute_half_planes(const SkMatrix& mx, SkScalar W, SkScalar H,
SkHalfPlane planes[4]) {
SkScalar a = mx[0], b = mx[1], c = mx[2],
d = mx[3], e = mx[4], f = mx[5],
g = mx[6], h = mx[7], i = mx[8];
planes[0] = { 2*g - 2*a/W, 2*h - 2*b/W, 2*i - 2*c/W };
planes[1] = { 2*a/W, 2*b/W, 2*c/W };
planes[2] = { 2*g - 2*d/H, 2*h - 2*e/H, 2*i - 2*f/H };
planes[3] = { 2*d/H, 2*e/H, 2*f/H };
}
class HalfPlaneView2 : public Sample {
SkPoint fPts[4];
SkPath fPath;
SkString name() override { return SkString("halfplane2"); }
void onOnceBeforeDraw() override {
fPath = make_path();
SkRect r = fPath.getBounds();
r.toQuad(fPts);
}
void onDrawContent(SkCanvas* canvas) override {
SkMatrix mx;
{
SkRect r = fPath.getBounds();
SkPoint src[4];
r.toQuad(src);
mx.setPolyToPoly(src, fPts, 4);
}
SkPaint paint;
canvas->drawPath(fPath, paint);
canvas->save();
canvas->concat(mx);
paint.setColor(0x40FF0000);
canvas->drawPath(fPath, paint);
canvas->restore();
// draw the frame
paint.setStrokeWidth(10);
paint.setColor(SK_ColorGREEN);
canvas->drawPoints(SkCanvas::kPoints_PointMode, 4, fPts, paint);
// draw the half-planes
SkHalfPlane planes[4];
compute_half_planes(mx, 400, 400, planes);
for (auto& p : planes) {
draw_halfplane(canvas, p, SK_ColorRED);
}
}
Click* onFindClickHandler(SkScalar x, SkScalar y, skui::ModifierKey modi) override {
SkScalar r = 8;
SkRect rect = SkRect::MakeXYWH(x - r, y - r, 2*r, 2*r);
for (int i = 0; i < 4; ++i) {
if (rect.contains(fPts[i].fX, fPts[i].fY)) {
Click* c = new Click;
c->fMeta.setS32("index", i);
return c;
}
}
return nullptr;
}
bool onClick(Click* click) override {
int32_t index;
SkAssertResult(click->fMeta.findS32("index", &index));
SkASSERT(index >= 0 && index < 4);
fPts[index] = click->fCurr;
return true;
}
};
DEF_SAMPLE( return new HalfPlaneView2(); )
#include "include/core/SkMatrix44.h"
#include "include/utils/Sk3D.h"
#include "tools/Resources.h"
static SkMatrix44 inv(const SkMatrix44& m) {
SkMatrix44 inverse;
SkAssertResult(m.invert(&inverse));
return inverse;
}
static void half_planes(const SkMatrix44& m44, SkScalar W, SkScalar H, SkHalfPlane planes[6]) {
float mx[16];
m44.asColMajorf(mx);
SkScalar a = mx[0], b = mx[4], /* c = mx[ 8], */ d = mx[12],
e = mx[1], f = mx[5], /* g = mx[ 9], */ h = mx[13],
i = mx[2], j = mx[6], /* k = mx[10], */ l = mx[14],
m = mx[3], n = mx[7], /* o = mx[11], */ p = mx[15];
a = 2*a/W - m; b = 2*b/W - n; d = 2*d/W - p;
e = 2*e/H - m; f = 2*f/H - n; h = 2*h/H - p;
i = 2*i - m; j = 2*j - n; l = 2*l - p;
planes[0] = { m - a, n - b, p - d }; // w - x
planes[1] = { m + a, n + b, p + d }; // w + x
planes[2] = { m - e, n - f, p - h }; // w - y
planes[3] = { m + e, n + f, p + h }; // w + y
planes[4] = { m - i, n - j, p - l }; // w - z
planes[5] = { m + i, n + j, p + l }; // w + z
}
class HalfPlaneView3 : public Sample {
float fNear = 0.05f;
float fFar = 4;
float fAngle = SK_ScalarPI / 4;
SkPoint3 fEye { 0, 0, 1.0f/tan(fAngle/2) - 1 };
SkPoint3 fCOA { 0, 0, 0 };
SkPoint3 fUp { 0, 1, 0 };
SkMatrix44 fRot;
SkPath fPath;
sk_sp<SkShader> fShader;
SkString name() override { return SkString("halfplane3"); }
void onOnceBeforeDraw() override {
fPath = make_path();
fShader = GetResourceAsImage("images/mandrill_128.png")
->makeShader(SkMatrix::MakeScale(3, 3));
}
void rotate(float x, float y, float z) {
SkMatrix44 r;
if (x) {
r.setRotateAboutUnit(1, 0, 0, x);
} else if (y) {
r.setRotateAboutUnit(0, 1, 0, y);
} else {
r.setRotateAboutUnit(0, 0, 1, z);
}
fRot.postConcat(r);
}
SkMatrix44 get44() const {
SkMatrix44 camera,
perspective,
viewport;
Sk3Perspective(&perspective, fNear, fFar, fAngle);
Sk3LookAt(&camera, fEye, fCOA, fUp);
viewport.setScale(200, 200, 1).postTranslate( 200, 200, 0);
return viewport * perspective * camera * fRot * inv(viewport);
}
void onDrawContent(SkCanvas* canvas) override {
SkMatrix44 mx44 = this->get44();
SkMatrix mx = mx44;
SkPaint paint;
paint.setColor({0.75, 0.75, 0.75, 1});
canvas->drawPath(fPath, paint);
paint.setShader(fShader);
canvas->save();
canvas->concat(mx);
paint.setAlphaf(0.33f);
canvas->drawPath(fPath, paint);
paint.setAlphaf(1.f);
canvas->restore();
SkHalfPlane planes[6];
half_planes(mx44, 400, 400, planes);
SkPath path = clip(fPath, planes[4]);
canvas->save();
canvas->concat(mx);
canvas->drawPath(path, paint);
canvas->restore();
// for (auto& p : planes) {
// draw_halfplane(canvas, p, SK_ColorRED);
// }
draw_halfplane(canvas, planes[4], SK_ColorBLUE);
draw_halfplane(canvas, planes[5], SK_ColorGREEN);
}
bool onChar(SkUnichar uni) override {
float delta = SK_ScalarPI / 30;
switch (uni) {
case '8': this->rotate( delta, 0, 0); return true;
case '2': this->rotate(-delta, 0, 0); return true;
case '4': this->rotate(0, delta, 0); return true;
case '6': this->rotate(0, -delta, 0); return true;
case '-': this->rotate(0, 0, delta); return true;
case '+': this->rotate(0, 0, -delta); return true;
case 'i': fEye.fZ += 0.1f; SkDebugf("ez %g\n", fEye.fZ); return true;
case 'k': fEye.fZ -= 0.1f; SkDebugf("ez %g\n", fEye.fZ); return true;
case 'n': fNear += 0.1f; SkDebugf("near %g\n", fNear); return true;
case 'N': fNear -= 0.1f; SkDebugf("near %g\n", fNear); return true;
case 'f': fFar += 0.1f; SkDebugf("far %g\n", fFar); return true;
case 'F': fFar -= 0.1f; SkDebugf("far %g\n", fFar); return true;
default: break;
}
return false;
}
Click* onFindClickHandler(SkScalar x, SkScalar y, skui::ModifierKey modi) override {
return nullptr;
}
bool onClick(Click* click) override {
return false;
}
};
DEF_SAMPLE( return new HalfPlaneView3(); )
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