megalooper.cpp revision faba3715b8ddfaa0ce4df79bc8006e9bc7694e5b 
1/*
2 * Copyright 2013 Google Inc.
3 *
4 * Use of this source code is governed by a BSD-style license that can be
5 * found in the LICENSE file.
6 */
7
8#include "gm.h"
9#include "SkBlurMask.h"
10#include "SkBlurMaskFilter.h"
11#include "SkCanvas.h"
12#include "SkColorFilter.h"
13#include "SkLayerDrawLooper.h"
14
15// This GM tests 3 different ways of drawing four shadows around a square:
16//      just using 4 blurred rects
17//      using 4 1-level draw loopers
18//      using 1 4-level draw looper
19// They all produce exactly the same pixels
20class MegaLooperGM : public skiagm::GM {
21public:
22    // The types define "<# of loopers> x <# of stages per looper>"
23    enum Type {
24        k0x0_Type,  // draw without loopers at all
25        k4x1_Type,  // a looper for each shadow
26        k1x4_Type,  // all four shadows in one looper
27    };
28
29    MegaLooperGM(Type type) : fType(type) {}
30
31protected:
32    virtual SkString onShortName() {
33        switch (fType) {
34        case k0x0_Type:
35            return SkString("megalooper_0x0");
36            break;
37        case k4x1_Type:
38            return SkString("megalooper_4x1");
39            break;
40        case k1x4_Type:     // fall through
41        default:
42            return SkString("megalooper_1x4");
43            break;
44        }
45    }
46
47    virtual SkISize onISize() {
48        return SkISize::Make(kWidth, kHeight);
49    }
50
51    virtual void onDraw(SkCanvas* canvas) {
52        for (int y = 100; y < kHeight; y += 200) {
53            for (int x = 100; x < kWidth; x += 200) {
54                switch (fType) {
55                    case k0x0_Type:
56                        draw0x0(canvas, SkIntToScalar(x), SkIntToScalar(y));
57                        break;
58                    case k4x1_Type:
59                        draw4x1(canvas, SkIntToScalar(x), SkIntToScalar(y));
60                        break;
61                    case k1x4_Type:     // fall through
62                    default:
63                        draw1x4(canvas, SkIntToScalar(x), SkIntToScalar(y));
64                        break;
65                }
66            }
67        }
68    }
69
70private:
71    static constexpr int kWidth = 800;
72    static constexpr int kHeight = 800;
73    static constexpr int kHalfOuterClipSize = 100;
74    static constexpr int kHalfSquareSize = 50;
75    static constexpr int kOffsetToOutsideClip = kHalfSquareSize + kHalfOuterClipSize + 1;
76
77    static const SkPoint gBlurOffsets[4];
78    static const SkColor gColors[4];
79    Type fType;
80
81    // Just draw a blurred rect at each of the four corners of a square (centered at x,y).
82    // Use two clips to define a rectori where we want pixels to appear.
83    void draw0x0(SkCanvas* canvas, SkScalar x, SkScalar y) {
84        SkRect innerClip = { -kHalfSquareSize, -kHalfSquareSize, kHalfSquareSize, kHalfSquareSize };
85        innerClip.offset(x, y);
86
87        SkRect outerClip = {
88            -kHalfOuterClipSize-kHalfSquareSize, -kHalfOuterClipSize-kHalfSquareSize,
89             kHalfOuterClipSize+kHalfSquareSize,  kHalfOuterClipSize+kHalfSquareSize
90        };
91        outerClip.offset(x, y);
92
93        canvas->save();
94        canvas->clipRect(outerClip, SkCanvas::kIntersect_Op);
95        canvas->clipRect(innerClip, SkCanvas::kDifference_Op);
96
97        SkPaint paint;
98        paint.setAntiAlias(true);
99        paint.setMaskFilter(MakeBlur());
100
101        for (int i = 0; i < 4; ++i) {
102            paint.setColor(gColors[i]);
103
104            SkRect rect = { -kHalfSquareSize, -kHalfSquareSize, kHalfSquareSize, kHalfSquareSize };
105            rect.offset(gBlurOffsets[i]);
106            rect.offset(x, y);
107            canvas->drawRect(rect, paint);
108        }
109
110        canvas->restore();
111    }
112
113    static sk_sp<SkMaskFilter> MakeBlur() {
114        const SkScalar kBlurSigma = SkBlurMask::ConvertRadiusToSigma(SkIntToScalar(25));
115
116        return SkBlurMaskFilter::Make(kNormal_SkBlurStyle, kBlurSigma,
117                                      SkBlurMaskFilter::kHighQuality_BlurFlag);
118    }
119
120    // This draws 4 blurred shadows around a single square (centered at x, y).
121    // Each blur is offset +/- half the square's side in x & y from the original
122    // (so each blurred rect is centered at one of the corners of the original).
123    // For each blur a large outer clip is centered around the blurred rect
124    // while a difference clip stays at the location of the original rect.
125    // Each blurred rect is drawn with a draw looper where the original (non-
126    // blurred rect) is offset to reside outside of the large outer clip (so
127    // it never appears) but the offset in the draw looper is used to translate
128    // the blurred version back into the clip.
129    void draw4x1(SkCanvas* canvas, SkScalar x, SkScalar y) {
130
131        for (int i = 0; i < 4; ++i) {
132            SkPaint loopPaint;
133
134            loopPaint.setLooper(create1Looper(-kOffsetToOutsideClip, 0, gColors[i]));
135            loopPaint.setAntiAlias(true);
136
137            SkRect outerClip = {
138                -kHalfOuterClipSize, -kHalfOuterClipSize,
139                kHalfOuterClipSize, kHalfOuterClipSize
140            };
141            outerClip.offset(x, y);
142            // center it on the blurred rect
143            outerClip.offset(gBlurOffsets[i]);
144
145            SkRect rect = { -kHalfSquareSize, -kHalfSquareSize, kHalfSquareSize, kHalfSquareSize };
146            rect.offset(x, y);
147
148            canvas->save();
149                canvas->clipRect(outerClip, SkCanvas::kIntersect_Op);
150                canvas->clipRect(rect, SkCanvas::kDifference_Op);
151
152                // move the rect to where we want the blur to appear
153                rect.offset(gBlurOffsets[i]);
154                // then move it outside the clip (the blur stage of the draw
155                // looper will undo this translation)
156                rect.offset(SkIntToScalar(kOffsetToOutsideClip), 0);
157
158                canvas->drawRect(rect, loopPaint);
159            canvas->restore();
160        }
161    }
162
163    // Create a 1-tier drawlooper
164    sk_sp<SkDrawLooper> create1Looper(SkScalar xOff, SkScalar yOff, SkColor color) {
165        SkLayerDrawLooper::Builder looperBuilder;
166        SkLayerDrawLooper::LayerInfo info;
167
168        info.fPaintBits = SkLayerDrawLooper::kColorFilter_Bit |
169                          SkLayerDrawLooper::kMaskFilter_Bit;
170        info.fColorMode = SkBlendMode::kSrc;
171        info.fOffset.set(xOff, yOff);
172        info.fPostTranslate = false;
173
174        SkPaint* paint = looperBuilder.addLayer(info);
175
176        paint->setMaskFilter(MakeBlur());
177
178        paint->setColorFilter(SkColorFilter::MakeModeFilter(color, SkBlendMode::kSrcIn));
179
180        return looperBuilder.detach();
181    }
182
183    void draw1x4(SkCanvas* canvas, SkScalar x, SkScalar y) {
184        SkRect rect = { -kHalfSquareSize, -kHalfSquareSize, kHalfSquareSize, kHalfSquareSize };
185        rect.offset(x, y);
186
187        SkRect outerClip = {
188            -kHalfOuterClipSize-kHalfSquareSize, -kHalfOuterClipSize-kHalfSquareSize,
189             kHalfOuterClipSize+kHalfSquareSize,  kHalfOuterClipSize+kHalfSquareSize
190        };
191        outerClip.offset(x, y);
192
193        SkPaint paint;
194        paint.setAntiAlias(true);
195        paint.setLooper(create4Looper(-kOffsetToOutsideClip-kHalfSquareSize, 0));
196
197        canvas->save();
198            canvas->clipRect(outerClip, SkCanvas::kIntersect_Op);
199            canvas->clipRect(rect, SkCanvas::kDifference_Op);
200
201            rect.offset(SkIntToScalar(kOffsetToOutsideClip+kHalfSquareSize), 0);
202            canvas->drawRect(rect, paint);
203        canvas->restore();
204    }
205
206    // Create a 4-tier draw looper
207    sk_sp<SkDrawLooper> create4Looper(SkScalar xOff, SkScalar yOff) {
208        SkLayerDrawLooper::Builder looperBuilder;
209        SkLayerDrawLooper::LayerInfo info;
210
211        info.fPaintBits = SkLayerDrawLooper::kColorFilter_Bit |
212                          SkLayerDrawLooper::kMaskFilter_Bit;
213        info.fColorMode = SkBlendMode::kSrc;
214        info.fPostTranslate = false;
215
216        SkPaint* paint;
217
218        for (int i = 3; i >= 0; --i) {
219            info.fOffset.set(xOff+gBlurOffsets[i].fX, yOff+gBlurOffsets[i].fY);
220            paint = looperBuilder.addLayer(info);
221
222            paint->setMaskFilter(MakeBlur());
223
224            paint->setColorFilter(SkColorFilter::MakeModeFilter(gColors[i], SkBlendMode::kSrcIn));
225        }
226
227        return looperBuilder.detach();
228    }
229
230    typedef GM INHERITED;
231};
232
233const SkPoint MegaLooperGM::gBlurOffsets[4] = {
234    {  kHalfSquareSize,  kHalfSquareSize },
235    { -kHalfSquareSize,  kHalfSquareSize },
236    {  kHalfSquareSize, -kHalfSquareSize },
237    { -kHalfSquareSize, -kHalfSquareSize }
238};
239
240const SkColor MegaLooperGM::gColors[4] = {
241    SK_ColorGREEN, SK_ColorYELLOW, SK_ColorBLUE, SK_ColorRED
242};
243
244DEF_GM( return new MegaLooperGM(MegaLooperGM::k0x0_Type); )
245DEF_GM( return new MegaLooperGM(MegaLooperGM::k4x1_Type); )
246DEF_GM( return new MegaLooperGM(MegaLooperGM::k1x4_Type); )
247