submodule/skia/gm/mixercolorfilter.cpp

   1 /*
   2  * Copyright 2019 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/gm.h"
   9 #include "include/core/SkCanvas.h"
  10 #include "include/core/SkColor.h"
  11 #include "include/core/SkColorFilter.h"
  12 #include "include/core/SkImage.h"
  13 #include "include/core/SkMatrix.h"
  14 #include "include/core/SkPaint.h"
  15 #include "include/core/SkPoint.h"
  16 #include "include/core/SkRect.h"
  17 #include "include/core/SkRefCnt.h"
  18 #include "include/core/SkScalar.h"
  19 #include "include/core/SkShader.h"
  20 #include "include/core/SkSize.h"
  21 #include "include/core/SkString.h"
  22 #include "include/core/SkTileMode.h"
  23 #include "include/core/SkTypes.h"
  24 #include "include/effects/SkGradientShader.h"
  25 #include "include/effects/SkLumaColorFilter.h"
  26 #include "tools/Resources.h"
  27
  28 #include <math.h>
  29
  30 // A tint filter maps colors to a given range (gradient), based on the input luminance:
  31 //
  32 //   c' = lerp(lo, hi, luma(c))
  33 //
  34 // TODO: move to public headers/API?
  35 //
  36 static sk_sp<SkColorFilter> MakeTintColorFilter(SkColor lo, SkColor hi) {
  37     const auto r_lo = SkColorGetR(lo),
  38     g_lo = SkColorGetG(lo),
  39     b_lo = SkColorGetB(lo),
  40     a_lo = SkColorGetA(lo),
  41     r_hi = SkColorGetR(hi),
  42     g_hi = SkColorGetG(hi),
  43     b_hi = SkColorGetB(hi),
  44     a_hi = SkColorGetA(hi);
  45
  46     // We map component-wise:
  47     //
  48     //   r' = lo.r + (hi.r - lo.r) * luma
  49     //   g' = lo.g + (hi.g - lo.g) * luma
  50     //   b' = lo.b + (hi.b - lo.b) * luma
  51     //   a' = lo.a + (hi.a - lo.a) * luma
  52     //
  53     // The input luminance is stored in the alpha channel
  54     // (and RGB are cleared -- see SkLumaColorFilter). Thus:
  55     const float tint_matrix[] = {
  56         0, 0, 0, (r_hi - r_lo) / 255.0f, SkIntToScalar(r_lo) / 255.0f,
  57         0, 0, 0, (g_hi - g_lo) / 255.0f, SkIntToScalar(g_lo) / 255.0f,
  58         0, 0, 0, (b_hi - b_lo) / 255.0f, SkIntToScalar(b_lo) / 255.0f,
  59         0, 0, 0, (a_hi - a_lo) / 255.0f, SkIntToScalar(a_lo) / 255.0f,
  60     };
  61
  62     return SkColorFilters::Matrix(tint_matrix)->makeComposed(SkLumaColorFilter::Make());
  63 }
  64
  65 namespace {
  66
  67 class MixerCFGM final : public skiagm::GM {
  68 public:
  69     MixerCFGM(const SkSize& tileSize, size_t tileCount)
  70         : fTileSize(tileSize)
  71         , fTileCount(tileCount) {}
  72
  73 protected:
  74     SkString onShortName() override {
  75         return SkString("mixerCF");
  76     }
  77
  78     SkISize onISize() override {
  79         return SkISize::Make(fTileSize.width()  * 1.2f * fTileCount,
  80                              fTileSize.height() * 1.2f * 3);         // 3 rows
  81     }
  82
  83     void onDraw(SkCanvas* canvas) override {
  84         SkPaint paint;
  85
  86         const SkColor gradient_colors[] = { SK_ColorRED, SK_ColorGREEN, SK_ColorBLUE, SK_ColorRED };
  87         paint.setShader(SkGradientShader::MakeSweep(fTileSize.width()  / 2,
  88                                                     fTileSize.height() / 2,
  89                                                     gradient_colors, nullptr,
  90                                                     SK_ARRAY_COUNT(gradient_colors)));
  91
  92         auto cf0 = MakeTintColorFilter(0xff300000, 0xffa00000);  // red tint
  93         auto cf1 = MakeTintColorFilter(0xff003000, 0xff00a000);  // green tint
  94
  95         this->mixRow(canvas, paint, nullptr,     cf1);
  96         this->mixRow(canvas, paint,     cf0, nullptr);
  97         this->mixRow(canvas, paint,     cf0,     cf1);
  98     }
  99
 100 private:
 101     const SkSize fTileSize;
 102     const size_t fTileCount;
 103
 104     void mixRow(SkCanvas* canvas, SkPaint& paint,
 105                 sk_sp<SkColorFilter> cf0, sk_sp<SkColorFilter> cf1) {
 106         // We cycle through paint colors on each row, to test how the paint color flows through
 107         // the color-filter network
 108         const SkColor4f paintColors[] = {
 109             { 1.0f, 1.0f, 1.0f, 1.0f },  // Opaque white
 110             { 1.0f, 1.0f, 1.0f, 0.5f },  // Translucent white
 111             { 0.5f, 0.5f, 1.0f, 1.0f },  // Opaque pale blue
 112             { 0.5f, 0.5f, 1.0f, 0.5f },  // Translucent pale blue
 113         };
 114
 115         canvas->translate(0, fTileSize.height() * 0.1f);
 116         {
 117             SkAutoCanvasRestore arc(canvas, true);
 118             for (size_t i = 0; i < fTileCount; ++i) {
 119                 paint.setColor4f(paintColors[i % SK_ARRAY_COUNT(paintColors)]);
 120                 float t = static_cast<float>(i) / (fTileCount - 1);
 121                 paint.setColorFilter(SkColorFilters::Lerp(t, cf0, cf1));
 122                 canvas->translate(fTileSize.width() * 0.1f, 0);
 123                 canvas->drawRect(SkRect::MakeWH(fTileSize.width(), fTileSize.height()), paint);
 124                 canvas->translate(fTileSize.width() * 1.1f, 0);
 125             }
 126         }
 127         canvas->translate(0, fTileSize.height() * 1.1f);
 128     }
 129
 130     using INHERITED = skiagm::GM;
 131 };
 132
 133 } // namespace
 134
 135 DEF_GM( return new MixerCFGM(SkSize::Make(200, 250), 5); )