Name common cubic resamplers

Useful in client code to document what we're doing as we switch away
from SkFilterQuality.

Change-Id: I05737beb99a567a46a3c3ec418b7f7da71b1ff62
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/366723
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Florin Malita <fmalita@chromium.org>
Commit-Queue: Mike Reed <reed@google.com>

gm/anisotropic.cpp

@@ -22,7 +22,7 @@ namespace skiagm {
 // This GM exercises HighQuality anisotropic filtering.
 class AnisotropicGM : public GM {
 public:
-    AnisotropicGM() : fSampling({1.0f/3, 1.0f/3}) {
+    AnisotropicGM() : fSampling(SkCubicResampler::Mitchell()) {
         this->setBGColor(0xFFCCCCCC);
     }
 

gm/bicubic.cpp

@@ -34,8 +34,8 @@ DEF_SIMPLE_GM(bicubic, canvas, 300, 320) {
     SkPaint paint;
 
     SkImage::CubicResampler cubics[] = {
-        {      0, 1.0f/2 },
+        SkCubicResampler::CatmullRom(),
-        { 1.0f/3, 1.0f/3 },
+        SkCubicResampler::Mitchell(),
     };
     for (auto c : cubics) {
         paint.setShader(img->makeShader(SkTileMode::kClamp, SkTileMode::kClamp,

gm/bleed.cpp

@@ -246,7 +246,7 @@ protected:
 
         const SkSamplingOptions none(SkFilterMode::kNearest);
         const SkSamplingOptions  low(SkFilterMode::kLinear);
-        const SkSamplingOptions high({1.0f/3, 1.0f/3});
+        const SkSamplingOptions high(SkCubicResampler::Mitchell());
 
         SkScalar maxX = 0;
         for (bool antiAlias : {false, true}) {

gm/clippedbitmapshaders.cpp

@@ -92,7 +92,7 @@ protected:
         s.postTranslate(SLIDE_SIZE / 2, SLIDE_SIZE / 2);
         SkPaint paint;
         paint.setShader(bmp.makeShader(fMode, fMode,
-                                       fHQ ? SkSamplingOptions({1.0f/3, 1.0f/3})
+                                       fHQ ? SkSamplingOptions(SkCubicResampler::Mitchell())
                                            : SkSamplingOptions(),
                                        s));
 

gm/compressed_textures.cpp

@@ -270,7 +270,7 @@ private:
         int numMipLevels = SkMipmap::ComputeLevelCount(levelDimensions.width(),
                                                        levelDimensions.height()) + 1;
 
-        SkSamplingOptions sampling({1.0f/3, 1.0f/3});
+        SkSamplingOptions sampling(SkCubicResampler::Mitchell());
 
         bool isCompressed = false;
         if (image->isTextureBacked()) {

gm/constcolorprocessor.cpp

@@ -110,7 +110,7 @@ protected:
                 // Create a base-layer FP for the const color processor to draw on top of.
                 std::unique_ptr<GrFragmentProcessor> baseFP;
                 if (paintType >= SK_ARRAY_COUNT(kPaintColors)) {
-                    SkSamplingOptions high({1.0f/3, 1.0f/3});
+                    SkSamplingOptions high(SkCubicResampler::Mitchell());
                     GrColorInfo colorInfo;
                     GrFPArgs args(context, SkSimpleMatrixProvider(SkMatrix::I()), high, &colorInfo);
                     baseFP = as_SB(fShader)->asFragmentProcessor(args);

gm/filterbug.cpp

@@ -59,7 +59,7 @@ protected:
     }
 
     void onDraw(SkCanvas* canvas) override {
-        static const SkSamplingOptions kSampling({1.0f/3, 1.0f/3});
+        static const SkSamplingOptions kSampling(SkCubicResampler::Mitchell());
         static const bool kDoAA = true;
 
         {

gm/filterindiabox.cpp

@@ -41,7 +41,7 @@ static void draw_row(SkCanvas* canvas, const SkBitmap& bm, const SkMatrix& mat,
     draw_cell(canvas, bm, mat, 1 * dx, SkSamplingOptions(SkFilterMode::kLinear));
     draw_cell(canvas, bm, mat, 2 * dx, SkSamplingOptions(SkFilterMode::kLinear,
                                                          SkMipmapMode::kLinear));
-    draw_cell(canvas, bm, mat, 3 * dx, SkSamplingOptions({1.0f/3, 1.0f/3}));
+    draw_cell(canvas, bm, mat, 3 * dx, SkSamplingOptions(SkCubicResampler::Mitchell()));
 }
 
 class FilterIndiaBoxGM : public skiagm::GM {

gm/imagefiltersbase.cpp

@@ -190,7 +190,7 @@ static void draw_atlas(SkCanvas* canvas, SkImage* atlas, const SkRect& r,
     SkPaint paint;
     paint.setImageFilter(std::move(imf));
     paint.setAntiAlias(true);
-    SkSamplingOptions sampling({1.0f/3, 1.0f/3});
+    SkSamplingOptions sampling(SkCubicResampler::Mitchell());
     canvas->drawAtlas(atlas, &xform, &r, /*colors=*/nullptr, /*count=*/1, SkBlendMode::kSrc,
                       sampling, /*cullRect=*/nullptr, &paint);
 }

gm/imagefromyuvtextures.cpp

@@ -243,7 +243,7 @@ protected:
                     SkSamplingOptions(SkFilterMode::kNearest),
                     SkSamplingOptions(SkFilterMode::kLinear),
                     SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kNearest),
-                    SkSamplingOptions({1.0f/3, 1.0f/3})})
+                    SkSamplingOptions(SkCubicResampler::Mitchell())})
                 {
                     canvas->save();
                         canvas->scale(scale, scale);

gm/imagescalealigned.cpp

@@ -111,7 +111,7 @@ private:
             SkSamplingOptions(SkFilterMode::kNearest),
             SkSamplingOptions(SkFilterMode::kLinear),
             SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kLinear),
-            SkSamplingOptions({1.0f/3, 1.0f/3}),
+            SkSamplingOptions(SkCubicResampler::Mitchell()),
         };
         const bool AAs[] = { false, true };
 

gm/localmatriximageshader.cpp

@@ -71,7 +71,8 @@ DEF_SIMPLE_GM(localmatriximageshader_filtering, canvas, 256, 256) {
     auto image = GetResourceAsImage("images/mandrill_256.png");
     SkPaint p;
     SkMatrix m = SkMatrix::Scale(2, 2);
-    p.setShader(image->makeShader(SkSamplingOptions({1.0f/3, 1.0f/3}))->makeWithLocalMatrix(m));
+    p.setShader(image->makeShader(SkSamplingOptions(SkCubicResampler::Mitchell()))
+                ->makeWithLocalMatrix(m));
 
     canvas->drawRect(SkRect::MakeXYWH(0, 0, 256, 256), p);
 }

gm/mipmap.cpp

@@ -49,7 +49,7 @@ DEF_SIMPLE_GM(mipmap, canvas, 400, 200) {
         SkSamplingOptions(SkFilterMode::kNearest),
         SkSamplingOptions(SkFilterMode::kLinear),
         SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kLinear),
-        SkSamplingOptions({1.0f/3, 1.0f/3}),
+        SkSamplingOptions(SkCubicResampler::Mitchell()),
     };
 
     canvas->translate(20, 20);

gm/perspimages.cpp

@@ -82,7 +82,7 @@ protected:
                         SkSamplingOptions(SkFilterMode::kNearest),
                         SkSamplingOptions(SkFilterMode::kLinear),
                         SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kLinear),
-                        SkSamplingOptions({1.0f/3, 1.0f/3})}) {
+                        SkSamplingOptions(SkCubicResampler::Mitchell())}) {
                         for (const auto& img : fImages) {
                             canvas->save();
                             canvas->concat(m);

gm/perspshaders.cpp

@@ -157,7 +157,7 @@ protected:
         this->drawRow(canvas, SkSamplingOptions(SkFilterMode::kLinear,
                                                 SkMipmapMode::kNearest));
         canvas->translate(0, SkIntToScalar(kCellSize));
-        this->drawRow(canvas, SkSamplingOptions({1.0f/3, 1.0f/3}));
+        this->drawRow(canvas, SkSamplingOptions(SkCubicResampler::Mitchell()));
         canvas->translate(0, SkIntToScalar(kCellSize));
     }
 private:

gm/rectangletexture.cpp

@@ -157,7 +157,7 @@ private:
             SkSamplingOptions(SkFilterMode::kNearest),
             SkSamplingOptions(SkFilterMode::kLinear),
             SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kLinear),
-            SkSamplingOptions({1.0f/3, 1.0f/3}),
+            SkSamplingOptions(SkCubicResampler::Mitchell()),
         };
 
         constexpr SkScalar kScales[] = {1.0f, 1.2f, 0.75f};

gm/resizeimagefilter.cpp

@@ -77,7 +77,7 @@ protected:
             SkSamplingOptions(),
             SkSamplingOptions(SkFilterMode::kLinear),
             SkSamplingOptions(SkFilterMode::kLinear, SkMipmapMode::kLinear),
-            SkSamplingOptions({1.0f/3, 1.0f/3}),
+            SkSamplingOptions(SkCubicResampler::Mitchell()),
         };
         const SkRect srcRect = SkRect::MakeWH(96, 96);
         const SkSize deviceSize = SkSize::Make(16, 16);

gm/sample_matrix_constant.cpp

@@ -98,7 +98,8 @@ DEF_SIMPLE_GPU_GM(sample_matrix_constant, ctx, rtCtx, canvas, 1024, 256) {
         SkMatrix matrix;
         SkSimpleMatrixProvider matrixProvider(matrix);
         GrColorInfo colorInfo;
-        GrFPArgs args(ctx, matrixProvider, SkSamplingOptions({1.0f/3, 1.0f/3}), &colorInfo);
+        GrFPArgs args(ctx, matrixProvider, SkSamplingOptions(SkCubicResampler::Mitchell()),
+                      &colorInfo);
         std::unique_ptr<GrFragmentProcessor> gradientFP = as_SB(shader)->asFragmentProcessor(args);
         draw(std::move(gradientFP), 512, 0);
         gradientFP = as_SB(shader)->asFragmentProcessor(args);

gm/sample_matrix_variable.cpp

@@ -96,7 +96,8 @@ DEF_SIMPLE_GPU_GM(sample_matrix_variable, ctx, rtCtx, canvas, 512, 256) {
         SkMatrix matrix;
         SkSimpleMatrixProvider matrixProvider(matrix);
         GrColorInfo colorInfo;
-        GrFPArgs args(ctx, matrixProvider, SkSamplingOptions({1.0f/3, 1.0f/3}), &colorInfo);
+        GrFPArgs args(ctx, matrixProvider, SkSamplingOptions(SkCubicResampler::Mitchell()),
+                      &colorInfo);
         std::unique_ptr<GrFragmentProcessor> gradientFP = as_SB(shader)->asFragmentProcessor(args);
         draw(std::move(gradientFP), -128, 256, 256, 0);
     }

gm/tiledscaledbitmap.cpp

@@ -66,7 +66,7 @@ protected:
         mat.postTranslate(-72, -72);
 
         paint.setShader(fBitmap.makeShader(SkTileMode::kRepeat, SkTileMode::kRepeat,
-                                           SkSamplingOptions({1.0f/3, 1.0f/3}), mat));
+                                           SkSamplingOptions(SkCubicResampler::Mitchell()), mat));
         canvas->drawRect({ 8, 8, 1008, 608 }, paint);
     }
 

include/core/SkSamplingOptions.h

@@ -45,6 +45,10 @@ enum class SkMipmapMode {
  */
 struct SkCubicResampler {
     float B, C;
+
+    // Historic default for kHigh_SkFilterQuality
+    static constexpr SkCubicResampler Mitchell() { return {1/3.0f, 1/3.0f}; }
+    static constexpr SkCubicResampler CatmullRom() { return {0.0f, 1/2.0f}; }
 };
 
 struct SK_API SkSamplingOptions {