SkColorSpaceXformSteps

Lots TODO.

Change-Id: I95edb764b85a5140d432adb506c3b537869e6df4
Reviewed-on: https://skia-review.googlesource.com/129933
Commit-Queue: Mike Klein <mtklein@chromium.org>
Reviewed-by: Brian Osman <brianosman@google.com>
Auto-Submit: Mike Klein <mtklein@chromium.org>

1 files changed, 150 insertions, 0 deletions

diff --git a/tests/SkColorSpaceXformStepsTest.cpp b/tests/SkColorSpaceXformStepsTest.cpp
new file mode 100644
index 0000000000..47e5e1b90b
--- /dev/null
+++ b/tests/SkColorSpaceXformStepsTest.cpp
@@ -0,0 +1,150 @@
+/*
+ * 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 "SkColorSpacePriv.h"
+#include "SkColorSpaceXformSteps.h"
+#include "Test.h"
+
+template <typename T>
+static void check_eq(skiatest::Reporter* r, SkColorSpaceXformSteps steps, T baseline) {
+    REPORTER_ASSERT(r, steps.early_unpremul  == baseline.early_unpremul);
+    REPORTER_ASSERT(r, steps.linearize_src   == baseline.linearize_src);
+    REPORTER_ASSERT(r, steps.late_unpremul   == baseline.late_unpremul);
+    REPORTER_ASSERT(r, steps.gamut_transform == baseline.gamut_transform);
+    REPORTER_ASSERT(r, steps.early_encode    == baseline.early_encode);
+    REPORTER_ASSERT(r, steps.premul          == baseline.premul);
+    REPORTER_ASSERT(r, steps.linearize_dst   == baseline.linearize_dst);
+    REPORTER_ASSERT(r, steps.late_encode     == baseline.late_encode);
+
+    // A couple (redundant) sanity checks that cover impossible states.
+    // At most one of the early/late options should happen, possibly neither.
+    REPORTER_ASSERT(r, !(steps.early_unpremul && steps.late_unpremul));
+    REPORTER_ASSERT(r, !(steps.early_encode   && steps.late_encode));
+}
+
+DEF_TEST(SkColorSpaceXformSteps, r) {
+    auto srgb_L = SkColorSpace::MakeSRGB(),
+        adobe_L = SkColorSpace::MakeRGB(g2Dot2_TransferFn, SkColorSpace::kAdobeRGB_Gamut),
+       srgb22_L = SkColorSpace::MakeRGB(g2Dot2_TransferFn, SkColorSpace::    kSRGB_Gamut),
+         srgb_N =   srgb_L->makeNonlinearBlending(),
+        adobe_N =  adobe_L->makeNonlinearBlending(),
+       srgb22_N = srgb22_L->makeNonlinearBlending();
+
+    struct {
+        sk_sp<SkColorSpace> src, dst;
+
+        bool early_unpremul;
+        bool linearize_src;
+        bool late_unpremul;
+
+        bool gamut_transform;
+        bool early_encode;
+        bool premul;
+
+        bool linearize_dst;
+        bool late_encode;
+    } tests[] = {
+        // The first eight cases we test are back and forth between two color spaces with
+        // different gamuts and transfer functions.  There's not much optimization possible here.
+
+        { adobe_N, srgb_N,
+            true,   // src is encoded as f(s)*a,a, so we unpremul to f(s),a before linearizing.
+            true,   // Linearize to s,a.
+            false,
+
+            true,  // Gamut transform.
+            true,  // Non-linear blending, so we encode to sRGB g(s),a early.
+            true,  // Premul to g(s)*a,a
+
+            false,  // Non-linear blending, so no need to linearize dst.
+            false,  // Non-linear blending, so the output of our blend function is what we want.
+        },
+        { srgb_N, adobe_N,  true,true,false, true,true,true, false,false },
+
+        { adobe_L, srgb_L,
+            false,  // src is encoded as f(s*a),a, so we linearize before unpremul.
+            true,   // Linearize,
+            true,   // then unpremul.
+
+            true,   // Gamut transform.
+            false,  // We're doing linear blending, so we don't encode to sRGB yet.
+            true,   // Premul so we can blend.
+
+            true,   // We're doing linear blending, so we need to linearize dst.
+            true,   // Once blending is done, finally encode to sRGB.
+        },
+        { srgb_L, adobe_L, false,true,true, true,false,true, true,true },
+
+        { adobe_L, srgb_N,
+            false,  // src is encoded as f(s*a),a, so we linearize before unpremul.
+            true,   // Linearize,
+            true,   // then unpremul.
+
+            true,   // Gamut transform
+            true,   // We're doing non-linear blending, so encode to sRGB now.
+            true,   // (non-linear) premul
+
+            false,  // We're doing non-linear blending, so dst is already ready to blend.
+            false,  // The output of the blend is just what we want.
+        },
+        { srgb_L, adobe_N,  false,true,true, true,true,true, false,false },
+
+        { adobe_N, srgb_L,
+            true,   // src is encoded as f(s)*a,a, so we unpremul to f(s),a before linearizing.
+            true,   // Linearize to s,a.
+            false,
+
+            true,   // Gamut transform
+            false,  // We're doing linear blending, so we don't encode to sRGB yet.
+            true,   // (linear) premul
+
+            true,   // We're doing linear blending, so we need to linearize dst.
+            true,   // Once blending is done, finally encode to sRGB.
+        },
+        { srgb_N, adobe_L,  true,true,false, true,false,true, true,true },
+
+        // These eight cases transform between color spaces with different
+        // transfer functions and the same gamut.  Optimization here is limited
+        // to skipping the gamut_transform step: |
+        //                                       v This column of true can all become false.
+        { srgb_N, srgb22_N,   true,true,false, true,true,true,  false,false },
+        { srgb22_N, srgb_N,   true,true,false, true,true,true,  false,false },
+
+        { srgb_L, srgb22_L,   false,true,true, true,false,true, true,true   },
+        { srgb22_L, srgb_L,   false,true,true, true,false,true, true,true   },
+
+        { srgb_N, srgb22_L,   true,true,false, true,false,true, true,true   },
+        { srgb22_N, srgb_L,   true,true,false, true,false,true, true,true   },
+
+        { srgb_L, srgb22_N,   false,true,true, true,true,true,  false,false },
+        { srgb22_L, srgb_N,   false,true,true, true,true,true,  false,false },
+
+        // These four test cases test drawing in the same color space.
+        // There is lots of room for optimization here, but none implemented yet.
+        { srgb_N, srgb_N,   true,true,false, true,true,true,  false,false },  // a.k.a  legacy 8888
+        { srgb_L, srgb_L,   false,true,true, true,false,true, true,true   },  // <canvas> use case
+        { srgb_N, srgb_L,   true,true,false, true,false,true, true,true   },
+        { srgb_L, srgb_N,   false,true,true, true,true,true,  false,false },
+
+        // TODO: versions of above crossing in linear transfer functions
+    };
+
+    for (auto t : tests) {
+        // Our expectations are written for premul source alpha types.
+        check_eq(r, SkColorSpaceXformSteps(t.src.get(), kPremul_SkAlphaType, t.dst.get()), t);
+
+        // Opaque and unpremul sources should always go through the same steps,
+        // and they should be the same as premul's steps, with these fixed premul/unpremul steps.
+        auto upm = t;
+        upm.early_unpremul = false;
+        upm.late_unpremul  = false;
+        upm.premul         = true;
+
+        check_eq(r, SkColorSpaceXformSteps(t.src.get(), kUnpremul_SkAlphaType, t.dst.get()), upm);
+        check_eq(r, SkColorSpaceXformSteps(t.src.get(),   kOpaque_SkAlphaType, t.dst.get()), upm);
+    }
+}