Refactored SkColorSpace and added in a Lab PCS GM

src/core/SkColorSpace_XYZTRC.cpp

Index: src/core/SkColorSpace_XYZTRC.cpp
diff --git a/src/core/SkColorSpace_XYZTRC.cpp b/src/core/SkColorSpace_XYZTRC.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b77c9ff24e2067069754f16505f6089d2a94f505
--- /dev/null
+++ b/src/core/SkColorSpace_XYZTRC.cpp
@@ -0,0 +1,60 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkColorSpace_XYZTRC.h"
+
+static constexpr float gSRGB_toXYZD50[] {
+    0.4358f, 0.3853f, 0.1430f,    // Rx, Gx, Bx
+    0.2224f, 0.7170f, 0.0606f,    // Ry, Gy, Gz
+    0.0139f, 0.0971f, 0.7139f,    // Rz, Gz, Bz
+};
+
+SkColorSpace_XYZTRC::SkColorSpace_XYZTRC(SkGammaNamed gammaNamed, const SkMatrix44& toXYZD50)
+    : INHERITED(nullptr)
+    , fGammaNamed(gammaNamed)
+    , fGammas(nullptr)
+    , fToXYZD50(toXYZD50)
+    , fFromXYZD50(SkMatrix44::kUninitialized_Constructor)
+{}
+
+SkColorSpace_XYZTRC::SkColorSpace_XYZTRC(SkGammaNamed gammaNamed, sk_sp<SkGammas> gammas,
+                                         const SkMatrix44& toXYZD50, sk_sp<SkData> profileData)
+    : INHERITED(std::move(profileData))
+    , fGammaNamed(gammaNamed)
+    , fGammas(std::move(gammas))
+    , fToXYZD50(toXYZD50)
+    , fFromXYZD50(SkMatrix44::kUninitialized_Constructor)
+{}
+
+sk_sp<SkColorSpace> SkColorSpace_XYZTRC::makeLinearGammaImpl() {
+    if (this->gammaIsLinear()) {
+        return sk_ref_sp(this);
+    }
+    return SkColorSpace_Base::NewRGB(kLinear_SkGammaNamed, fToXYZD50);
+}
+
+bool SkColorSpace_XYZTRC::gammaCloseToSRGBImpl() const {
+    return kSRGB_SkGammaNamed == fGammaNamed || k2Dot2Curve_SkGammaNamed == fGammaNamed;
+}
+
+bool SkColorSpace_XYZTRC::gammaIsLinearImpl() const {
+    return kLinear_SkGammaNamed == fGammaNamed;
+}
+
+const SkMatrix44* SkColorSpace_XYZTRC::fromXYZD50() const {
+    fFromXYZOnce([this] {
+        if (!fToXYZD50.invert(&fFromXYZD50)) {
+            // If a client gives us a dst gamut with a transform that we can't invert, we will
+            // simply give them back a transform to sRGB gamut.
+            SkDEBUGFAIL("Non-invertible XYZ matrix, defaulting to sRGB");

[msarett, 2016/10/11 13:40:31]

Looking at this code, I kind of think we might want to adopt something similar
for makeLinearGamma()...  Returning nullptr when the client expects non-null
isn't very safe.

+            SkMatrix44 srgbToxyzD50(SkMatrix44::kUninitialized_Constructor);
+            srgbToxyzD50.set3x3RowMajorf(gSRGB_toXYZD50);
+            srgbToxyzD50.invert(&fFromXYZD50);
+        }
+    });
+    return &fFromXYZD50;
+}