Add SkDefaultXform as a catch-all to handle color conversions

tests/ColorSpaceXformTest.cpp

Index: tests/ColorSpaceXformTest.cpp
diff --git a/tests/ColorSpaceXformTest.cpp b/tests/ColorSpaceXformTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..220509b9f6390c165ff2885cc6e867f19ceaa3dc
--- /dev/null
+++ b/tests/ColorSpaceXformTest.cpp
@@ -0,0 +1,103 @@
+/*
+ * 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 "Resources.h"
+#include "SkCodec.h"
+#include "SkColorPriv.h"
+#include "SkColorSpace.h"
+#include "SkColorSpace_Base.h"
+#include "SkColorSpaceXform.h"
+#include "Test.h"
+
+class ColorSpaceXformTest {
+public:
+    static SkDefaultXform* CreateDefaultXform(const sk_sp<SkGammas>& srcGamma,
+            const SkMatrix44& srcToDst, const sk_sp<SkGammas>& dstGamma) {
+        return new SkDefaultXform(srcGamma, srcToDst, dstGamma);
+    }
+};
+
+static void test_xform(skiatest::Reporter* r, const sk_sp<SkGammas>& gammas) {
+    // Arbitrary set of 10 pixels
+    constexpr int width = 10;
+    constexpr uint32_t srcPixels[width] = {
+            0xFFABCDEF, 0xFF146829, 0xFF382759, 0xFF184968, 0xFFDE8271,
+            0xFF32AB52, 0xFF0383BC, 0xFF000000, 0xFFFFFFFF, 0xFFDDEEFF, };
+    uint32_t dstPixels[width];
+
+    // Identity matrix
+    SkMatrix44 srcToDst = SkMatrix44::I();
+
+    // Create and perform xform
+    std::unique_ptr<SkColorSpaceXform> xform(
+            ColorSpaceXformTest::CreateDefaultXform(gammas, srcToDst, gammas));
+    xform->xform_RGBA_8888(dstPixels, srcPixels, width);
+
+    // Since the matrix is the identity, and the gamma curves match, the pixels
+    // should be unchanged.
+    for (int i = 0; i < width; i++) {
+        // TODO (msarett):
+        // As the implementation changes, we may want to use a tolerance here.
+        REPORTER_ASSERT(r, ((srcPixels[i] >>  0) & 0xFF) == SkGetPackedR32(dstPixels[i]));
+        REPORTER_ASSERT(r, ((srcPixels[i] >>  8) & 0xFF) == SkGetPackedG32(dstPixels[i]));
+        REPORTER_ASSERT(r, ((srcPixels[i] >> 16) & 0xFF) == SkGetPackedB32(dstPixels[i]));
+        REPORTER_ASSERT(r, ((srcPixels[i] >> 24) & 0xFF) == SkGetPackedA32(dstPixels[i]));
+    }
+}
+
+DEF_TEST(ColorSpaceXform_TableGamma, r) {
+    // Lookup-table based gamma curves
+    SkGammaCurve red, green, blue;
+    constexpr size_t tableSize = 10;
+    red.fTable = std::unique_ptr<float[]>(new float[tableSize]);
+    green.fTable = std::unique_ptr<float[]>(new float[tableSize]);
+    blue.fTable = std::unique_ptr<float[]>(new float[tableSize]);
+    red.fTableSize = green.fTableSize = blue.fTableSize = 10;
+    red.fTable[0] = green.fTable[0] = blue.fTable[0] = 0.00f;
+    red.fTable[1] = green.fTable[1] = blue.fTable[1] = 0.05f;
+    red.fTable[2] = green.fTable[2] = blue.fTable[2] = 0.10f;
+    red.fTable[3] = green.fTable[3] = blue.fTable[3] = 0.15f;
+    red.fTable[4] = green.fTable[4] = blue.fTable[4] = 0.25f;
+    red.fTable[5] = green.fTable[5] = blue.fTable[5] = 0.35f;
+    red.fTable[6] = green.fTable[6] = blue.fTable[6] = 0.45f;
+    red.fTable[7] = green.fTable[7] = blue.fTable[7] = 0.60f;
+    red.fTable[8] = green.fTable[8] = blue.fTable[8] = 0.75f;
+    red.fTable[9] = green.fTable[9] = blue.fTable[9] = 1.00f;
+    sk_sp<SkGammas> gammas =
+            sk_make_sp<SkGammas>(std::move(red), std::move(green), std::move(blue));
+    test_xform(r, gammas);
+}
+
+DEF_TEST(ColorSpaceXform_ParametricGamma, r) {
+    // Parametric gamma curves
+    SkGammaCurve red, green, blue;
+
+    // Interval, switch xforms at 0.5f
+    red.fD = green.fD = blue.fD = 0.5f;
+
+    // First equation, Y = 0.5f * X
+    red.fE = green.fE = blue.fE = 0.5f;
+
+    // Second equation, Y = ((1.0f * X) + 0.0f) ^ 3.0f + 0.125f
+    // Note that the function is continuous:
+    // 0.5f * 0.5f = ((1.0f * 0.5f) + 0.0f) ^ 3.0f + 0.125f = 0.25f
+    red.fA = green.fA = blue.fA = 1.0f;
+    red.fB = green.fB = blue.fB = 0.0f;
+    red.fC = green.fC = blue.fC = 0.125f;
+    red.fG = green.fG = blue.fG = 3.0f;
+    sk_sp<SkGammas> gammas = sk_make_sp<SkGammas>(std::move(red), std::move(green), std::move(blue));
+    test_xform(r, gammas);
+}
+
+DEF_TEST(ColorSpaceXform_ExponentialGamma, r) {
+    // Exponential gamma curves
+    SkGammaCurve red, green, blue;
+    red.fValue = green.fValue = blue.fValue = 4.0f;
+    sk_sp<SkGammas> gammas =
+            sk_make_sp<SkGammas>(std::move(red), std::move(green), std::move(blue));
+    test_xform(r, gammas);
+}