experiment: float color components

tests/SkColor4fTest.cpp

Index: tests/SkColor4fTest.cpp
diff --git a/tests/SkColor4fTest.cpp b/tests/SkColor4fTest.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..b09b0c479a055907271bd753bec4737f061de5e6
--- /dev/null
+++ b/tests/SkColor4fTest.cpp
@@ -0,0 +1,62 @@
+/*
+ * 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 "SkColor.h"
+#include "SkShader.h"
+#include "SkColorMatrixFilter.h"
+#include "Test.h"
+#include "SkRandom.h"
+
+DEF_TEST(SkColor4f_FromColor, reporter) {
+    const struct {
+        SkColor     fC;
+        SkColor4f   fC4;
+    } recs[] = {
+        { SK_ColorBLACK, { 1, 0, 0, 0 } },
+        { SK_ColorWHITE, { 1, 1, 1, 1 } },
+        { SK_ColorRED,   { 1, 1, 0, 0 } },
+        { SK_ColorGREEN, { 1, 0, 1, 0 } },
+        { SK_ColorBLUE,  { 1, 0, 0, 1 } },
+        { 0,             { 0, 0, 0, 0 } },
+        { 0x55AAFF00,    { 1/3.0f, 2/3.0f, 1, 0 } },
+    };
+
+    for (const auto& r : recs) {
+        SkColor4f c4 = SkColor4f::FromColor(r.fC);
+        REPORTER_ASSERT(reporter, c4 == r.fC4);
+    }
+}
+
+static bool nearly_equal(float a, float b) {
+    const float kTolerance = 1.0f / (1 << 20);
+    return fabsf(a - b) < kTolerance;
+}
+
+DEF_TEST(SkColor4f_premul, reporter) {
+    SkRandom rand;
+
+    for (int i = 0; i < 1000000; ++i) {
+        // First just test opaque colors, so that the premul should be exact
+        SkColor4f c4 {
+            1, rand.nextUScalar1(), rand.nextUScalar1(), rand.nextUScalar1()
+        };
+        SkPM4f pm4 = c4.premul();
+        REPORTER_ASSERT(reporter, pm4.fVec[SK_A_INDEX] == c4.fA);
+        REPORTER_ASSERT(reporter, pm4.fVec[SK_R_INDEX] == c4.fA * c4.fR);
+        REPORTER_ASSERT(reporter, pm4.fVec[SK_G_INDEX] == c4.fA * c4.fG);
+        REPORTER_ASSERT(reporter, pm4.fVec[SK_B_INDEX] == c4.fA * c4.fB);
+
+        // We compare with a tolerance, in case our premul multiply is implemented at slightly
+        // different precision than the test code.
+        c4.fA = rand.nextUScalar1();
+        pm4 = c4.premul();
+        REPORTER_ASSERT(reporter, pm4.fVec[SK_A_INDEX] == c4.fA);
+        REPORTER_ASSERT(reporter, nearly_equal(pm4.fVec[SK_R_INDEX], c4.fA * c4.fR));
+        REPORTER_ASSERT(reporter, nearly_equal(pm4.fVec[SK_G_INDEX], c4.fA * c4.fG));
+        REPORTER_ASSERT(reporter, nearly_equal(pm4.fVec[SK_B_INDEX], c4.fA * c4.fB));
+    }
+}