Introduce SkGammas type to represent ICC gamma curves

tests/ColorSpaceTest.cpp

 /*
  * 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 "SkColorSpace.h"
@@ skipping 17 matching lines @@
         return;
     }
 
     SkAutoTDelete<SkCodec> codec(SkCodec::NewFromStream(stream.release()));
     REPORTER_ASSERT(r, nullptr != codec);
 
 #if (PNG_LIBPNG_VER_MAJOR > 1) || (PNG_LIBPNG_VER_MAJOR == 1 && PNG_LIBPNG_VER_MINOR >= 6)
     SkColorSpace* colorSpace = codec->getColorSpace();
     REPORTER_ASSERT(r, nullptr != colorSpace);
 
-    // No need to use almost equal here.  The color profile that we have extracted
-    // actually has a table of gammas.  And our current implementation guesses 2.2f.
-    SkFloat3 gammas = colorSpace->gamma();
-    REPORTER_ASSERT(r, 2.2f == gammas.fVec[0]);
-    REPORTER_ASSERT(r, 2.2f == gammas.fVec[1]);
-    REPORTER_ASSERT(r, 2.2f == gammas.fVec[2]);
+    // The color profile that we have extracted has represents gamma with a lookup table.
+    // So we expect the gamma value to be zero.
+    const SkColorSpace::SkGammas& gammas = colorSpace->gammas();
+    REPORTER_ASSERT(r, 0.0f == gammas.red());
+    REPORTER_ASSERT(r, 0.0f == gammas.green());
+    REPORTER_ASSERT(r, 0.0f == gammas.blue());
 
     // These nine values were extracted from the color profile in isolation (before
     // we embedded it in the png).  Here we check that we still extract the same values.
     SkFloat3x3 xyz = colorSpace->xyz();
     REPORTER_ASSERT(r, almost_equal(0.436066f, xyz.fMat[0]));
     REPORTER_ASSERT(r, almost_equal(0.222488f, xyz.fMat[1]));
     REPORTER_ASSERT(r, almost_equal(0.013916f, xyz.fMat[2]));
     REPORTER_ASSERT(r, almost_equal(0.385147f, xyz.fMat[3]));
     REPORTER_ASSERT(r, almost_equal(0.716873f, xyz.fMat[4]));
     REPORTER_ASSERT(r, almost_equal(0.0970764f, xyz.fMat[5]));
@@ skipping 14 matching lines @@
     REPORTER_ASSERT(r, nullptr != codec);
     if (!codec) {
         return;
     }
 
     SkColorSpace* colorSpace = codec->getColorSpace();
     REPORTER_ASSERT(r, nullptr != colorSpace);
 
     // It's important to use almost equal here.  This profile sets gamma as
     // 563 / 256, which actually comes out to about 2.19922.
-    SkFloat3 gammas = colorSpace->gamma();
-    REPORTER_ASSERT(r, almost_equal(2.2f, gammas.fVec[0]));
-    REPORTER_ASSERT(r, almost_equal(2.2f, gammas.fVec[1]));
-    REPORTER_ASSERT(r, almost_equal(2.2f, gammas.fVec[2]));
+    const SkColorSpace::SkGammas& gammas = colorSpace->gammas();
+    REPORTER_ASSERT(r, almost_equal(2.2f, gammas.red()));
+    REPORTER_ASSERT(r, almost_equal(2.2f, gammas.green()));
+    REPORTER_ASSERT(r, almost_equal(2.2f, gammas.blue()));
 
     // These nine values were extracted from the color profile.  Until we know any
     // better, we'll assume these are the right values and test that we continue
     // to extract them properly.
     SkFloat3x3 xyz = colorSpace->xyz();
     REPORTER_ASSERT(r, almost_equal(0.385117f, xyz.fMat[0]));
     REPORTER_ASSERT(r, almost_equal(0.716904f, xyz.fMat[1]));
     REPORTER_ASSERT(r, almost_equal(0.0970612f, xyz.fMat[2]));
     REPORTER_ASSERT(r, almost_equal(0.143051f, xyz.fMat[3]));
     REPORTER_ASSERT(r, almost_equal(0.0606079f, xyz.fMat[4]));
     REPORTER_ASSERT(r, almost_equal(0.713913f, xyz.fMat[5]));
     REPORTER_ASSERT(r, almost_equal(0.436035f, xyz.fMat[6]));
     REPORTER_ASSERT(r, almost_equal(0.222488f, xyz.fMat[7]));
     REPORTER_ASSERT(r, almost_equal(0.013916f, xyz.fMat[8]));
 }