Refactored SkColorSpace and added in a Lab PCS GM

The refactoring breaks off A2B0 tag support into a separate
subclass of SkColorSpace_Base, while keeping the current
(besides CLUT) functionality in a XYZTRC subclass.

ICC profile loading is now aware of this and creates the A2B0
subclass when SkColorSpace::NewICC() is called on a profile
in need of the A2B0 functionality.

The LabPCSDemo GM loads a .icc profile containing a LAB PCS and
then runs a Lab->XYZ conversion on an image using it so we can
display it and test out the A2B0 SkColorSpace functionality,
sans a/b/m-curves, as well as the Lab->XYZ conversion code.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2389983002

Review-Url: https://codereview.chromium.org/2389983002

1 files changed, 102 insertions, 0 deletions

diff --git a/src/core/SkColorSpace_A2B.h b/src/core/SkColorSpace_A2B.h
new file mode 100644
index 0000000000..0fc952bd6c
--- /dev/null
+++ b/src/core/SkColorSpace_A2B.h
@@ -0,0 +1,102 @@
+/*
+ * Copyright 2016 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkColorSpace_A2B_DEFINED
+#define SkColorSpace_A2B_DEFINED
+
+#include "SkColorSpace_Base.h"
+
+// An alternative SkColorSpace that represents all the color space data that
+// is stored in an A2B0 ICC tag. This allows us to use alternative profile
+// connection spaces (CIELAB instead of just CIEXYZ), use color-lookup-tables
+// to do color space transformations not representable as TRC functions or
+// matrix operations, as well as have multiple TRC functions. The CLUT also has
+// the potential to allow conversion from input color spaces with a different
+// number of channels such as CMYK (4) or GRAY (1), but that is not supported yet.
+//
+// Evaluation is done: A-curve => CLUT => M-curve => Matrix => B-curve
+//
+// There are also multi-processing-elements in the A2B0 tag which allow you to
+// combine these 3 primitives (TRC, CLUT, matrix) in any order/quantitiy,
+// but support for that is not implemented.
+class SkColorSpace_A2B : public SkColorSpace_Base {
+public:
+    const SkMatrix44* toXYZD50() const override {
+        // the matrix specified in A2B0 profiles is not necessarily
+        // a to-XYZ matrix, as to-Lab is supported as well so returning
+        // that could be misleading. Additionally, B-curves are applied
+        // after the matrix is, but a toXYZD50 matrix is the last thing
+        // applied in order to get into the (XYZ) profile connection space.
+        return nullptr;
+    }
+
+    const SkMatrix44* fromXYZD50() const override {
+        // See toXYZD50()'s comment. Also, A2B0 profiles are not supported
+        // as destination color spaces, so an inverse matrix is never wanted.
+        return nullptr;
+    }
+    
+    bool onGammaCloseToSRGB() const override {
+        // There is no single gamma curve in an A2B0 profile
+        return false;
+    }
+    
+    bool onGammaIsLinear() const override {
+        // There is no single gamma curve in an A2B0 profile
+        return false;
+    }
+
+    SkGammaNamed aCurveNamed() const { return fACurveNamed; }
+
+    const SkGammas* aCurve() const { return fACurve.get(); }
+
+    const SkColorLookUpTable* colorLUT() const { return fColorLUT.get(); }
+
+    SkGammaNamed mCurveNamed() const { return fMCurveNamed; }
+    
+    const SkGammas* mCurve() const { return fMCurve.get(); }
+
+    const SkMatrix44& matrix() const { return fMatrix; }
+
+    SkGammaNamed bCurveNamed() const { return fBCurveNamed; }
+    
+    const SkGammas* bCurve() const { return fBCurve.get(); }
+
+    // the intermediate profile connection space that this color space
+    // represents the transformation to
+    enum class PCS : uint8_t {
+        kLAB, // CIELAB
+        kXYZ  // CIEXYZ
+    };
+    
+    PCS pcs() const { return fPCS; }
+
+    Type type() const override { return Type::kA2B; }
+
+private:
+    SkColorSpace_A2B(SkGammaNamed aCurveNamed, sk_sp<SkGammas> aCurve,
+                     sk_sp<SkColorLookUpTable> colorLUT,
+                     SkGammaNamed mCurveNamed, sk_sp<SkGammas> mCurve,
+                     const SkMatrix44& matrix,
+                     SkGammaNamed bCurveNamed, sk_sp<SkGammas> bCurve,
+                     PCS pcs, sk_sp<SkData> profileData);
+
+    const SkGammaNamed        fACurveNamed;
+    sk_sp<SkGammas>           fACurve;
+    sk_sp<SkColorLookUpTable> fColorLUT;
+    const SkGammaNamed        fMCurveNamed;
+    sk_sp<SkGammas>           fMCurve;
+    SkMatrix44                fMatrix;
+    const SkGammaNamed        fBCurveNamed;
+    sk_sp<SkGammas>           fBCurve;
+    PCS                       fPCS;
+    
+    friend class SkColorSpace;
+    typedef SkColorSpace_Base INHERITED;
+};
+
+#endif