GPU version of onMakeColorSpace

New fragment processor that implements end-to-end
color space conversion, with nonlinear blending.

BUG=skia:6242

Change-Id: Ied86170fc28537a2bc209d57530d3ded48b467a9
Reviewed-on: https://skia-review.googlesource.com/9543
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Matt Sarett <msarett@google.com>
Reviewed-by: Robert Phillips <robertphillips@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>

1 files changed, 72 insertions, 0 deletions

diff --git a/src/gpu/effects/GrNonlinearColorSpaceXformEffect.h b/src/gpu/effects/GrNonlinearColorSpaceXformEffect.h
new file mode 100644
index 0000000000..36f778398e
--- /dev/null
+++ b/src/gpu/effects/GrNonlinearColorSpaceXformEffect.h
@@ -0,0 +1,72 @@
+/*
+ * Copyright 2017 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef GrNonlinearColorSpaceXformEffect_DEFINED
+#define GrNonlinearColorSpaceXformEffect_DEFINED
+
+#include "GrFragmentProcessor.h"
+#include "SkColorSpace.h"
+#include "SkMatrix44.h"
+
+/**
+ * The output of this effect is the input, transformed into a different color space.
+ * This effect is used for nonlinear blending color space support - it does not assume HW sRGB
+ * capabilities, and performs both the source and destination transfer functions numerically in
+ * the shader. Any parametric transfer function is supported. Because of the nonlinear blending,
+ * premultiplication is also nonlinear - source pixels are unpremultiplied before the source
+ * transfer function, and then premultiplied after the destination transfer function.
+ */
+class GrNonlinearColorSpaceXformEffect : public GrFragmentProcessor {
+public:
+    /**
+     * The conversion effect is only well defined with a valid source and destination color space.
+     * This will return nullptr if either space is nullptr, if both spaces are equal, or if either
+     * space has a non-parametric transfer funcion (e.g. lookup table or A2B).
+     */
+    static sk_sp<GrFragmentProcessor> Make(const SkColorSpace* src, const SkColorSpace* dst);
+
+    const char* name() const override { return "NonlinearColorSpaceXform"; }
+
+    static const int kNumTransferFnCoeffs = 7;
+
+    /**
+     * Flags that specify which operations are performed for one particular conversion.
+     * Some color space pairs may not need all operations, if one or both transfer functions
+     * is linear, or if the gamuts are the same.
+     */
+    enum Ops {
+        kSrcTransfer_Op = 0x1,
+        kGamutXform_Op  = 0x2,
+        kDstTransfer_Op = 0x4,
+    };
+
+    uint32_t ops() const { return fOps; }
+    const float* srcTransferFnCoeffs() const { return fSrcTransferFnCoeffs; }
+    const float* dstTransferFnCoeffs() const { return fDstTransferFnCoeffs; }
+    const SkMatrix44& gamutXform() const { return fGamutXform; }
+
+private:
+    GrNonlinearColorSpaceXformEffect(uint32_t ops,
+                                     const SkColorSpaceTransferFn& srcTransferFn,
+                                     const SkColorSpaceTransferFn& dstTransferFn,
+                                     const SkMatrix44& gamutXform);
+
+    GrGLSLFragmentProcessor* onCreateGLSLInstance() const override;
+    void onGetGLSLProcessorKey(const GrShaderCaps&, GrProcessorKeyBuilder*) const override;
+    bool onIsEqual(const GrFragmentProcessor&) const override;
+
+    float fSrcTransferFnCoeffs[kNumTransferFnCoeffs];
+    float fDstTransferFnCoeffs[kNumTransferFnCoeffs];
+    SkMatrix44 fGamutXform;
+    uint32_t fOps;
+
+    GR_DECLARE_FRAGMENT_PROCESSOR_TEST;
+
+    typedef GrFragmentProcessor INHERITED;
+};
+
+#endif