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Unified Diff: src/core/SkColorSpaceXformPriv.h

Issue 2449243003: Initial implementation of a SkColorSpace_A2B xform (Closed)
Patch Set: responding to comments Created 4 years, 1 month ago
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Index: src/core/SkColorSpaceXformPriv.h
diff --git a/src/core/SkColorSpaceXformPriv.h b/src/core/SkColorSpaceXformPriv.h
new file mode 100644
index 0000000000000000000000000000000000000000..1cb533c9f3e8f1f97bdd83c202f6500e2832e3c2
--- /dev/null
+++ b/src/core/SkColorSpaceXformPriv.h
@@ -0,0 +1,281 @@
+/*
+ * 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 SkColorSpaceXformPriv_DEFINED
+#define SkColorSpaceXformPriv_DEFINED
+
+#include "SkColorSpace_Base.h"
+#include "SkHalf.h"
+#include "SkSRGB.h"
+
+#define AI SK_ALWAYS_INLINE
+
+#define SkCSXformPrintfDefined 0
+#define SkCSXformPrintf(...)
+
+static const int kDstGammaTableSize = SkColorSpaceXform_Base::kDstGammaTableSize;
+
+// Interpolating lookup in a variably sized table.
+static AI float interp_lut(float input, const float* table, int tableSize) {
+ float index = input * (tableSize - 1);
+ float diff = index - sk_float_floor2int(index);
+ return table[(int) sk_float_floor2int(index)] * (1.0f - diff) +
+ table[(int) sk_float_ceil2int(index)] * diff;
+}
+
+
+static AI void transform_gamut(const Sk4f& r, const Sk4f& g, const Sk4f& b, const Sk4f& a,
+ const Sk4f& rXgXbX, const Sk4f& rYgYbY, const Sk4f& rZgZbZ,
+ Sk4f& dr, Sk4f& dg, Sk4f& db, Sk4f& da) {
+ dr = rXgXbX[0]*r + rYgYbY[0]*g + rZgZbZ[0]*b;
+ dg = rXgXbX[1]*r + rYgYbY[1]*g + rZgZbZ[1]*b;
+ db = rXgXbX[2]*r + rYgYbY[2]*g + rZgZbZ[2]*b;
+ da = a;
+}
+
+static AI void translate_gamut(const Sk4f& rTgTbT, Sk4f& dr, Sk4f& dg, Sk4f& db) {
+ dr = dr + rTgTbT[0];
+ dg = dg + rTgTbT[1];
+ db = db + rTgTbT[2];
+}
+
+static AI void load_matrix(const float matrix[16],
+ Sk4f& rXgXbX, Sk4f& rYgYbY, Sk4f& rZgZbZ, Sk4f& rTgTbT) {
+ rXgXbX = Sk4f::Load(matrix + 0);
+ rYgYbY = Sk4f::Load(matrix + 4);
+ rZgZbZ = Sk4f::Load(matrix + 8);
+ rTgTbT = Sk4f::Load(matrix + 12);
+}
+
+
+enum Order {
+ kRGBA_Order,
+ kBGRA_Order,
+};
+
+static AI void set_rb_shifts(Order kOrder, int* kRShift, int* kBShift) {
+ if (kRGBA_Order == kOrder) {
+ *kRShift = 0;
+ *kBShift = 16;
+ } else {
+ *kRShift = 16;
+ *kBShift = 0;
+ }
+}
+
+template <Order kOrder>
+static AI void load_rgb_linear(const uint32_t* src, Sk4f& r, Sk4f& g, Sk4f& b, Sk4f& a,
+ const float* const[3]) {
+ int kRShift, kGShift = 8, kBShift;
+ set_rb_shifts(kOrder, &kRShift, &kBShift);
+ r = (1.0f / 255.0f) * SkNx_cast<float>((Sk4u::Load(src) >> kRShift) & 0xFF);
+ g = (1.0f / 255.0f) * SkNx_cast<float>((Sk4u::Load(src) >> kGShift) & 0xFF);
+ b = (1.0f / 255.0f) * SkNx_cast<float>((Sk4u::Load(src) >> kBShift) & 0xFF);
+ a = 0.0f; // Don't let the compiler complain that |a| is uninitialized.
+}
+
+template <Order kOrder>
+static AI void load_rgba_linear(const uint32_t* src, Sk4f& r, Sk4f& g, Sk4f& b, Sk4f& a,
+ const float* const[3]) {
+ int kRShift, kGShift = 8, kBShift;
+ set_rb_shifts(kOrder, &kRShift, &kBShift);
+ r = (1.0f / 255.0f) * SkNx_cast<float>((Sk4u::Load(src) >> kRShift) & 0xFF);
+ g = (1.0f / 255.0f) * SkNx_cast<float>((Sk4u::Load(src) >> kGShift) & 0xFF);
+ b = (1.0f / 255.0f) * SkNx_cast<float>((Sk4u::Load(src) >> kBShift) & 0xFF);
+ a = (1.0f / 255.0f) * SkNx_cast<float>((Sk4u::Load(src) >> 24));
+}
+
+static AI void premultiply(Sk4f& dr, Sk4f& dg, Sk4f& db, const Sk4f& da) {
+ dr = da * dr;
+ dg = da * dg;
+ db = da * db;
+}
+
+template <Order kOrder>
+static AI void store_srgb(void* dst, const uint32_t* src, Sk4f& dr, Sk4f& dg, Sk4f& db, Sk4f&,
+ const uint8_t* const[3]) {
+ int kRShift, kGShift = 8, kBShift;
+ set_rb_shifts(kOrder, &kRShift, &kBShift);
+ dr = sk_linear_to_srgb_needs_trunc(dr);
+ dg = sk_linear_to_srgb_needs_trunc(dg);
+ db = sk_linear_to_srgb_needs_trunc(db);
+
+ dr = sk_clamp_0_255(dr);
+ dg = sk_clamp_0_255(dg);
+ db = sk_clamp_0_255(db);
+
+ Sk4i da = Sk4i::Load(src) & 0xFF000000;
+
+ Sk4i rgba = (SkNx_cast<int>(dr) << kRShift)
+ | (SkNx_cast<int>(dg) << kGShift)
+ | (SkNx_cast<int>(db) << kBShift)
+ | (da );
+ rgba.store(dst);
+}
+
+static AI Sk4f linear_to_2dot2(const Sk4f& x) {
+ // x^(29/64) is a very good approximation of the true value, x^(1/2.2).
+ auto x2 = x.rsqrt(), // x^(-1/2)
+ x32 = x2.rsqrt().rsqrt().rsqrt().rsqrt(), // x^(-1/32)
+ x64 = x32.rsqrt(); // x^(+1/64)
+
+ // 29 = 32 - 2 - 1
+ return 255.0f * x2.invert() * x32 * x64.invert();
+}
+
+template <Order kOrder>
+static AI void store_2dot2(void* dst, const uint32_t* src, Sk4f& dr, Sk4f& dg, Sk4f& db, Sk4f&,
+ const uint8_t* const[3]) {
+ int kRShift, kGShift = 8, kBShift;
+ set_rb_shifts(kOrder, &kRShift, &kBShift);
+ dr = linear_to_2dot2(dr);
+ dg = linear_to_2dot2(dg);
+ db = linear_to_2dot2(db);
+
+ dr = sk_clamp_0_255(dr);
+ dg = sk_clamp_0_255(dg);
+ db = sk_clamp_0_255(db);
+
+ Sk4i da = Sk4i::Load(src) & 0xFF000000;
+
+ Sk4i rgba = (Sk4f_round(dr) << kRShift)
+ | (Sk4f_round(dg) << kGShift)
+ | (Sk4f_round(db) << kBShift)
+ | (da );
+ rgba.store(dst);
+}
+
+template <Order kOrder>
+static AI void store_linear(void* dst, const uint32_t* src, Sk4f& dr, Sk4f& dg, Sk4f& db, Sk4f&,
+ const uint8_t* const[3]) {
+ int kRShift, kGShift = 8, kBShift;
+ set_rb_shifts(kOrder, &kRShift, &kBShift);
+ dr = sk_clamp_0_255(255.0f * dr);
+ dg = sk_clamp_0_255(255.0f * dg);
+ db = sk_clamp_0_255(255.0f * db);
+
+ Sk4i da = Sk4i::Load(src) & 0xFF000000;
+
+ Sk4i rgba = (Sk4f_round(dr) << kRShift)
+ | (Sk4f_round(dg) << kGShift)
+ | (Sk4f_round(db) << kBShift)
+ | (da );
+ rgba.store(dst);
+}
+
+template <Order kOrder>
+static AI void store_f16(void* dst, const uint32_t* src, Sk4f& dr, Sk4f& dg, Sk4f& db, Sk4f& da,
+ const uint8_t* const[3]) {
+ Sk4h::Store4(dst, SkFloatToHalf_finite_ftz(dr),
+ SkFloatToHalf_finite_ftz(dg),
+ SkFloatToHalf_finite_ftz(db),
+ SkFloatToHalf_finite_ftz(da));
+}
+
+template <Order kOrder>
+static AI void store_f32(void* dst, const uint32_t* src, Sk4f& dr, Sk4f& dg, Sk4f& db, Sk4f& da,
+ const uint8_t* const[3]) {
+ Sk4f::Store4(dst, dr, dg, db, da);
+}
+
+template <Order kOrder>
+static AI void store_f16_opaque(void* dst, const uint32_t* src, Sk4f& dr, Sk4f& dg, Sk4f& db,
+ Sk4f&, const uint8_t* const[3]) {
+ Sk4h::Store4(dst, SkFloatToHalf_finite_ftz(dr),
+ SkFloatToHalf_finite_ftz(dg),
+ SkFloatToHalf_finite_ftz(db),
+ SK_Half1);
+}
+
+template <Order kOrder>
+static AI void store_generic(void* dst, const uint32_t* src, Sk4f& dr, Sk4f& dg, Sk4f& db, Sk4f&,
+ const uint8_t* const dstTables[3]) {
+ int kRShift, kGShift = 8, kBShift;
+ set_rb_shifts(kOrder, &kRShift, &kBShift);
+ dr = Sk4f::Min(Sk4f::Max(1023.0f * dr, 0.0f), 1023.0f);
+ dg = Sk4f::Min(Sk4f::Max(1023.0f * dg, 0.0f), 1023.0f);
+ db = Sk4f::Min(Sk4f::Max(1023.0f * db, 0.0f), 1023.0f);
+
+ Sk4i ir = Sk4f_round(dr);
+ Sk4i ig = Sk4f_round(dg);
+ Sk4i ib = Sk4f_round(db);
+
+ Sk4i da = Sk4i::Load(src) & 0xFF000000;
+
+ uint32_t* dst32 = (uint32_t*) dst;
+ dst32[0] = dstTables[0][ir[0]] << kRShift
+ | dstTables[1][ig[0]] << kGShift
+ | dstTables[2][ib[0]] << kBShift
+ | da[0];
+ dst32[1] = dstTables[0][ir[1]] << kRShift
+ | dstTables[1][ig[1]] << kGShift
+ | dstTables[2][ib[1]] << kBShift
+ | da[1];
+ dst32[2] = dstTables[0][ir[2]] << kRShift
+ | dstTables[1][ig[2]] << kGShift
+ | dstTables[2][ib[2]] << kBShift
+ | da[2];
+ dst32[3] = dstTables[0][ir[3]] << kRShift
+ | dstTables[1][ig[3]] << kGShift
+ | dstTables[2][ib[3]] << kBShift
+ | da[3];
+}
+
+typedef decltype(load_rgb_linear<kRGBA_Order> )* LoadFn;
+typedef decltype(store_linear<kRGBA_Order> )* StoreFn;
+
+static AI int num_tables(SkColorSpace_XYZ* space) {
+ switch (space->gammaNamed()) {
+ case kSRGB_SkGammaNamed:
+ case k2Dot2Curve_SkGammaNamed:
+ case kLinear_SkGammaNamed:
+ return 0;
+ default: {
+ const SkGammas* gammas = space->gammas();
+ SkASSERT(gammas);
+
+ bool gammasAreMatching = (gammas->type(0) == gammas->type(1)) &&
+ (gammas->data(0) == gammas->data(1)) &&
+ (gammas->type(0) == gammas->type(2)) &&
+ (gammas->data(0) == gammas->data(2));
+
+ // It's likely that each component will have the same gamma. In this case,
+ // we only need to build one table.
+ return gammasAreMatching ? 1 : 3;
+ }
+ }
+}
+
+// Inverse table lookup. Ex: what index corresponds to the input value? This will
+// have strange results when the table is non-increasing. But any sane gamma
+// function will be increasing.
+static float inverse_interp_lut(float input, const float* table, int tableSize) {
+ if (input <= table[0]) {
+ return table[0];
+ } else if (input >= table[tableSize - 1]) {
+ return 1.0f;
+ }
+
+ for (int i = 1; i < tableSize; i++) {
+ if (table[i] >= input) {
+ // We are guaranteed that input is greater than table[i - 1].
+ float diff = input - table[i - 1];
+ float distance = table[i] - table[i - 1];
+ float index = (i - 1) + diff / distance;
+ return index / (tableSize - 1);
+ }
+ }
+
+ // Should be unreachable, since we'll return before the loop if input is
+ // larger than the last entry.
+ SkASSERT(false);
+ return 0.0f;
+}
+
+#undef AI
+
+#endif

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