| /* |
| * 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 <math.h> |
| |
| #include "SkColorSpace_Base.h" |
| |
| #define SkColorSpacePrintf(...) |
| |
| static constexpr float gSRGB_toXYZD50[] { |
| 0.4360747f, 0.3850649f, 0.1430804f, // Rx, Gx, Bx |
| 0.2225045f, 0.7168786f, 0.0606169f, // Ry, Gy, Gz |
| 0.0139322f, 0.0971045f, 0.7141733f, // Rz, Gz, Bz |
| }; |
| |
| static constexpr float gAdobeRGB_toXYZD50[] { |
| 0.6097559f, 0.2052401f, 0.1492240f, // Rx, Gx, Bx |
| 0.3111242f, 0.6256560f, 0.0632197f, // Ry, Gy, Gz |
| 0.0194811f, 0.0608902f, 0.7448387f, // Rz, Gz, Bz |
| }; |
| |
| static inline bool color_space_almost_equal(float a, float b) { |
| return SkTAbs(a - b) < 0.01f; |
| } |
| |
| static inline float add_epsilon(float v) { |
| return v + FLT_MIN; |
| } |
| |
| static inline bool is_zero_to_one(float v) { |
| // Because we allow a value just barely larger than 1, the client can use an |
| // entirely linear transfer function. |
| return (0.0f <= v) && (v <= add_epsilon(1.0f)); |
| } |
| |
| static inline bool is_valid_transfer_fn(const SkColorSpaceTransferFn& coeffs) { |
| if (SkScalarIsNaN(coeffs.fA) || SkScalarIsNaN(coeffs.fB) || |
| SkScalarIsNaN(coeffs.fC) || SkScalarIsNaN(coeffs.fD) || |
| SkScalarIsNaN(coeffs.fE) || SkScalarIsNaN(coeffs.fF) || |
| SkScalarIsNaN(coeffs.fG)) |
| { |
| return false; |
| } |
| |
| if (!is_zero_to_one(coeffs.fD)) { |
| return false; |
| } |
| |
| if (coeffs.fD == 0.0f) { |
| // Y = (aX + b)^g + c for always |
| if (0.0f == coeffs.fA || 0.0f == coeffs.fG) { |
| SkColorSpacePrintf("A or G is zero, constant transfer function " |
| "is nonsense"); |
| return false; |
| } |
| } |
| |
| if (coeffs.fD >= 1.0f) { |
| // Y = eX + f for always |
| if (0.0f == coeffs.fE) { |
| SkColorSpacePrintf("E is zero, constant transfer function is " |
| "nonsense"); |
| return false; |
| } |
| } |
| |
| if ((0.0f == coeffs.fA || 0.0f == coeffs.fG) && 0.0f == coeffs.fC) { |
| SkColorSpacePrintf("A or G, and E are zero, constant transfer function " |
| "is nonsense"); |
| return false; |
| } |
| |
| if (coeffs.fC < 0.0f) { |
| SkColorSpacePrintf("Transfer function must be increasing"); |
| return false; |
| } |
| |
| if (coeffs.fA < 0.0f || coeffs.fG < 0.0f) { |
| SkColorSpacePrintf("Transfer function must be positive or increasing"); |
| return false; |
| } |
| |
| return true; |
| } |
| |
| static inline bool is_almost_srgb(const SkColorSpaceTransferFn& coeffs) { |
| return color_space_almost_equal(1.0f / 1.055f, coeffs.fA) && |
| color_space_almost_equal(0.055f / 1.055f, coeffs.fB) && |
| color_space_almost_equal(1.0f / 12.92f, coeffs.fC) && |
| color_space_almost_equal(0.04045f, coeffs.fD) && |
| color_space_almost_equal(0.00000f, coeffs.fE) && |
| color_space_almost_equal(0.00000f, coeffs.fF) && |
| color_space_almost_equal(2.40000f, coeffs.fG); |
| } |
| |
| static inline bool is_almost_2dot2(const SkColorSpaceTransferFn& coeffs) { |
| return color_space_almost_equal(1.0f, coeffs.fA) && |
| color_space_almost_equal(0.0f, coeffs.fB) && |
| color_space_almost_equal(0.0f, coeffs.fC) && |
| color_space_almost_equal(0.0f, coeffs.fD) && |
| color_space_almost_equal(0.0f, coeffs.fE) && |
| color_space_almost_equal(0.0f, coeffs.fF) && |
| color_space_almost_equal(2.2f, coeffs.fG); |
| } |
| |
| static inline void value_to_parametric(SkColorSpaceTransferFn* coeffs, float exponent) { |
| coeffs->fA = 1.0f; |
| coeffs->fB = 0.0f; |
| coeffs->fC = 0.0f; |
| coeffs->fD = 0.0f; |
| coeffs->fE = 0.0f; |
| coeffs->fF = 0.0f; |
| coeffs->fG = exponent; |
| } |
| |
| static inline bool named_to_parametric(SkColorSpaceTransferFn* coeffs, |
| SkGammaNamed gammaNamed) { |
| switch (gammaNamed) { |
| case kSRGB_SkGammaNamed: |
| coeffs->fA = 1.0f / 1.055f; |
| coeffs->fB = 0.055f / 1.055f; |
| coeffs->fC = 1.0f / 12.92f; |
| coeffs->fD = 0.04045f; |
| coeffs->fE = 0.0f; |
| coeffs->fF = 0.0f; |
| coeffs->fG = 2.4f; |
| return true; |
| case k2Dot2Curve_SkGammaNamed: |
| value_to_parametric(coeffs, 2.2f); |
| return true; |
| case kLinear_SkGammaNamed: |
| coeffs->fA = 0.0f; |
| coeffs->fB = 0.0f; |
| coeffs->fC = 1.0f; |
| // Make sure that we use the linear segment of the transfer function even |
| // when the x-value is 1.0f. |
| coeffs->fD = add_epsilon(1.0f); |
| coeffs->fE = 0.0f; |
| coeffs->fF = 0.0f; |
| coeffs->fG = 0.0f; |
| return true; |
| default: |
| return false; |
| } |
| } |