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-rw-r--r--include/core/SkColorSpace.h21
-rw-r--r--src/codec/SkPngCodec.cpp85
-rw-r--r--src/core/SkColorSpace.cpp76
-rw-r--r--tests/ColorSpaceTest.cpp20
4 files changed, 129 insertions, 73 deletions
diff --git a/include/core/SkColorSpace.h b/include/core/SkColorSpace.h
index a96f622095..9b990da966 100644
--- a/include/core/SkColorSpace.h
+++ b/include/core/SkColorSpace.h
@@ -13,6 +13,22 @@
class SkData;
+/**
+ * Describes a color gamut with primaries and a white point.
+ */
+struct SK_API SkColorSpacePrimaries {
+ float fRX, fRY;
+ float fGX, fGY;
+ float fBX, fBY;
+ float fWX, fWY;
+
+ /**
+ * Convert primaries and a white point to a toXYZD50 matrix, the preferred color gamut
+ * representation of SkColorSpace.
+ */
+ bool toXYZD50(SkMatrix44* toXYZD50) const;
+};
+
class SK_API SkColorSpace : public SkRefCnt {
public:
@@ -50,7 +66,10 @@ public:
};
/**
- * Create an SkColorSpace from a transfer function and a color gamut transform to D50 XYZ.
+ * Create an SkColorSpace from a transfer function and a color gamut.
+ *
+ * Transfer function is specified as linear or sRGB.
+ * Gamut is specified using the matrix transformation to XYZ D50.
*/
static sk_sp<SkColorSpace> NewRGB(RenderTargetGamma gamma, const SkMatrix44& toXYZD50);
diff --git a/src/codec/SkPngCodec.cpp b/src/codec/SkPngCodec.cpp
index dde49d037d..55a29604a9 100644
--- a/src/codec/SkPngCodec.cpp
+++ b/src/codec/SkPngCodec.cpp
@@ -322,63 +322,6 @@ static constexpr float gSRGB_toXYZD50[] {
0.0139f, 0.0971f, 0.7139f, // Rz, Gz, Bz
};
-static bool convert_to_D50(SkMatrix44* toXYZD50, float toXYZ[9], float whitePoint[2]) {
- float wX = whitePoint[0];
- float wY = whitePoint[1];
- if (wX < 0.0f || wY < 0.0f || (wX + wY > 1.0f)) {
- return false;
- }
-
- // Calculate the XYZ illuminant. Call this the src illuminant.
- float wZ = 1.0f - wX - wY;
- float scale = 1.0f / wY;
- // TODO (msarett):
- // What are common src illuminants? I'm guessing we will almost always see D65. Should
- // we go ahead and save a precomputed D65->D50 Bradford matrix? Should we exit early if
- // if the src illuminant is D50?
- SkVector3 srcXYZ = SkVector3::Make(wX * scale, 1.0f, wZ * scale);
-
- // The D50 illuminant.
- SkVector3 dstXYZ = SkVector3::Make(0.96422f, 1.0f, 0.82521f);
-
- // Calculate the chromatic adaptation matrix. We will use the Bradford method, thus
- // the matrices below. The Bradford method is used by Adobe and is widely considered
- // to be the best.
- // http://www.brucelindbloom.com/index.html?Eqn_ChromAdapt.html
- SkMatrix mA, mAInv;
- mA.setAll(0.8951f, 0.2664f, -0.1614f, -0.7502f, 1.7135f, 0.0367f, 0.0389f, -0.0685f, 1.0296f);
- mAInv.setAll(0.9869929f, -0.1470543f, 0.1599627f, 0.4323053f, 0.5183603f, 0.0492912f,
- -0.0085287f, 0.0400428f, 0.9684867f);
-
- // Map illuminant into cone response domain.
- SkVector3 srcCone;
- srcCone.fX = mA[0] * srcXYZ.fX + mA[1] * srcXYZ.fY + mA[2] * srcXYZ.fZ;
- srcCone.fY = mA[3] * srcXYZ.fX + mA[4] * srcXYZ.fY + mA[5] * srcXYZ.fZ;
- srcCone.fZ = mA[6] * srcXYZ.fX + mA[7] * srcXYZ.fY + mA[8] * srcXYZ.fZ;
- SkVector3 dstCone;
- dstCone.fX = mA[0] * dstXYZ.fX + mA[1] * dstXYZ.fY + mA[2] * dstXYZ.fZ;
- dstCone.fY = mA[3] * dstXYZ.fX + mA[4] * dstXYZ.fY + mA[5] * dstXYZ.fZ;
- dstCone.fZ = mA[6] * dstXYZ.fX + mA[7] * dstXYZ.fY + mA[8] * dstXYZ.fZ;
-
- SkMatrix DXToD50;
- DXToD50.setIdentity();
- DXToD50[0] = dstCone.fX / srcCone.fX;
- DXToD50[4] = dstCone.fY / srcCone.fY;
- DXToD50[8] = dstCone.fZ / srcCone.fZ;
- DXToD50.postConcat(mAInv);
- DXToD50.preConcat(mA);
-
- SkMatrix toXYZ3x3;
- toXYZ3x3.setAll(toXYZ[0], toXYZ[3], toXYZ[6], toXYZ[1], toXYZ[4], toXYZ[7], toXYZ[2], toXYZ[5],
- toXYZ[8]);
- toXYZ3x3.postConcat(DXToD50);
-
- toXYZD50->set3x3(toXYZ3x3[0], toXYZ3x3[3], toXYZ3x3[6],
- toXYZ3x3[1], toXYZ3x3[4], toXYZ3x3[7],
- toXYZ3x3[2], toXYZ3x3[5], toXYZ3x3[8]);
- return true;
-}
-
#endif // LIBPNG >= 1.6
// Returns a colorSpace object that represents any color space information in
@@ -416,26 +359,24 @@ sk_sp<SkColorSpace> read_color_space(png_structp png_ptr, png_infop info_ptr) {
}
// Next, check for chromaticities.
- png_fixed_point toXYZFixed[9];
- float toXYZ[9];
- png_fixed_point whitePointFixed[2];
- float whitePoint[2];
+ png_fixed_point chrm[8];
png_fixed_point gamma;
float gammas[3];
- if (png_get_cHRM_XYZ_fixed(png_ptr, info_ptr, &toXYZFixed[0], &toXYZFixed[1], &toXYZFixed[2],
- &toXYZFixed[3], &toXYZFixed[4], &toXYZFixed[5], &toXYZFixed[6],
- &toXYZFixed[7], &toXYZFixed[8]) &&
- png_get_cHRM_fixed(png_ptr, info_ptr, &whitePointFixed[0], &whitePointFixed[1], nullptr,
- nullptr, nullptr, nullptr, nullptr, nullptr))
+ if (png_get_cHRM_fixed(png_ptr, info_ptr, &chrm[0], &chrm[1], &chrm[2], &chrm[3], &chrm[4],
+ &chrm[5], &chrm[6], &chrm[7]))
{
- for (int i = 0; i < 9; i++) {
- toXYZ[i] = png_fixed_point_to_float(toXYZFixed[i]);
- }
- whitePoint[0] = png_fixed_point_to_float(whitePointFixed[0]);
- whitePoint[1] = png_fixed_point_to_float(whitePointFixed[1]);
+ SkColorSpacePrimaries primaries;
+ primaries.fRX = png_fixed_point_to_float(chrm[2]);
+ primaries.fRY = png_fixed_point_to_float(chrm[3]);
+ primaries.fGX = png_fixed_point_to_float(chrm[4]);
+ primaries.fGY = png_fixed_point_to_float(chrm[5]);
+ primaries.fBX = png_fixed_point_to_float(chrm[6]);
+ primaries.fBY = png_fixed_point_to_float(chrm[7]);
+ primaries.fWX = png_fixed_point_to_float(chrm[0]);
+ primaries.fWY = png_fixed_point_to_float(chrm[1]);
SkMatrix44 toXYZD50(SkMatrix44::kUninitialized_Constructor);
- if (!convert_to_D50(&toXYZD50, toXYZ, whitePoint)) {
+ if (!primaries.toXYZD50(&toXYZD50)) {
toXYZD50.set3x3RowMajorf(gSRGB_toXYZD50);
}
diff --git a/src/core/SkColorSpace.cpp b/src/core/SkColorSpace.cpp
index c6bf4b9431..66b980b8f9 100644
--- a/src/core/SkColorSpace.cpp
+++ b/src/core/SkColorSpace.cpp
@@ -9,6 +9,82 @@
#include "SkColorSpace_Base.h"
#include "SkColorSpacePriv.h"
#include "SkOnce.h"
+#include "SkPoint3.h"
+
+static inline bool is_zero_to_one(float v) {
+ return (0.0f <= v) && (v <= 1.0f);
+}
+
+bool SkColorSpacePrimaries::toXYZD50(SkMatrix44* toXYZ_D50) const {
+ if (!is_zero_to_one(fRX) || !is_zero_to_one(fRY) ||
+ !is_zero_to_one(fGX) || !is_zero_to_one(fGY) ||
+ !is_zero_to_one(fBX) || !is_zero_to_one(fBY) ||
+ !is_zero_to_one(fWX) || !is_zero_to_one(fWY))
+ {
+ return false;
+ }
+
+ // First, we need to convert xy values (primaries) to XYZ.
+ SkMatrix primaries;
+ primaries.setAll( fRX, fGX, fBX,
+ fRY, fGY, fBY,
+ 1.0f - fRX - fRY, 1.0f - fGX - fGY, 1.0f - fBX - fBY);
+ SkMatrix primariesInv;
+ if (!primaries.invert(&primariesInv)) {
+ return false;
+ }
+
+ // Assumes that Y is 1.0f.
+ SkVector3 wXYZ = SkVector3::Make(fWX / fWY, 1.0f, (1.0f - fWX - fWY) / fWY);
+ SkVector3 XYZ;
+ XYZ.fX = primariesInv[0] * wXYZ.fX + primariesInv[1] * wXYZ.fY + primariesInv[2] * wXYZ.fZ;
+ XYZ.fY = primariesInv[3] * wXYZ.fX + primariesInv[4] * wXYZ.fY + primariesInv[5] * wXYZ.fZ;
+ XYZ.fZ = primariesInv[6] * wXYZ.fX + primariesInv[7] * wXYZ.fY + primariesInv[8] * wXYZ.fZ;
+ SkMatrix toXYZ;
+ toXYZ.setAll(XYZ.fX, 0.0f, 0.0f,
+ 0.0f, XYZ.fY, 0.0f,
+ 0.0f, 0.0f, XYZ.fZ);
+ toXYZ.postConcat(primaries);
+
+ // Now convert toXYZ matrix to toXYZD50.
+ SkVector3 wXYZD50 = SkVector3::Make(0.96422f, 1.0f, 0.82521f);
+
+ // Calculate the chromatic adaptation matrix. We will use the Bradford method, thus
+ // the matrices below. The Bradford method is used by Adobe and is widely considered
+ // to be the best.
+ SkMatrix mA, mAInv;
+ mA.setAll(+0.8951f, +0.2664f, -0.1614f,
+ -0.7502f, +1.7135f, +0.0367f,
+ +0.0389f, -0.0685f, +1.0296f);
+ mAInv.setAll(+0.9869929f, -0.1470543f, +0.1599627f,
+ +0.4323053f, +0.5183603f, +0.0492912f,
+ -0.0085287f, +0.0400428f, +0.9684867f);
+
+ SkVector3 srcCone;
+ srcCone.fX = mA[0] * wXYZ.fX + mA[1] * wXYZ.fY + mA[2] * wXYZ.fZ;
+ srcCone.fY = mA[3] * wXYZ.fX + mA[4] * wXYZ.fY + mA[5] * wXYZ.fZ;
+ srcCone.fZ = mA[6] * wXYZ.fX + mA[7] * wXYZ.fY + mA[8] * wXYZ.fZ;
+ SkVector3 dstCone;
+ dstCone.fX = mA[0] * wXYZD50.fX + mA[1] * wXYZD50.fY + mA[2] * wXYZD50.fZ;
+ dstCone.fY = mA[3] * wXYZD50.fX + mA[4] * wXYZD50.fY + mA[5] * wXYZD50.fZ;
+ dstCone.fZ = mA[6] * wXYZD50.fX + mA[7] * wXYZD50.fY + mA[8] * wXYZD50.fZ;
+
+ SkMatrix DXToD50;
+ DXToD50.setIdentity();
+ DXToD50[0] = dstCone.fX / srcCone.fX;
+ DXToD50[4] = dstCone.fY / srcCone.fY;
+ DXToD50[8] = dstCone.fZ / srcCone.fZ;
+ DXToD50.postConcat(mAInv);
+ DXToD50.preConcat(mA);
+
+ toXYZ.postConcat(DXToD50);
+ toXYZ_D50->set3x3(toXYZ[0], toXYZ[3], toXYZ[6],
+ toXYZ[1], toXYZ[4], toXYZ[7],
+ toXYZ[2], toXYZ[5], toXYZ[8]);
+ return true;
+}
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
SkColorSpace_Base::SkColorSpace_Base(SkGammaNamed gammaNamed, const SkMatrix44& toXYZD50)
: fGammaNamed(gammaNamed)
diff --git a/tests/ColorSpaceTest.cpp b/tests/ColorSpaceTest.cpp
index a6ed9e3cf9..a4eab92f5d 100644
--- a/tests/ColorSpaceTest.cpp
+++ b/tests/ColorSpaceTest.cpp
@@ -271,3 +271,23 @@ DEF_TEST(ColorSpace_Equals, r) {
REPORTER_ASSERT(r, !SkColorSpace::Equals(upperRight.get(), adobe.get()));
REPORTER_ASSERT(r, !SkColorSpace::Equals(rgb1.get(), rgb2.get()));
}
+
+DEF_TEST(ColorSpace_Primaries, r) {
+ // sRGB primaries
+ SkColorSpacePrimaries primaries;
+ primaries.fRX = 0.64f;
+ primaries.fRY = 0.33f;
+ primaries.fGX = 0.30f;
+ primaries.fGY = 0.60f;
+ primaries.fBX = 0.15f;
+ primaries.fBY = 0.06f;
+ primaries.fWX = 0.3127f;
+ primaries.fWY = 0.3290f;
+
+ SkMatrix44 toXYZ(SkMatrix44::kUninitialized_Constructor);
+ bool result = primaries.toXYZD50(&toXYZ);
+ REPORTER_ASSERT(r, result);
+
+ sk_sp<SkColorSpace> space = SkColorSpace::NewRGB(SkColorSpace::kSRGB_RenderTargetGamma, toXYZ);
+ REPORTER_ASSERT(r, SkColorSpace::NewNamed(SkColorSpace::kSRGB_Named) == space);
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-06-07 00:26:52 +0000