diff options
| -rw-r--r-- | src/codec/SkPngCodec.cpp | 99 |
1 files changed, 80 insertions, 19 deletions
diff --git a/src/codec/SkPngCodec.cpp b/src/codec/SkPngCodec.cpp index 32308b2630..ee72af58ad 100644 --- a/src/codec/SkPngCodec.cpp +++ b/src/codec/SkPngCodec.cpp @@ -13,6 +13,7 @@ #include "SkMath.h" #include "SkOpts.h" #include "SkPngCodec.h" +#include "SkPoint3.h" #include "SkSize.h" #include "SkStream.h" #include "SkSwizzler.h" @@ -178,6 +179,62 @@ static constexpr float gSRGB_toXYZD50[] { 0.1430f, 0.0606f, 0.7139f, // * B }; +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[1], toXYZ3x3[2], toXYZ3x3[3], toXYZ3x3[4], toXYZ3x3[5], + toXYZ3x3[6], toXYZ3x3[7], toXYZ3x3[8]); + return true; +} + // Returns a colorSpace object that represents any color space information in // the encoded data. If the encoded data contains no color space, this will // return NULL. @@ -213,24 +270,28 @@ sk_sp<SkColorSpace> read_color_space(png_structp png_ptr, png_infop info_ptr) { } // Next, check for chromaticities. - png_fixed_point XYZ[9]; - float toXYZD50[9]; + png_fixed_point toXYZFixed[9]; + float toXYZ[9]; + png_fixed_point whitePointFixed[2]; + float whitePoint[2]; png_fixed_point gamma; float gammas[3]; - if (png_get_cHRM_XYZ_fixed(png_ptr, info_ptr, &XYZ[0], &XYZ[1], &XYZ[2], &XYZ[3], &XYZ[4], - &XYZ[5], &XYZ[6], &XYZ[7], &XYZ[8])) { - - // FIXME (msarett): Here we are treating XYZ values as D50 even though the color - // temperature is unspecified. I suspect that this assumption - // is most often ok, but we could also calculate the color - // temperature (D value) and then convert the XYZ to D50. Maybe - // we should add a new constructor to SkColorSpace that accepts - // XYZ with D-Unkown? + 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)) + { for (int i = 0; i < 9; i++) { - toXYZD50[i] = png_fixed_point_to_float(XYZ[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]); + + SkMatrix44 toXYZD50(SkMatrix44::kUninitialized_Constructor); + if (!convert_to_D50(&toXYZD50, toXYZ, whitePoint)) { + toXYZD50.set3x3RowMajorf(gSRGB_toXYZD50); } - SkMatrix44 mat(SkMatrix44::kUninitialized_Constructor); - mat.set3x3RowMajorf(toXYZD50); if (PNG_INFO_gAMA == png_get_gAMA_fixed(png_ptr, info_ptr, &gamma)) { float value = png_inverted_fixed_point_to_float(gamma); @@ -238,12 +299,12 @@ sk_sp<SkColorSpace> read_color_space(png_structp png_ptr, png_infop info_ptr) { gammas[1] = value; gammas[2] = value; - return SkColorSpace_Base::NewRGB(gammas, mat); + return SkColorSpace_Base::NewRGB(gammas, toXYZD50); } // Default to sRGB gamma if the image has color space information, // but does not specify gamma. - return SkColorSpace::NewRGB(SkColorSpace::kSRGB_GammaNamed, mat); + return SkColorSpace::NewRGB(SkColorSpace::kSRGB_GammaNamed, toXYZD50); } // Last, check for gamma. @@ -256,10 +317,10 @@ sk_sp<SkColorSpace> read_color_space(png_structp png_ptr, png_infop info_ptr) { gammas[2] = value; // Since there is no cHRM, we will guess sRGB gamut. - SkMatrix44 mat(SkMatrix44::kUninitialized_Constructor); - mat.set3x3RowMajorf(gSRGB_toXYZD50); + SkMatrix44 toXYZD50(SkMatrix44::kUninitialized_Constructor); + toXYZD50.set3x3RowMajorf(gSRGB_toXYZD50); - return SkColorSpace_Base::NewRGB(gammas, mat); + return SkColorSpace_Base::NewRGB(gammas, toXYZD50); } #endif // LIBPNG >= 1.6 |