diff options
Diffstat (limited to 'src/opts/SkColorXform_opts.h')
-rw-r--r-- | src/opts/SkColorXform_opts.h | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/src/opts/SkColorXform_opts.h b/src/opts/SkColorXform_opts.h index 9904b3ef93..74aa53ce7a 100644 --- a/src/opts/SkColorXform_opts.h +++ b/src/opts/SkColorXform_opts.h @@ -10,8 +10,8 @@ #include "SkNx.h" #include "SkColorPriv.h" -#include "SkSRGB.h" +extern const float sk_linear_from_srgb[256]; extern const float sk_linear_from_2dot2[256]; namespace SK_OPTS_NS { @@ -26,6 +26,26 @@ static Sk4f linear_to_2dot2(const Sk4f& x) { return 255.0f * x2.invert() * x32 * x64.invert(); } +static Sk4f linear_to_srgb(const Sk4f& x) { + // Approximation of the sRGB gamma curve (within 1 when scaled to 8-bit pixels). + // For 0.00000f <= x < 0.00349f, 12.92 * x + // For 0.00349f <= x <= 1.00000f, 0.679*(x.^0.5) + 0.423*x.^(0.25) - 0.101 + // Note that 0.00349 was selected because it is a point where both functions produce the + // same pixel value when rounded. + auto rsqrt = x.rsqrt(), + sqrt = rsqrt.invert(), + ftrt = rsqrt.rsqrt(); + + auto hi = (-0.101115084998961f * 255.0f) + + (+0.678513029959381f * 255.0f) * sqrt + + (+0.422602055039580f * 255.0f) * ftrt; + + auto lo = (12.92f * 255.0f) * x; + + auto mask = (x < 0.00349f); + return mask.thenElse(lo, hi); +} + static Sk4f clamp_0_to_255(const Sk4f& x) { // The order of the arguments is important here. We want to make sure that NaN // clamps to zero. Note that max(NaN, 0) = 0, while max(0, NaN) = NaN. @@ -134,12 +154,12 @@ static void color_xform_RGB1_2dot2_to_2dot2(uint32_t* dst, const uint32_t* src, static void color_xform_RGB1_srgb_to_srgb(uint32_t* dst, const uint32_t* src, int len, const float matrix[16]) { - color_xform_RGB1<sk_linear_from_srgb, sk_linear_to_srgb>(dst, src, len, matrix); + color_xform_RGB1<sk_linear_from_srgb, linear_to_srgb>(dst, src, len, matrix); } static void color_xform_RGB1_2dot2_to_srgb(uint32_t* dst, const uint32_t* src, int len, const float matrix[16]) { - color_xform_RGB1<sk_linear_from_2dot2, sk_linear_to_srgb>(dst, src, len, matrix); + color_xform_RGB1<sk_linear_from_2dot2, linear_to_srgb>(dst, src, len, matrix); } } // namespace SK_OPTS_NS |