diff options
| -rw-r--r-- | libdimension/color.c | 108 |
1 files changed, 54 insertions, 54 deletions
diff --git a/libdimension/color.c b/libdimension/color.c index f309d09..12edb20 100644 --- a/libdimension/color.c +++ b/libdimension/color.c @@ -192,35 +192,32 @@ static double dmnsn_sRGB_Cinv(double CsRGB) { } } +/* Perform the inverse linear sRGB conversion */ +static dmnsn_color +dmnsn_linear_color_from_sRGB(dmnsn_sRGB sRGB) +{ + dmnsn_color ret = { + .X = 0.4123808838268995*sRGB.R + 0.3575728355732478*sRGB.G + + 0.1804522977447919*sRGB.B, + .Y = 0.2126198631048975*sRGB.R + 0.7151387878413206*sRGB.G + + 0.0721499433963131*sRGB.B, + .Z = 0.0193434956789248*sRGB.R + 0.1192121694056356*sRGB.G + + 0.9505065664127130*sRGB.B, + .filter = 0.0, + .trans = 0.0 + }; + return ret; +} + /* Convert an sRGB value to a dmnsn_color */ dmnsn_color dmnsn_color_from_sRGB(dmnsn_sRGB sRGB) { - double Rlinear, Glinear, Blinear; /* Linear RGB values - no gamma */ - dmnsn_color ret; - - Rlinear = dmnsn_sRGB_Cinv(sRGB.R); - Glinear = dmnsn_sRGB_Cinv(sRGB.G); - Blinear = dmnsn_sRGB_Cinv(sRGB.B); - - /* - * Now, the linear conversion. Expressed as matrix multiplication, it looks - * like this: - * - * [X] [0.4124 0.3576 0.1805] [Rlinear] - * [Y] = [0.2126 0.7152 0.0722]*[Glinear] - * [X] [0.0193 0.1192 0.9505] [Blinear] - */ - ret.X = 0.4123808838268995*Rlinear + 0.3575728355732478*Glinear - + 0.1804522977447919*Blinear; - ret.Y = 0.2126198631048975*Rlinear + 0.7151387878413206*Glinear - + 0.0721499433963131*Blinear; - ret.Z = 0.0193434956789248*Rlinear + 0.1192121694056356*Glinear - + 0.9505065664127130*Blinear; - ret.filter = 0.0; - ret.trans = 0.0; + sRGB.R = dmnsn_sRGB_Cinv(sRGB.R); + sRGB.G = dmnsn_sRGB_Cinv(sRGB.G); + sRGB.B = dmnsn_sRGB_Cinv(sRGB.B); - return ret; + return dmnsn_linear_color_from_sRGB(sRGB); } /* Convert a dmnsn_color to a CIE XYZ color (actually a no-op) */ @@ -316,30 +313,29 @@ static double dmnsn_sRGB_C(double Clinear) { } } +/* Perform the linear sRGB conversion */ +static dmnsn_sRGB +dmnsn_linear_sRGB_from_color(dmnsn_color color) +{ + dmnsn_sRGB ret = { + .R = 3.2410*color.X - 1.5374*color.Y - 0.4986*color.Z, + .G = -0.9692*color.X + 1.8760*color.Y + 0.0416*color.Z, + .B = 0.0556*color.X - 0.2040*color.Y + 1.0570*color.Z + }; + return ret; +} + /* Convert a dmnsn_color to an sRGB color */ dmnsn_sRGB dmnsn_sRGB_from_color(dmnsn_color color) { - double Rlinear, Glinear, Blinear; /* Linear RGB values - no gamma */ - dmnsn_sRGB ret; + dmnsn_sRGB sRGB = dmnsn_linear_sRGB_from_color(color); - /* - * First, the linear conversion. Expressed as matrix multiplication, it looks - * like this: - * - * [Rlinear] [ 3.2410 -1.5374 -0.4986] [X] - * [Glinear] = [-0.9692 1.8760 0.0416]*[Y] - * [Blinear] [ 0.0556 -0.2040 1.0570] [Z] - */ - Rlinear = 3.2410*color.X - 1.5374*color.Y - 0.4986*color.Z; - Glinear = -0.9692*color.X + 1.8760*color.Y + 0.0416*color.Z; - Blinear = 0.0556*color.X - 0.2040*color.Y + 1.0570*color.Z; - - ret.R = dmnsn_sRGB_C(Rlinear); - ret.G = dmnsn_sRGB_C(Glinear); - ret.B = dmnsn_sRGB_C(Blinear); + sRGB.R = dmnsn_sRGB_C(sRGB.R); + sRGB.G = dmnsn_sRGB_C(sRGB.G); + sRGB.B = dmnsn_sRGB_C(sRGB.B); - return ret; + return sRGB; } /* Add two colors in a perceptually correct manner, using CIE L*a*b*. */ @@ -393,20 +389,24 @@ dmnsn_color_filter(dmnsn_color color, dmnsn_color filter) dmnsn_color dmnsn_color_illuminate(dmnsn_color light, dmnsn_color color) { - static dmnsn_CIE_RGB white = { 0.0 }; - if (!white.R) - white = dmnsn_RGB_from_color(dmnsn_white); - - dmnsn_CIE_RGB RGB1 = dmnsn_RGB_from_color(light); - dmnsn_CIE_RGB RGB2 = dmnsn_RGB_from_color(color); - - dmnsn_CIE_RGB RGB = { - .R = RGB1.R*RGB2.R/white.R, - .G = RGB1.G*RGB2.G/white.G, - .B = RGB1.B*RGB2.B/white.B + /* We use the sRGB primaries */ + dmnsn_sRGB sRGB1 = dmnsn_linear_sRGB_from_color(light), + sRGB2 = dmnsn_linear_sRGB_from_color(color); + + double R1 = 1.16*dmnsn_Lab_f(sRGB1.R) - 0.16, + R2 = 1.16*dmnsn_Lab_f(sRGB2.R) - 0.16, + G1 = 1.16*dmnsn_Lab_f(sRGB1.G) - 0.16, + G2 = 1.16*dmnsn_Lab_f(sRGB2.G) - 0.16, + B1 = 1.16*dmnsn_Lab_f(sRGB1.B) - 0.16, + B2 = 1.16*dmnsn_Lab_f(sRGB2.B) - 0.16; + + dmnsn_sRGB sRGB = { + .R = dmnsn_Lab_finv((R1*R2 + 0.16)/1.16), + .G = dmnsn_Lab_finv((G1*G2 + 0.16)/1.16), + .B = dmnsn_Lab_finv((B1*B2 + 0.16)/1.16) }; - dmnsn_color ret = dmnsn_color_from_RGB(RGB); + dmnsn_color ret = dmnsn_linear_color_from_sRGB(sRGB); ret.filter = color.filter; ret.trans = color.trans; |