diff options
| -rw-r--r-- | libdimension/canvas.c | 57 | ||||
| -rw-r--r-- | libdimension/dimension/canvas.h | 4 | ||||
| -rw-r--r-- | libdimension/dimension/color.h | 15 |
3 files changed, 44 insertions, 32 deletions
diff --git a/libdimension/canvas.c b/libdimension/canvas.c index c730b53..4e3f89f 100644 --- a/libdimension/canvas.c +++ b/libdimension/canvas.c @@ -27,10 +27,16 @@ dmnsn_pixel dmnsn_pixel_from_color(dmnsn_color color) { + double X, Y, Z; /* CIE XYZ values */ double Rlinear, Glinear, Blinear; /* Linear RGB values - no gamma */ double R, G, B; /* sRGB values */ dmnsn_pixel pixel; + /* Convert from CIE xyY to CIE XYZ */ + Y = color.Y; + X = Y*color.x/color.y; + Z = Y*(1.0 - color.x - color.y)/color.y; + /* * First, the linear conversion. Expressed as matrix multiplication, it looks * like this: @@ -39,9 +45,9 @@ dmnsn_pixel_from_color(dmnsn_color color) * [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; + Rlinear = 3.2410*X - 1.5374*Y - 0.4986*Z; + Glinear = -0.9692*X + 1.8760*Y + 0.0416*Z; + Blinear = 0.0556*X - 0.2040*Y + 1.0570*Z; /* * If C represents R, G, and B, then the sRGB values are now found as follows: @@ -71,41 +77,41 @@ dmnsn_pixel_from_color(dmnsn_color color) /* Now we go from unlimited to limited light, saturating at UINT16_MAX */ - if (R < 0) { - pixel.r = 0; - } else if (R > 1) { + if (R < 0.0) { + pixel.r = 0.0; + } else if (R > 1.0) { pixel.r = UINT16_MAX; } else { pixel.r = UINT16_MAX*R; } - if (G < 0) { - pixel.g = 0; - } else if (G > 1) { + if (G < 0.0) { + pixel.g = 0.0; + } else if (G > 1.0) { pixel.g = UINT16_MAX; } else { pixel.g = UINT16_MAX*G; } - if (B < 0) { - pixel.b = 0; - } else if (B > 1) { + if (B < 0.0) { + pixel.b = 0.0; + } else if (B > 1.0) { pixel.b = UINT16_MAX; } else { pixel.b = UINT16_MAX*B; } - if (color.alpha < 0) { - pixel.a = 0; - } else if (color.alpha > 1) { + if (color.filter < 0.0) { + pixel.a = 0.0; + } else if (color.filter > 1.0) { pixel.a = UINT16_MAX; } else { - pixel.a = UINT16_MAX*color.alpha; + pixel.a = UINT16_MAX*color.filter; } - if (color.trans < 0) { - pixel.t = 0; - } else if (color.trans > 1) { + if (color.trans < 0.0) { + pixel.t = 0.0; + } else if (color.trans > 1.0) { pixel.t = UINT16_MAX; } else { pixel.t = UINT16_MAX*color.trans; @@ -119,6 +125,7 @@ dmnsn_color_from_pixel(dmnsn_pixel pixel) { double R, G, B; /* sRGB values */ double Rlinear, Glinear, Blinear; /* Linear RGB values - no gamma */ + double X, Y, Z; /* CIE XYZ values */ dmnsn_color color; /* Conversion back to unlimited light */ @@ -162,11 +169,15 @@ dmnsn_color_from_pixel(dmnsn_pixel pixel) * [X] [0.0193 0.1192 0.9505] [Blinear] */ - color.X = 0.4124*Rlinear + 0.3576*Glinear + 0.1805*Blinear; - color.Y = 0.2126*Rlinear + 0.7152*Glinear + 0.0722*Blinear; - color.Z = 0.0193*Rlinear + 0.1192*Glinear + 0.9505*Blinear; + X = 0.4124*Rlinear + 0.3576*Glinear + 0.1805*Blinear; + Y = 0.2126*Rlinear + 0.7152*Glinear + 0.0722*Blinear; + Z = 0.0193*Rlinear + 0.1192*Glinear + 0.9505*Blinear; - color.alpha = ((double)pixel.a)/UINT16_MAX; + /* Now convert to CIE xyY colorspace */ + color.x = X/(X + Y + Z); + color.y = Y/(X + Y + Z); + color.Y = Y; + color.filter = ((double)pixel.a)/UINT16_MAX; color.trans = ((double)pixel.t)/UINT16_MAX; return color; diff --git a/libdimension/dimension/canvas.h b/libdimension/dimension/canvas.h index 251c64a..8959e12 100644 --- a/libdimension/dimension/canvas.h +++ b/libdimension/dimension/canvas.h @@ -27,8 +27,8 @@ /* 48-bit sRGB color for pixels. */ typedef struct { - uint16_t r, g, b; - uint16_t a, t; + uint16_t r, g, b; /* Red, green, blue */ + uint16_t a, t; /* Filtered transparancy, normal transparancy */ } dmnsn_pixel; dmnsn_pixel dmnsn_pixel_from_color(dmnsn_color color); diff --git a/libdimension/dimension/color.h b/libdimension/dimension/color.h index 1f4a42e..34668e3 100644 --- a/libdimension/dimension/color.h +++ b/libdimension/dimension/color.h @@ -29,14 +29,15 @@ extern "C" { #endif -/* CIE 1931 XYZ color. */ +/* CIE 1931 xyY color. */ typedef struct { - double X, Y, Z; /* X, Y, and Z are the tristimulus values of a color in CIE - 1931 XYZ color space. We use an unlimited light model - here, where the range of X, Y, and Z are unbounded >= 0. */ - double alpha, trans; /* Alpha transparancy only lets light of this color - through; regular transparancy lets all colors - through */ + double x, y, Y; /* x and y are chromaticity coordinates, and Y is luminance, + in the CIE 1931 xyZ color space. We use an unlimited light + model, so x,y in [0, 1] and Y >= 0, with 1 = diffuse + white */ + double filter, trans; /* Filter transparancy only lets light of this color + through; regular transparancy lets all colors + through */ } dmnsn_color; #ifdef __cplusplus |