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Diffstat (limited to '')
| -rw-r--r-- | libglitter_get_colour_space_conversion_matrix_double.c | 90 |
1 files changed, 90 insertions, 0 deletions
diff --git a/libglitter_get_colour_space_conversion_matrix_double.c b/libglitter_get_colour_space_conversion_matrix_double.c new file mode 100644 index 0000000..fd3ecbc --- /dev/null +++ b/libglitter_get_colour_space_conversion_matrix_double.c @@ -0,0 +1,90 @@ +/* See LICENSE file for copyright and license details. */ +#include "common.h" + +#define X(x, y) ((x) / (y)) +#define Z(x, y) ((1 - (x)) / (y) - 1) + + +#if defined(__GNUC__) && !defined(__clang__) +# pragma GCC diagnostic push +# pragma GCC diagnostic ignored "-Wunsuffixed-float-constants" +#endif + + +/** + * CIE XYZ-to-sRGB conversion matrix + */ +static const double srgb[3][3] = { + { 3.240446254647737056586720427731, -1.537134761820080353089679192635, -0.498530193022728773666329971093}, + {-0.969266606244679751469561779231, 1.876011959788370209167851498933, 0.041556042214430065351304932619}, + { 0.055643503564352832235773149705, -0.204026179735960239147729566866, 1.057226567722703292062647051353}}; + + +#if defined(__GNUC__) && !defined(__clang__) +# pragma GCC diagnostic pop +#endif + + +static void +invert(double m[3][4]) +{ + double t; + size_t i; + + /* Set m[0][0] = 1 */ for (t = m[0][0], i = 0; i < 4; i++) m[0][i] /= t; + /* Set m[1][0] = 0 */ for (t = m[1][0], i = 0; i < 4; i++) m[1][i] -= t * m[0][i]; + /* Set m[2][0] = 0 */ for (t = m[2][0], i = 0; i < 4; i++) m[2][i] -= t * m[0][i]; + + /* Set m[1][1] = 1 */ for (t = m[1][1], i = 1; i < 4; i++) m[1][i] /= t; + /* Set m[2][1] = 0 */ for (t = m[2][1], i = 1; i < 4; i++) m[2][i] -= t * m[1][i]; + /* Set m[0][1] = 0 */ for (t = m[0][1], i = 1; i < 4; i++) m[0][i] -= t * m[1][i]; + + /* Set m[2][2] = 1 */ for (t = m[2][2], i = 2; i < 4; i++) m[2][i] /= t; + /* Set m[1][2] = 0 */ for (t = m[1][2], i = 2; i < 4; i++) m[1][i] -= t * m[2][i]; + /* Set m[0][2] = 0 */ for (t = m[0][2], i = 2; i < 4; i++) m[0][i] -= t * m[2][i]; +} + + +void +libglitter_get_colour_space_conversion_matrix_double(double matrix[3][3], double c1x, double c1y, + double c2x, double c2y, double c3x, double c3y, + double white_x, double white_y, double white_Y) +{ + double mat[3][4]; + double x1, x2, x3; + double y1, y2, y3; + double z1, z2, z3; + + /* Get colour space in CIE XYZ */ + mat[0][0] = x1 = X(c1x, c1y); + mat[0][1] = x2 = X(c2x, c2y); + mat[0][2] = x3 = X(c3x, c3y); + mat[1][3] = X(white_x, white_y) * white_Y; + mat[1][0] = 1; + mat[1][1] = 1; + mat[1][2] = 1; + mat[1][3] = white_Y; + mat[2][0] = z1 = Z(c1x, c1y); + mat[2][1] = z2 = Z(c2x, c2y); + mat[2][2] = z3 = Z(c3x, c3y); + mat[2][3] = Z(white_x, white_y) * white_Y; + invert(mat); + y1 = mat[0][3]; + y2 = mat[1][3]; + y3 = mat[2][3]; + + /* [[x1, x2, x3], [y1, y2, y3], [z1, z2, z3]] is + * the output RGB-to-CIE XYZ conversion matrix. It + * is multiplied by the CIE XYZ-to-sRGB conversion + * matrix to get the output RGB-to-sRGB conversion + * matrix. */ + matrix[0][0] = x1 * srgb[0][0] + x2 * srgb[1][0] + x3 * srgb[2][0]; + matrix[0][1] = x1 * srgb[0][1] + x2 * srgb[1][1] + x3 * srgb[2][1]; + matrix[0][2] = x1 * srgb[0][2] + x2 * srgb[1][2] + x3 * srgb[2][2]; + matrix[1][0] = y1 * srgb[0][0] + y2 * srgb[1][0] + y3 * srgb[2][0]; + matrix[1][1] = y1 * srgb[0][1] + y2 * srgb[1][1] + y3 * srgb[2][1]; + matrix[1][2] = y1 * srgb[0][2] + y2 * srgb[1][2] + y3 * srgb[2][2]; + matrix[2][0] = z1 * srgb[0][0] + z2 * srgb[1][0] + z3 * srgb[2][0]; + matrix[2][1] = z1 * srgb[0][1] + z2 * srgb[1][1] + z3 * srgb[2][1]; + matrix[2][2] = z1 * srgb[0][2] + z2 * srgb[1][2] + z3 * srgb[2][2]; +} |