diff options
| -rw-r--r-- | Makefile | 2 | ||||
| -rw-r--r-- | libglitter.h | 42 | ||||
| -rw-r--r-- | libglitter_get_colour_space_conversion_matrix_double.c | 90 | ||||
| -rw-r--r-- | libglitter_get_colour_space_conversion_matrix_float.c | 25 |
4 files changed, 159 insertions, 0 deletions
@@ -27,6 +27,8 @@ OBJ =\ libglitter_desaturate_float.o\ libglitter_create_render_context.o\ libglitter_free_render_context.o\ + libglitter_get_colour_space_conversion_matrix_double.o\ + libglitter_get_colour_space_conversion_matrix_float.o\ libglitter_update_render_context.o HDR =\ diff --git a/libglitter.h b/libglitter.h index 0fc5888..4cd64bf 100644 --- a/libglitter.h +++ b/libglitter.h @@ -7,6 +7,14 @@ /** + * The CIE xyY values of the D65 illuminant + */ +#define LIBGLITTER_ILLUMINANT_D65\ + 0.312726871026564878786047074755,\ + 0.329023206641284038376227272238, 1.0\ + + +/** * Rendering context for an input raster's specifications * * Render context's are thread-safe, however updating them are not @@ -183,4 +191,38 @@ void libglitter_desaturate_double(double **, size_t, size_t, size_t, size_t, siz void libglitter_desaturate_float(float **, size_t, size_t, size_t, size_t, size_t, float, const float *); +/** + * Get the matrix each pixel shall be multiplied with + * to convert it from the output's colour space to sRGB + * + * This is useful when the output does not use sRGB, + * but the application does + * + * @param matrix Output buffer for the conversion matrix + * @param c1x The CIE x value (as in CIE xyY) of the output's first primary colour + * @param c1y The CIE y value (as in CIE xyY) of the output's first primary colour + * @param c2x The CIE x value (as in CIE xyY) of the output's second primary colour + * @param c2y The CIE y value (as in CIE xyY) of the output's second primary colour + * @param c3x The CIE x value (as in CIE xyY) of the output's third primary colour + * @param c3y The CIE y value (as in CIE xyY) of the output's third primary colour + * @param white_x The CIE x value (as in CIE xyY) of the output's white point + * @param white_y The CIE y value (as in CIE xyY) of the output's white point + * @param white_Y The CIE Y value (as in CIE xyY) of the output's white point + * + * `LIBGLITTER_ILLUMINANT_D65` can be input in place of + * `white_x, white_y, white_Y` (it expands to three arguments) + * if the output's whitepoint is the D65 illuminant + */ +void libglitter_get_colour_space_conversion_matrix_double(double[3][3], double, double, double, double, + double, double, double, double, double); + +/** + * This value is identical to `libglitter_get_colour_space_conversion_matrix_double`, + * apart from it parameter types, see `libglitter_get_colour_space_conversion_matrix_double` + * for details about this function + */ +void libglitter_get_colour_space_conversion_matrix_float(float[3][3], float, float, float, float, + float, float, float, float, float); + + #endif 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]; +} diff --git a/libglitter_get_colour_space_conversion_matrix_float.c b/libglitter_get_colour_space_conversion_matrix_float.c new file mode 100644 index 0000000..022c2a4 --- /dev/null +++ b/libglitter_get_colour_space_conversion_matrix_float.c @@ -0,0 +1,25 @@ +/* See LICENSE file for copyright and license details. */ +#include "common.h" + + +void +libglitter_get_colour_space_conversion_matrix_float(float matrix[3][3], float c1x, float c1y, + float c2x, float c2y, float c3x, float c3y, + float white_x, float white_y, float white_Y) +{ + double double_matrix[3][3]; + libglitter_get_colour_space_conversion_matrix_double(double_matrix, + (double)c1x, (double)c1y, + (double)c2x, (double)c2y, + (double)c3x, (double)c3y, + (double)white_x, (double)white_y, (double)white_Y); + matrix[0][0] = (float)double_matrix[0][0]; + matrix[0][1] = (float)double_matrix[0][1]; + matrix[0][2] = (float)double_matrix[0][2]; + matrix[1][0] = (float)double_matrix[1][0]; + matrix[1][1] = (float)double_matrix[1][1]; + matrix[1][2] = (float)double_matrix[1][2]; + matrix[2][0] = (float)double_matrix[2][0]; + matrix[2][1] = (float)double_matrix[2][1]; + matrix[2][2] = (float)double_matrix[2][2]; +} |