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-rw-r--r--libglitter.h8
-rw-r--r--libglitter_colour_space_convert_rasters_double.c14
-rw-r--r--libglitter_get_colour_space_conversion_matrix_double.c48
3 files changed, 34 insertions, 36 deletions
diff --git a/libglitter.h b/libglitter.h
index 649d522..7e2a1ea 100644
--- a/libglitter.h
+++ b/libglitter.h
@@ -272,9 +272,11 @@ void libglitter_per_channel_desaturate_float(float **, size_t, size_t, size_t, s
* uses some other colour space, this function can output
* the conversion matrix for the CIE XYZ colour space,
* which can that be right-hand multiplied to get the
- * conversion matrix for some other colour
+ * conversion matrix for some other colour; but be aware
+ * that the output matrix is in column-major order, not
+ * row-major order
*
- * @param matrix Output buffer for the conversion matrix
+ * @param matrix Output buffer for the conversion matrix, in column-major order
* @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
@@ -329,7 +331,7 @@ void libglitter_get_colour_space_conversion_matrix_float(float[3][3], float, flo
* values per cell)
* @param width The horizontal number of pixels in the rasters
* @param height The vertical number of pixels in the rasters
- * @param matrix Colour space conversion matrix
+ * @param matrix Colour space conversion matrix, in column-major order
*/
void libglitter_colour_space_convert_rasters_double(size_t n, size_t m, double **, const double **,
size_t, size_t, size_t, size_t, size_t, size_t, const double[n][m]);
diff --git a/libglitter_colour_space_convert_rasters_double.c b/libglitter_colour_space_convert_rasters_double.c
index 7128998..3923911 100644
--- a/libglitter_colour_space_convert_rasters_double.c
+++ b/libglitter_colour_space_convert_rasters_double.c
@@ -6,9 +6,9 @@ static void
multiply_33(double **outputs, size_t opos, const double **inputs, size_t ipos, const double matrix[3][3])
{
double i0 = inputs[0][ipos], i1 = inputs[1][ipos], i2 = inputs[2][ipos];
- outputs[0][opos] = i0 * matrix[0][0] + i1 * matrix[1][0] + i2 * matrix[2][0];
- outputs[1][opos] = i0 * matrix[0][1] + i1 * matrix[1][1] + i2 * matrix[2][1];
- outputs[2][opos] = i0 * matrix[0][2] + i1 * matrix[1][2] + i2 * matrix[2][2];
+ outputs[0][opos] = i0 * matrix[0][0] + i1 * matrix[0][1] + i2 * matrix[0][2];
+ outputs[1][opos] = i0 * matrix[1][0] + i1 * matrix[1][1] + i2 * matrix[1][2];
+ outputs[2][opos] = i0 * matrix[2][0] + i1 * matrix[2][1] + i2 * matrix[2][2];
}
@@ -20,9 +20,9 @@ multiply_nn(size_t n, double **outputs, size_t opos, const double **inputs, size
for (j = 0; j < n; j++)
buffer[j] = inputs[j][ipos];
for (i = 0; i < n; i++) {
- outputs[i][opos] = buffer[0] * matrix[0][i];
+ outputs[i][opos] = buffer[0] * matrix[i][0];
for (j = 1; j < n; j++)
- outputs[i][opos] += buffer[j] * matrix[j][i];
+ outputs[i][opos] += buffer[j] * matrix[i][j];
}
}
@@ -35,9 +35,9 @@ multiply_nm(size_t n, size_t m, double **outputs /* m */, size_t opos, const dou
for (j = 0; j < n; j++)
buffer[j] = inputs[j][ipos];
for (i = 0; i < m; i++) {
- outputs[i][opos] = buffer[0] * matrix[0][i];
+ outputs[i][opos] = buffer[0] * matrix[i][0];
for (j = 1; j < n; j++)
- outputs[i][opos] += buffer[j] * matrix[j][i];
+ outputs[i][opos] += buffer[j] * matrix[i][j];
}
}
diff --git a/libglitter_get_colour_space_conversion_matrix_double.c b/libglitter_get_colour_space_conversion_matrix_double.c
index 3ee734d..e0f6aa1 100644
--- a/libglitter_get_colour_space_conversion_matrix_double.c
+++ b/libglitter_get_colour_space_conversion_matrix_double.c
@@ -12,12 +12,13 @@
/**
- * CIE XYZ-to-sRGB conversion matrix
+ * CIE XYZ-to-sRGB conversion matrix,
+ * in column-major order
*/
static const double srgb[3][3] = {
- { 3.240446254647737056586720427731, -1.537134761820080353089679192635, -0.498530193022728773666329971093},
- {-0.969266606244679751469561779231, 1.876011959788370209167851498933, 0.041556042214430065351304932619},
- { 0.055643503564352832235773149705, -0.204026179735960239147729566866, 1.057226567722703292062647051353}};
+ { 3.240446254647737056586720427731, -0.969266606244679751469561779231, 0.055643503564352832235773149705},
+ {-1.537134761820080353089679192635, 1.876011959788370209167851498933, -0.204026179735960239147729566866},
+ {-0.498530193022728773666329971093, 0.041556042214430065351304932619, 1.057226567722703292062647051353}};
#if defined(__GNUC__) && !defined(__clang__)
@@ -26,7 +27,7 @@ static const double srgb[3][3] = {
static void
-invert(double m[3][4])
+invert(double m[3][4]) /* row-major order */
{
double t;
size_t i;
@@ -55,7 +56,7 @@ libglitter_get_colour_space_conversion_matrix_double(double matrix[3][3], double
double y1, y2, y3;
double z1, z2, z3;
- /* Get colour space in CIE XYZ */
+ /* Get colour space in CIE XYZ (the matrix is in row-major order) */
mat[0][0] = x1 = X(c1x, c1y);
mat[0][1] = x2 = X(c2x, c2y);
mat[0][2] = x3 = X(c3x, c3y);
@@ -73,30 +74,25 @@ libglitter_get_colour_space_conversion_matrix_double(double matrix[3][3], double
y2 = mat[1][3];
y3 = mat[2][3];
- /* [[x1, x2, x3], [y1, y2, y3], [z1, z2, z3]] is
+ /* [x1, x2, x3; y1, y2, y3; z1, z2, z3] is
* the output RGB-to-CIE XYZ conversion matrix.
* If sRGB is desired, it is multiplied by the
* CIE XYZ-to-sRGB conversion matrix to get the
- * output RGB-to-sRGB conversion matrix. */
+ * output RGB-to-sRGB conversion matrix. The
+ * matrices are in column-major order. */
if (!xyz) {
- 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];
+ matrix[0][0] = x1 * srgb[0][0] + x2 * srgb[0][1] + x3 * srgb[0][2];
+ matrix[1][0] = x1 * srgb[1][0] + x2 * srgb[1][1] + x3 * srgb[1][2];
+ matrix[2][0] = x1 * srgb[2][0] + x2 * srgb[2][1] + x3 * srgb[2][2];
+ matrix[0][1] = y1 * srgb[0][0] + y2 * srgb[0][1] + y3 * srgb[0][2];
+ matrix[1][1] = y1 * srgb[1][0] + y2 * srgb[1][1] + y3 * srgb[1][2];
+ matrix[2][1] = y1 * srgb[2][0] + y2 * srgb[2][1] + y3 * srgb[2][2];
+ matrix[0][2] = z1 * srgb[0][0] + z2 * srgb[0][1] + z3 * srgb[0][2];
+ matrix[1][2] = z1 * srgb[1][0] + z2 * srgb[1][1] + z3 * srgb[1][2];
+ matrix[2][2] = z1 * srgb[2][0] + z2 * srgb[2][1] + z3 * srgb[2][2];
} else {
- matrix[0][0] = x1;
- matrix[0][1] = x2;
- matrix[0][2] = x3;
- matrix[1][0] = y1;
- matrix[1][1] = y2;
- matrix[1][2] = y3;
- matrix[2][0] = z1;
- matrix[2][1] = z2;
- matrix[2][2] = z3;
+ matrix[0][0] = x1, matrix[1][0] = x2, matrix[2][0] = x3;
+ matrix[0][1] = y1, matrix[1][1] = y2, matrix[2][1] = y3;
+ matrix[0][2] = z1, matrix[1][2] = z2, matrix[2][2] = z3;
}
}