Add a white balance effect (port of my white balance effect from Frei0r).

diff --git a/Makefile b/Makefile
index 21e76aacf4342f52973096c83dd7ee3984568e16..028b8555e5952fb38733feb66762a8dc7e6e00c6 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -12,6 +12,7 @@ OBJS += ycbcr_input.o
 
 # Effects.
 OBJS += lift_gamma_gain_effect.o
 
 # Effects.
 OBJS += lift_gamma_gain_effect.o

+OBJS += white_balance_effect.o

 OBJS += gamma_expansion_effect.o
 OBJS += gamma_compression_effect.o
 OBJS += colorspace_conversion_effect.o
 OBJS += gamma_expansion_effect.o
 OBJS += gamma_compression_effect.o
 OBJS += colorspace_conversion_effect.o

diff --git a/effect.cpp b/effect.cpp
index d0222dec91f936e662d5c82adb1c05ccf0eb4110..74bd939f3f1e811303519e4aaf5d5ed2dac615bb 100644 (file)
--- a/effect.cpp
+++ b/effect.cpp
@@ -79,6 +79,24 @@ void set_uniform_vec4_array(GLuint glsl_program_num, const std::string &prefix,
        check_error();
 }
 
        check_error();
 }
 

+void set_uniform_mat3(GLuint glsl_program_num, const std::string &prefix, const std::string &key, const Matrix3x3 matrix)
+{
+       GLint location = get_uniform_location(glsl_program_num, prefix, key);
+       if (location == -1) {
+               return;
+       }
+       check_error();
+
+       // Convert to float (GLSL has no double matrices).
+       float matrixf[9];
+       for (unsigned i = 0; i < 9; ++i) {
+               matrixf[i] = matrix[i];
+       }
+
+       glUniformMatrix3fv(location, 1, GL_FALSE, matrixf);
+       check_error();
+}
+

 bool Effect::set_int(const std::string &key, int value)
 {
        if (params_int.count(key) == 0) {
 bool Effect::set_int(const std::string &key, int value)
 {
        if (params_int.count(key) == 0) {

diff --git a/effect.h b/effect.h
index ef58392715ea7ade816bfc440c1eec65bd3ee410..dee562413f21498525cd83a3cdc43f5f36261996 100644 (file)
--- a/effect.h
+++ b/effect.h
@@ -17,6 +17,7 @@
 #include <assert.h>
 
 #include "opengl.h"
 #include <assert.h>
 
 #include "opengl.h"

+#include "util.h"

 
 class EffectChain;
 class Node;
 
 class EffectChain;
 class Node;


@@ -45,6 +46,7 @@ void set_uniform_float_array(GLuint glsl_program_num, const std::string &prefix,
 void set_uniform_vec2(GLuint glsl_program_num, const std::string &prefix, const std::string &key, const float *values);
 void set_uniform_vec3(GLuint glsl_program_num, const std::string &prefix, const std::string &key, const float *values);
 void set_uniform_vec4_array(GLuint glsl_program_num, const std::string &prefix, const std::string &key, const float *values, size_t num_values);
 void set_uniform_vec2(GLuint glsl_program_num, const std::string &prefix, const std::string &key, const float *values);
 void set_uniform_vec3(GLuint glsl_program_num, const std::string &prefix, const std::string &key, const float *values);
 void set_uniform_vec4_array(GLuint glsl_program_num, const std::string &prefix, const std::string &key, const float *values, size_t num_values);

+void set_uniform_mat3(GLuint glsl_program_num, const std::string &prefix, const std::string &key, const Matrix3x3 matrix);

 
 class Effect {
 public:
 
 class Effect {
 public:

diff --git a/util.cpp b/util.cpp
index 8dcf219b3ee6be7cd8592f26268eefb33bae3fcb..08298c7701b9146fcbd76b9330170b458a80f28b 100644 (file)
--- a/util.cpp
+++ b/util.cpp
@@ -99,6 +99,13 @@ void multiply_3x3_matrices(const Matrix3x3 a, const Matrix3x3 b, Matrix3x3 resul
         result[8] = a[2] * b[6] + a[5] * b[7] + a[8] * b[8];
 }
 
         result[8] = a[2] * b[6] + a[5] * b[7] + a[8] * b[8];
 }
 

+void multiply_3x3_matrix_float3(const Matrix3x3 M, float x0, float x1, float x2, float *y0, float *y1, float *y2)
+{
+       *y0 = M[0] * x0 + M[3] * x1 + M[6] * x2;
+       *y1 = M[1] * x0 + M[4] * x1 + M[7] * x2;
+       *y2 = M[2] * x0 + M[5] * x1 + M[8] * x2;
+}
+

 void invert_3x3_matrix(const Matrix3x3 m, Matrix3x3 result)
 {
        double inv_det = 1.0 / (
 void invert_3x3_matrix(const Matrix3x3 m, Matrix3x3 result)
 {
        double inv_det = 1.0 / (

diff --git a/util.h b/util.h
index 209a7dca42958a9313ed3f5d441267d9000e187a..da2bf50b1283a1060020c47f33b2e20c50bd65fc 100644 (file)
--- a/util.h
+++ b/util.h
@@ -29,6 +29,9 @@ GLuint compile_shader(const std::string &shader_src, GLenum type);
 // Compute a * b.
 void multiply_3x3_matrices(const Matrix3x3 a, const Matrix3x3 b, Matrix3x3 result);
 
 // Compute a * b.
 void multiply_3x3_matrices(const Matrix3x3 a, const Matrix3x3 b, Matrix3x3 result);
 

+// Compute M * [x0 x1 x2]'.
+void multiply_3x3_matrix_float3(const Matrix3x3 M, float x0, float x1, float x2, float *y0, float *y1, float *y2);
+

 // Compute m^-1. Result is undefined if the matrix is singular or near-singular.
 void invert_3x3_matrix(const Matrix3x3 m, Matrix3x3 result);
 
 // Compute m^-1. Result is undefined if the matrix is singular or near-singular.
 void invert_3x3_matrix(const Matrix3x3 m, Matrix3x3 result);
 

diff --git a/white_balance_effect.cpp b/white_balance_effect.cpp
new file mode 100644 (file)
index 0000000..4c24cd2
--- /dev/null
+++ b/white_balance_effect.cpp
@@ -0,0 +1,153 @@
+#include <math.h>
+#include <assert.h>
+
+#include "white_balance_effect.h"
+#include "util.h"
+#include "opengl.h"
+
+namespace {
+
+// Temperature is in Kelvin. Formula from http://en.wikipedia.org/wiki/Planckian_locus#Approximation .
+void convert_color_temperature_to_xyz(float T, float *x, float *y, float *z)
+{
+       double invT = 1.0 / T;
+       double xc, yc;
+
+       assert(T >= 1000.0f);
+       assert(T <= 15000.0f);
+
+       if (T <= 4000.0f) {
+               xc = ((-0.2661239e9 * invT - 0.2343580e6) * invT + 0.8776956e3) * invT + 0.179910;
+       } else {
+               xc = ((-3.0258469e9 * invT + 2.1070379e6) * invT + 0.2226347e3) * invT + 0.240390;
+       }
+
+       if (T <= 2222.0f) {
+               yc = ((-1.1063814 * xc - 1.34811020) * xc + 2.18555832) * xc - 0.20219683;
+       } else if (T <= 4000.0f) {
+               yc = ((-0.9549476 * xc - 1.37418593) * xc + 2.09137015) * xc - 0.16748867;
+       } else {
+               yc = (( 3.0817580 * xc - 5.87338670) * xc + 3.75112997) * xc - 0.37001483;
+       }
+
+       *x = xc;
+       *y = yc;
+       *z = 1.0 - xc - yc;
+}
+
+// Assuming sRGB primaries, from Wikipedia.
+static const Matrix3x3 rgb_to_xyz_matrix = {
+       0.4124, 0.2126, 0.0193, 
+       0.3576, 0.7152, 0.1192,
+       0.1805, 0.0722, 0.9505,
+};
+
+/*
+ * There are several different LMS spaces, at least according to Wikipedia.
+ * Through practical testing, I've found most of them (like the CIECAM02 model)
+ * to yield a result that is too reddish in practice, possibly because they
+ * are intended for different illuminants than what sRGB assumes. 
+ *
+ * This is the RLAB space, normalized to D65, which means that the standard
+ * D65 illuminant (x=0.31271, y=0.32902, z=1-y-x) gives L=M=S under this transformation.
+ * This makes sense because sRGB (which is used to derive those XYZ values
+ * in the first place) assumes the D65 illuminant, and so the D65 illuminant
+ * also gives R=G=B in sRGB.
+ */
+static const Matrix3x3 xyz_to_lms_matrix = {
+        0.4002, -0.2263,    0.0,
+        0.7076,  1.1653,    0.0,
+       -0.0808,  0.0457, 0.9182,
+};
+
+/*
+ * For a given reference color (given in XYZ space),
+ * compute scaling factors for L, M and S. What we want at the output is equal L, M and S
+ * for the reference color (making it a neutral illuminant), or sL ref_L = sM ref_M = sS ref_S.
+ * This removes two degrees of freedom for our system, and we only need to find fL.
+ *
+ * A reasonable last constraint would be to preserve Y, approximately the brightness,
+ * for the reference color. Since L'=M'=S' and the Y row of the LMS-to-XYZ matrix
+ * sums to unity, we know that Y'=L', and it's easy to find the fL that sets Y'=Y.
+ */
+static void compute_lms_scaling_factors(float x, float y, float z, float *scale_l, float *scale_m, float *scale_s)
+{
+       Matrix3x3 xyz_to_rgb_matrix;
+       invert_3x3_matrix(rgb_to_xyz_matrix, xyz_to_rgb_matrix);
+
+       float l, m, s;
+       multiply_3x3_matrix_float3(xyz_to_rgb_matrix, x, y, z, &l, &m, &s);
+
+       *scale_l = y / l;
+       *scale_m = *scale_l * (l / m);
+       *scale_s = *scale_l * (l / s);
+}
+
+}  // namespace
+
+WhiteBalanceEffect::WhiteBalanceEffect()
+       : neutral_color(0.5f, 0.5f, 0.5f),
+         output_color_temperature(6500.0f)
+{
+       register_vec3("neutral_color", (float *)&neutral_color);
+       register_float("output_color_temperature", &output_color_temperature);
+}
+
+std::string WhiteBalanceEffect::output_fragment_shader()
+{
+       return read_file("white_balance_effect.frag");
+}
+
+void WhiteBalanceEffect::set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num)
+{
+       float x, y, z;
+       multiply_3x3_matrix_float3(rgb_to_xyz_matrix, neutral_color.r, neutral_color.g, neutral_color.b, &x, &y, &z);
+
+       float l, m, s;
+       multiply_3x3_matrix_float3(xyz_to_lms_matrix, x, y, z, &l, &m, &s);
+
+       float l_scale, m_scale, s_scale;
+       compute_lms_scaling_factors(x, y, z, &l_scale, &m_scale, &s_scale);
+
+       /*
+        * Now apply the color balance. Simply put, we find the chromacity point
+        * for the desired white temperature, see what LMS scaling factors they
+        * would have given us, and then reverse that transform. For T=6500K,
+        * the default, this gives us nearly an identity transform (but only nearly,
+        * since the D65 illuminant does not exactly match the results of T=6500K);
+        * we normalize so that T=6500K really is a no-op.
+        */
+       float white_x, white_y, white_z, l_scale_white, m_scale_white, s_scale_white;
+       convert_color_temperature_to_xyz(output_color_temperature, &white_x, &white_y, &white_z);
+       compute_lms_scaling_factors(white_x, white_y, white_z, &l_scale_white, &m_scale_white, &s_scale_white);
+       
+       float ref_x, ref_y, ref_z, l_scale_ref, m_scale_ref, s_scale_ref;
+       convert_color_temperature_to_xyz(6500.0f, &ref_x, &ref_y, &ref_z);
+       compute_lms_scaling_factors(ref_x, ref_y, ref_z, &l_scale_ref, &m_scale_ref, &s_scale_ref);
+       
+       l_scale *= l_scale_ref / l_scale_white;
+       m_scale *= m_scale_ref / m_scale_white;
+       s_scale *= s_scale_ref / s_scale_white;
+       
+       /*
+        * Concatenate all the different linear operations into a single 3x3 matrix.
+        * Note that since we postmultiply our vectors, the order of the matrices
+        * has to be the opposite of the execution order.
+        */
+       Matrix3x3 lms_to_xyz_matrix, xyz_to_rgb_matrix;
+       invert_3x3_matrix(xyz_to_lms_matrix, lms_to_xyz_matrix);
+       invert_3x3_matrix(rgb_to_xyz_matrix, xyz_to_rgb_matrix);
+
+       Matrix3x3 temp, temp2, corr_matrix;
+       Matrix3x3 lms_scale_matrix = {
+               l_scale,    0.0f,    0.0f,
+                  0.0f, m_scale,    0.0f,
+                  0.0f,    0.0f, s_scale,
+       };
+       multiply_3x3_matrices(xyz_to_rgb_matrix, lms_to_xyz_matrix, temp);
+       multiply_3x3_matrices(temp, lms_scale_matrix, temp2);
+       multiply_3x3_matrices(temp2, xyz_to_lms_matrix, temp);
+       multiply_3x3_matrices(temp, rgb_to_xyz_matrix, corr_matrix);
+
+       set_uniform_mat3(glsl_program_num, prefix, "correction_matrix", corr_matrix);
+}

diff --git a/white_balance_effect.frag b/white_balance_effect.frag
new file mode 100644 (file)
index 0000000..926e0de
--- /dev/null
+++ b/white_balance_effect.frag
@@ -0,0 +1,7 @@
+uniform mat3 PREFIX(correction_matrix);
+
+vec4 FUNCNAME(vec2 tc) {
+       vec4 ret = INPUT(tc);
+       ret.rgb = PREFIX(correction_matrix) * ret.rgb;
+       return ret;
+}

diff --git a/white_balance_effect.h b/white_balance_effect.h
new file mode 100644 (file)
index 0000000..80416cb
--- /dev/null
+++ b/white_balance_effect.h
@@ -0,0 +1,25 @@
+#ifndef _WHITE_BALANCE_EFFECT_H
+#define _WHITE_BALANCE_EFFECT_H 1
+
+// Color correction in LMS color space.
+
+#include "effect.h"
+
+class WhiteBalanceEffect : public Effect {
+public:
+       WhiteBalanceEffect();
+       virtual std::string effect_type_id() const { return "WhiteBalanceEffect"; }
+       std::string output_fragment_shader();
+
+       void set_gl_state(GLuint glsl_program_num, const std::string &prefix, unsigned *sampler_num);
+
+private:
+       // The neutral color, in linear sRGB.
+       RGBTriplet neutral_color;
+
+       // Output color temperature (in Kelvins).
+       // Choosing 6500 will lead to no color cast (ie., the neutral color becomes perfectly gray).
+       float output_color_temperature;
+};
+
+#endif // !defined(_WHITE_BALANCE_EFFECT_H)