Color management: add OCIO aware utility functions for transform to/from XYZ.

intern/opencolorio/fallback_impl.cc

@@ -333,6 +333,13 @@ void FallbackImpl::configGetDefaultLumaCoefs(OCIO_ConstConfigRcPtr * /*config*/,
 	rgb[2] = 0.0722f;
 }
 
+void FallbackImpl::configGetXYZtoRGB(OCIO_ConstConfigRcPtr * /*config*/,
+                                     float xyz_to_rgb[3][3])
+{
+	/* Default to ITU-BT.709. */
+	memcpy(xyz_to_rgb, OCIO_XYZ_TO_LINEAR_SRGB, sizeof(OCIO_XYZ_TO_LINEAR_SRGB));
+}
+
 int FallbackImpl::configGetNumLooks(OCIO_ConstConfigRcPtr * /*config*/)
 {
 	return 0;

intern/opencolorio/ocio_capi.cc

@@ -137,6 +137,11 @@ void OCIO_configGetDefaultLumaCoefs(OCIO_ConstConfigRcPtr *config, float *rgb)
 	impl->configGetDefaultLumaCoefs(config, rgb);
 }
 
+void OCIO_configGetXYZtoRGB(OCIO_ConstConfigRcPtr *config, float xyz_to_rgb[3][3])
+{
+	impl->configGetXYZtoRGB(config, xyz_to_rgb);
+}
+
 int OCIO_configGetNumLooks(OCIO_ConstConfigRcPtr *config)
 {
 	return impl->configGetNumLooks(config);

intern/opencolorio/ocio_capi.h

@@ -54,6 +54,13 @@ OCIO_DECLARE_HANDLE(OCIO_ExponentTransformRcPtr);
 OCIO_DECLARE_HANDLE(OCIO_MatrixTransformRcPtr);
 OCIO_DECLARE_HANDLE(OCIO_ConstLookRcPtr);
 
+/* Standard XYZ to linear sRGB transform, for fallback. */
+static const float OCIO_XYZ_TO_LINEAR_SRGB[3][3] = {
+	{3.2404542f, -0.9692660f, 0.0556434f},
+	{-1.5371385f, 1.8760108f, -0.2040259f},
+	{-0.4985314f, 0.0415560f, 1.0572252f}};
+
+
 /* This structure is used to pass curve mapping settings from
  * blender's DNA structure stored in view transform settings
  * to a generic OpenColorIO C-API.
@@ -141,6 +148,7 @@ const char *OCIO_configGetView(OCIO_ConstConfigRcPtr *config, const char *displa
 const char *OCIO_configGetDisplayColorSpaceName(OCIO_ConstConfigRcPtr *config, const char *display, const char *view);
 
 void        OCIO_configGetDefaultLumaCoefs(OCIO_ConstConfigRcPtr *config, float *rgb);
+void        OCIO_configGetXYZtoRGB(OCIO_ConstConfigRcPtr *config, float xyz_to_rgb[3][3]);
 
 int                  OCIO_configGetNumLooks(OCIO_ConstConfigRcPtr *config);
 const char          *OCIO_configGetLookNameByIndex(OCIO_ConstConfigRcPtr *config, int index);

intern/opencolorio/ocio_impl.cc

@@ -419,6 +419,33 @@ void OCIOImpl::configGetDefaultLumaCoefs(OCIO_ConstConfigRcPtr *config, float *r
 	}
 }
 
+void OCIOImpl::configGetXYZtoRGB(OCIO_ConstConfigRcPtr *config_, float xyz_to_rgb[3][3])
+{
+	ConstConfigRcPtr config = (*(ConstConfigRcPtr *) config_);
+
+	/* Default to ITU-BT.709 in case no appropriate transform found. */
+	memcpy(xyz_to_rgb, OCIO_XYZ_TO_LINEAR_SRGB, sizeof(OCIO_XYZ_TO_LINEAR_SRGB));
+
+	/* Auto estimate from XYZ and scene_linear roles, assumed to be a linear transform. */
+	if(config->hasRole("XYZ") && config->hasRole("scene_linear")) {
+		ConstProcessorRcPtr to_rgb_processor = config->getProcessor("XYZ", "scene_linear");
+		if(to_rgb_processor) {
+			xyz_to_rgb[0][0] = 1.0f;
+			xyz_to_rgb[0][1] = 0.0f;
+			xyz_to_rgb[0][2] = 0.0f;
+			xyz_to_rgb[1][0] = 0.0f;
+			xyz_to_rgb[1][1] = 1.0f;
+			xyz_to_rgb[1][2] = 0.0f;
+			xyz_to_rgb[2][0] = 0.0f;
+			xyz_to_rgb[2][1] = 0.0f;
+			xyz_to_rgb[2][2] = 1.0f;
+			to_rgb_processor->applyRGB(xyz_to_rgb[0]);
+			to_rgb_processor->applyRGB(xyz_to_rgb[1]);
+			to_rgb_processor->applyRGB(xyz_to_rgb[2]);
+		}
+	}
+}
+
 int OCIOImpl::configGetNumLooks(OCIO_ConstConfigRcPtr *config)
 {
 	try {

intern/opencolorio/ocio_impl.h

@@ -59,6 +59,7 @@ public:
 	virtual const char *configGetDisplayColorSpaceName(OCIO_ConstConfigRcPtr *config, const char *display, const char *view) = 0;
 
 	virtual void configGetDefaultLumaCoefs(OCIO_ConstConfigRcPtr *config, float *rgb) = 0;
+	virtual void configGetXYZtoRGB(OCIO_ConstConfigRcPtr *config, float xyz_to_rgb[3][3]) = 0;
 
 	virtual int                  configGetNumLooks(OCIO_ConstConfigRcPtr *config) = 0;
 	virtual const char          *configGetLookNameByIndex(OCIO_ConstConfigRcPtr *config, int index) = 0;
@@ -148,6 +149,7 @@ public:
 	const char *configGetDisplayColorSpaceName(OCIO_ConstConfigRcPtr *config, const char *display, const char *view);
 
 	void configGetDefaultLumaCoefs(OCIO_ConstConfigRcPtr *config, float *rgb);
+	void configGetXYZtoRGB(OCIO_ConstConfigRcPtr *config, float xyz_to_rgb[3][3]);
 
 	int                  configGetNumLooks(OCIO_ConstConfigRcPtr *config);
 	const char          *configGetLookNameByIndex(OCIO_ConstConfigRcPtr *config, int index);
@@ -238,6 +240,7 @@ public:
 	const char *configGetDisplayColorSpaceName(OCIO_ConstConfigRcPtr *config, const char *display, const char *view);
 
 	void configGetDefaultLumaCoefs(OCIO_ConstConfigRcPtr *config, float *rgb);
+	void configGetXYZtoRGB(OCIO_ConstConfigRcPtr *config, float xyz_to_rgb[3][3]);
 
 	int                  configGetNumLooks(OCIO_ConstConfigRcPtr *config);
 	const char          *configGetLookNameByIndex(OCIO_ConstConfigRcPtr *config, int index);

source/blender/blenlib/BLI_math_color.h

@@ -64,7 +64,6 @@ void hsl_to_rgb_v(const float hcl[3], float r_rgb[3]);
 void hex_to_rgb(char *hexcol, float *r, float *g, float *b);
 void yuv_to_rgb(float y, float u, float v, float *lr, float *lg, float *lb, int colorspace);
 void ycc_to_rgb(float y, float cb, float cr, float *lr, float *lg, float *lb, int colorspace);
-void xyz_to_rgb(float x, float y, float z, float *r, float *g, float *b, int colorspace);
 void cpack_to_rgb(unsigned int col, float *r, float *g, float *b);
 
 /***************** Conversion from RGB ********************/
@@ -79,8 +78,6 @@ void rgb_to_hsl_compat(float r, float g, float b, float *lh, float *ls, float *l
 void rgb_to_hsl_compat_v(const float rgb[3], float r_hsl[3]);
 void rgb_to_hsv_compat(float r, float g, float b, float *lh, float *ls, float *lv);
 void rgb_to_hsv_compat_v(const float rgb[3], float r_hsv[3]);
-void rgb_to_lab(float r, float g, float b, float *ll, float *la, float *lb);
-void rgb_to_xyz(float r, float g, float b, float *x, float *y, float *z);
 unsigned int rgb_to_cpack(float r, float g, float b);
 unsigned int hsv_to_cpack(float h, float s, float v);
 
@@ -131,8 +128,6 @@ void rgba_uchar_to_float(float r_col[4], const unsigned char col_ub[4]);
 void rgb_float_to_uchar(unsigned char r_col[3], const float col_f[3]);
 void rgba_float_to_uchar(unsigned char r_col[4], const float col_f[4]);
 
-void xyz_to_lab(float x, float y, float z, float *l, float *a, float *b);
-
 MINLINE float rgb_to_grayscale(const float rgb[3]);
 MINLINE unsigned char rgb_to_grayscale_byte(const unsigned char rgb[3]);
 

source/blender/blenlib/intern/math_color.c

@@ -357,29 +357,6 @@ void hsv_clamp_v(float hsv[3], float v_max)
 	CLAMP(hsv[2], 0.0f, v_max);
 }
 
-/*http://brucelindbloom.com/index.html?Eqn_RGB_XYZ_Matrix.html */
-
-void xyz_to_rgb(float xc, float yc, float zc, float *r, float *g, float *b, int colorspace)
-{
-	switch (colorspace) {
-		case BLI_XYZ_SMPTE:
-			*r = (3.50570f * xc) + (-1.73964f * yc) + (-0.544011f * zc);
-			*g = (-1.06906f * xc) + (1.97781f * yc) + (0.0351720f * zc);
-			*b = (0.0563117f * xc) + (-0.196994f * yc) + (1.05005f * zc);
-			break;
-		case BLI_XYZ_REC709_SRGB:
-			*r = (3.240476f * xc) + (-1.537150f * yc) + (-0.498535f * zc);
-			*g = (-0.969256f * xc) + (1.875992f * yc) + (0.041556f * zc);
-			*b = (0.055648f * xc) + (-0.204043f * yc) + (1.057311f * zc);
-			break;
-		case BLI_XYZ_CIE:
-			*r = (2.28783848734076f * xc) + (-0.833367677835217f * yc) + (-0.454470795871421f * zc);
-			*g = (-0.511651380743862f * xc) + (1.42275837632178f * yc) + (0.0888930017552939f * zc);
-			*b = (0.00572040983140966f * xc) + (-0.0159068485104036f * yc) + (1.0101864083734f * zc);
-			break;
-	}
-}
-
 /**
  * We define a 'cpack' here as a (3 byte color code) number that can be expressed like 0xFFAA66 or so.
  * for that reason it is sensitive for endianness... with this function it works correctly.
@@ -618,64 +595,6 @@ void BLI_init_srgb_conversion(void)
 		BLI_color_to_srgb_table[i] = (unsigned short)(b * 0x100);
 	}
 }
-static float inverse_srgb_companding(float v)
-{
-	if (v > 0.04045f) {
-		return powf((v + 0.055f) / 1.055f, 2.4f);
-	}
-	else {
-		return v / 12.92f;
-	}
-}
-
-/**
- * \note Does sRGB to linear conversion
- */
-void rgb_to_xyz(float r, float g, float b, float *x, float *y, float *z)
-{
-	r = inverse_srgb_companding(r) * 100.0f;
-	g = inverse_srgb_companding(g) * 100.0f;
-	b = inverse_srgb_companding(b) * 100.0f;
-
-	*x = r * 0.412453f + g * 0.357580f + b * 0.180423f;
-	*y = r * 0.212671f + g * 0.715160f + b * 0.072169f;
-	*z = r * 0.019334f + g * 0.119193f + b * 0.950227f;
-}
-
-static float xyz_to_lab_component(float v)
-{
-	const float eps = 0.008856f;
-	const float k = 903.3f;
-
-	if (v > eps) {
-		return powf(v, 1.0f / 3.0f);
-	}
-	else {
-		return (k * v + 16.0f) / 116.0f;
-	}
-}
-
-void xyz_to_lab(float x, float y, float z, float *l, float *a, float *b)
-{
-	const float xr = x / 95.047f;
-	const float yr = y / 100.0f;
-	const float zr = z / 108.883f;
-
-	const float fx = xyz_to_lab_component(xr);
-	const float fy = xyz_to_lab_component(yr);
-	const float fz = xyz_to_lab_component(zr);
-
-	*l = 116.0f * fy - 16.0f;
-	*a = 500.0f * (fx - fy);
-	*b = 200.0f * (fy - fz);
-}
-
-void rgb_to_lab(float r, float g, float b, float *ll, float *la, float *lb)
-{
-	float x, y, z;
-	rgb_to_xyz(r, g, b, &x, &y, &z);
-	xyz_to_lab(x, y, z, ll, la, lb);
-}
 
 /* ****************************** blackbody ******************************** */
 

source/blender/imbuf/IMB_colormanagement.h

@@ -71,6 +71,8 @@ const char *IMB_colormanagement_get_rect_colorspace(struct ImBuf *ibuf);
 
 BLI_INLINE float IMB_colormanagement_get_luminance(const float rgb[3]);
 BLI_INLINE unsigned char IMB_colormanagement_get_luminance_byte(const unsigned char[3]);
+BLI_INLINE void IMB_colormangement_xyz_to_rgb(float rgb[3], const float xyz[3]);
+BLI_INLINE void IMB_colormangement_rgb_to_xyz(float xyz[3], const float rgb[3]);
 
 /* ** Color space transformation functions ** */
 void IMB_colormanagement_transform(float *buffer, int width, int height, int channels,
@@ -99,6 +101,9 @@ void IMB_colormanagement_colorspace_to_scene_linear(float *buffer, int width, in
 void IMB_colormanagement_scene_linear_to_color_picking_v3(float pixel[3]);
 void IMB_colormanagement_color_picking_to_scene_linear_v3(float pixel[3]);
 
+void IMB_colormanagement_scene_linear_to_srgb_v3(float pixel[3]);
+void IMB_colormanagement_srgb_to_scene_linear_v3(float pixel[3]);
+
 void IMB_colormanagement_scene_linear_to_display_v3(float pixel[3], struct ColorManagedDisplay *display);
 void IMB_colormanagement_display_to_scene_linear_v3(float pixel[3], struct ColorManagedDisplay *display);
 

source/blender/imbuf/intern/IMB_colormanagement_intern.h

@@ -42,6 +42,8 @@ struct OCIO_ConstProcessorRcPtr;
 struct ImBuf;
 
 extern float imbuf_luma_coefficients[3];
+extern float imbuf_xyz_to_rgb[3][3];
+extern float imbuf_rgb_to_xyz[3][3];
 
 #define MAX_COLORSPACE_NAME          64
 #define MAX_COLORSPACE_DESCRIPTION  512

source/blender/imbuf/intern/colormanagement.c

@@ -93,10 +93,12 @@ static int global_tot_display = 0;
 static int global_tot_view = 0;
 static int global_tot_looks = 0;
 
-/* Set to ITU-BT.709 / sRGB primaries weight. Brute force stupid, but only
+/* Luma coefficients and XYZ to RGB to be initialized by OCIO. */
- * option with no colormanagement in place.
+float imbuf_luma_coefficients[3] = {0.0f};
- */
+float imbuf_xyz_to_rgb[3][3] = {{0.0f}};
-float imbuf_luma_coefficients[3] = { 0.2126f, 0.7152f, 0.0722f };
+float imbuf_rgb_to_xyz[3][3] = {{0.0f}};
+float imbuf_xyz_to_linear_srgb[3][3] = {{0.0f}};
+float imbuf_linear_srgb_to_xyz[3][3] = {{0.0f}};
 
 /* lock used by pre-cached processors getters, so processor wouldn't
  * be created several times
@@ -563,6 +565,10 @@ static void colormanage_load_config(OCIO_ConstConfigRcPtr *config)
 
 	/* Load luminance coefficients. */
 	OCIO_configGetDefaultLumaCoefs(config, imbuf_luma_coefficients);
+	OCIO_configGetXYZtoRGB(config, imbuf_xyz_to_rgb);
+	invert_m3_m3(imbuf_rgb_to_xyz, imbuf_xyz_to_rgb);
+	copy_m3_m3(imbuf_xyz_to_linear_srgb, OCIO_XYZ_TO_LINEAR_SRGB);
+	invert_m3_m3(imbuf_linear_srgb_to_xyz, imbuf_xyz_to_linear_srgb);
 }
 
 static void colormanage_free_config(void)
@@ -1927,6 +1933,14 @@ void IMB_colormanagement_colorspace_to_scene_linear(float *buffer, int width, in
 	}
 }
 
+/* Conversion between color picking role. Typically we would expect such a
+ * requirements:
+ * - It is approximately perceptually linear, so that the HSV numbers and
+ *   the HSV cube/circle have an intuitive distribution.
+ * - It has the same gamut as the scene linear color space.
+ * - Color picking values 0..1 map to scene linear values in the 0..1 range,
+ *   so that picked albedo values are energy conserving.
+ */
 void IMB_colormanagement_scene_linear_to_color_picking_v3(float pixel[3])
 {
 	if (!global_color_picking_state.processor_to && !global_color_picking_state.failed) {
@@ -1975,6 +1989,22 @@ void IMB_colormanagement_color_picking_to_scene_linear_v3(float pixel[3])
 	}
 }
 
+/* Conversion between sRGB, for rare cases like hex color or copy/pasting
+ * between UI theme and scene linear colors. */
+void IMB_colormanagement_scene_linear_to_srgb_v3(float pixel[3])
+{
+	mul_m3_v3(imbuf_rgb_to_xyz, pixel);
+	mul_m3_v3(imbuf_xyz_to_linear_srgb, pixel);
+	linearrgb_to_srgb_v3_v3(pixel, pixel);
+}
+
+void IMB_colormanagement_srgb_to_scene_linear_v3(float pixel[3])
+{
+	srgb_to_linearrgb_v3_v3(pixel, pixel);
+	mul_m3_v3(imbuf_linear_srgb_to_xyz, pixel);
+	mul_m3_v3(imbuf_xyz_to_rgb, pixel);
+}
+
 /* convert pixel from scene linear to display space using default view
  * used by performance-critical areas such as color-related widgets where we want to reduce
  * amount of per-widget allocations

source/blender/imbuf/intern/colormanagement_inline.c

@@ -62,4 +62,14 @@ unsigned char IMB_colormanagement_get_luminance_byte(const unsigned char rgb[3])
 	return unit_float_to_uchar_clamp(val);
 }
 
+void IMB_colormangement_xyz_to_rgb(float rgb[3], const float xyz[3])
+{
+	mul_v3_m3v3(rgb, imbuf_xyz_to_rgb, xyz);
+}
+
+void IMB_colormangement_rgb_to_xyz(float xyz[3], const float rgb[3])
+{
+	mul_v3_m3v3(xyz, imbuf_rgb_to_xyz, rgb);
+}
+
 #endif  /* __IMB_COLORMANAGEMENT_INLINE_H__ */