add utility function to BLI_math_color - rgb_to_luma, rgb_to_luma_byte, also use rgb_to_grayscale in more places.

2 files changed, 16 insertions, 4 deletions

diff --git a/source/blender/blenlib/BLI_math_color.h b/source/blender/blenlib/BLI_math_color.h
index 2d8b0188165..6d37aabd6ab 100644
--- a/source/blender/blenlib/BLI_math_color.h
+++ b/source/blender/blenlib/BLI_math_color.h
@@ -69,8 +69,10 @@ void rgb_to_hsv_compat(float r, float g, float b, float *lh, float *ls, float *l
 unsigned int rgb_to_cpack(float r, float g, float b);
 unsigned int hsv_to_cpack(float h, float s, float v);
 
-float rgb_to_grayscale(float rgb[3]);
-unsigned char rgb_to_grayscale_byte(unsigned char rgb[3]);
+float rgb_to_grayscale(const float rgb[3]);
+unsigned char rgb_to_grayscale_byte(const unsigned char rgb[3]);
+float rgb_to_luma(const float rgb[3]);
+unsigned char rgb_to_luma_byte(const unsigned char rgb[3]);
 
 /**************** Profile Transformations *****************/
 
diff --git a/source/blender/blenlib/intern/math_color.c b/source/blender/blenlib/intern/math_color.c
index e9e700d355a..20df893015d 100644
--- a/source/blender/blenlib/intern/math_color.c
+++ b/source/blender/blenlib/intern/math_color.c
@@ -434,16 +434,26 @@ int constrain_rgb(float *r, float *g, float *b)
 	return 0;                         /* Color within RGB gamut */
 }
 
-float rgb_to_grayscale(float rgb[3])
+float rgb_to_grayscale(const float rgb[3])
 {
 	return 0.3f*rgb[0] + 0.58f*rgb[1] + 0.12f*rgb[2];
 }
 
-unsigned char rgb_to_grayscale_byte(unsigned char rgb[3])
+unsigned char rgb_to_grayscale_byte(const unsigned char rgb[3])
 {
 	return (76*(unsigned short)rgb[0] + 148*(unsigned short)rgb[1] + 31*(unsigned short)rgb[2]) / 255;
 }
 
+float rgb_to_luma(const float rgb[3])
+{
+	return 0.299f*rgb[0] + 0.587f*rgb[1] + 0.114f*rgb[2];
+}
+
+unsigned char rgb_to_luma_byte(const unsigned char rgb[3])
+{
+	return (76*(unsigned short)rgb[0] + 150*(unsigned short)rgb[1] + 29*(unsigned short)rgb[2]) / 255;
+}
+
 /* ********************************* lift/gamma/gain / ASC-CDL conversion ********************************* */
 
 void lift_gamma_gain_to_asc_cdl(float *lift, float *gamma, float *gain, float *offset, float *slope, float *power)