* Color conversion between RGB and HSV color spaces. HSV stands for Hue-Saturation-Value. "Hue" has a range of [0,2*PI] * and "Saturation" has a range of [0,1], the two together represent the color. While "Value" has the same range as the - * input pixels and represents how light/dark the color is. + * input pixels and represents how light/dark the color is. Original algorithm taken from [1] and modified slightly. *
* ** NOTE: The hue is represented in radians instead of degrees, as is often done. + * NOTE: Hue will be set to NaN if it is undefined. It is undefined when chroma is zero, which happens when the input + * color is a pure gray (e.g. same value across all color bands). + *
+ * + *
+ * RGB to HSV:
+ *
+ * min = min(r,g,b) + * max = max(r,g,b) + * delta = max-min // this is the chroma + * value = max + * + * if( max != 0 ) + * saturation = delta/max + * else + * saturation = 0; + * hue = NaN + * + * if( r == max ) + * hue = (g-b)/delta + * else if( g == max ) + * hue = 2 + (b-r)/delta + * else + * hue = 4 + (r-g)/delta + * + * hue *= 60.0*PI/180.0 + * if( hue < 0 ) + * hue += 2.0*PI + * + *+ * + * + *
+ * [1] http://www.cs.rit.edu/~ncs/color/t_convert.html *
* * @author Peter Abeles @@ -53,7 +87,6 @@ This doesn't seem to improve the runtime noticeably and makes the code uglier. */ - public class ColorHsv { // 60 degrees in radians diff --git a/main/ip/test/boofcv/alg/color/TestColorHsv.java b/main/ip/test/boofcv/alg/color/TestColorHsv.java index 35eb85e765..037d3f2ac5 100644 --- a/main/ip/test/boofcv/alg/color/TestColorHsv.java +++ b/main/ip/test/boofcv/alg/color/TestColorHsv.java @@ -52,6 +52,10 @@ public void backAndForth_F64_and_F32() { check(0.25, 0.5, 0.75); check(0.8, 0.1, 0.75); check(151, 151, 151); + check(151, 120, 120); + check(120, 151, 120); + check(120, 120, 151); + for( int i = 0; i < 50; i++ ) { double r = rand.nextDouble();