diff options
Diffstat (limited to 'hsv2rgb.h')
| -rw-r--r-- | hsv2rgb.h | 41 |
1 files changed, 41 insertions, 0 deletions
@@ -3,6 +3,7 @@ #include "pixeltypes.h" +FASTLED_NAMESPACE_BEGIN // hsv2rgb_rainbow - convert a hue, saturation, and value to RGB // using a visually balanced rainbow (vs a straight @@ -45,4 +46,44 @@ void hsv2rgb_raw(const struct CHSV& hsv, struct CRGB & rgb); void hsv2rgb_raw(const struct CHSV* phsv, struct CRGB * prgb, int numLeds); #define HUE_MAX 191 + +// rgb2hsv_approximate - recover _approximate_ HSV values from RGB. +// +// NOTE 1: This function is a long-term work in process; expect +// results to change slightly over time as this function is +// refined and improved. +// +// NOTE 2: This function is most accurate when the input is an +// RGB color that came from a fully-saturated HSV color to start +// with. E.g. CHSV( hue, 255, 255) -> CRGB -> CHSV will give +// best results. +// +// NOTE 3: This function is not nearly as fast as HSV-to-RGB. +// It is provided for those situations when the need for this +// function cannot be avoided, or when extremely high performance +// is not needed. +// +// NOTE 4: Why is this 'only' an "approximation"? +// Not all RGB colors have HSV equivalents! For example, there +// is no HSV value that will ever convert to RGB(255,255,0) using +// the code provided in this library. So if you try to +// convert RGB(255,255,0) 'back' to HSV, you'll necessarily get +// only an approximation. Emphasis has been placed on getting +// the 'hue' as close as usefully possible, but even that's a bit +// of a challenge. The 8-bit HSV and 8-bit RGB color spaces +// are not a "bijection". +// +// Nevertheless, this function does a pretty good job, particularly +// at recovering the 'hue' from fully saturated RGB colors that +// originally came from HSV rainbow colors. So if you start +// with CHSV(hue_in,255,255), and convert that to RGB, and then +// convert it back to HSV using this function, the resulting output +// hue will either exactly the same, or very close (+/-1). +// The more desaturated the original RGB color is, the rougher the +// approximation, and the less accurate the results. +// +CHSV rgb2hsv_approximate( const CRGB& rgb); + +FASTLED_NAMESPACE_END + #endif |