91 lines
3.6 KiB
C
91 lines
3.6 KiB
C
#ifndef __INC_HSV2RGB_H
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#define __INC_HSV2RGB_H
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#include "FastLED.h"
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#include "pixeltypes.h"
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FASTLED_NAMESPACE_BEGIN
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// hsv2rgb_rainbow - convert a hue, saturation, and value to RGB
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// using a visually balanced rainbow (vs a straight
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// mathematical spectrum).
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// This 'rainbow' yields better yellow and orange
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// than a straight 'spectrum'.
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//
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// NOTE: here hue is 0-255, not just 0-191
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void hsv2rgb_rainbow( const struct CHSV& hsv, struct CRGB& rgb);
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void hsv2rgb_rainbow( const struct CHSV* phsv, struct CRGB * prgb, int numLeds);
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#define HUE_MAX_RAINBOW 255
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// hsv2rgb_spectrum - convert a hue, saturation, and value to RGB
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// using a mathematically straight spectrum (vs
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// a visually balanced rainbow).
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// This 'spectrum' will have more green & blue
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// than a 'rainbow', and less yellow and orange.
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//
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// NOTE: here hue is 0-255, not just 0-191
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void hsv2rgb_spectrum( const struct CHSV& hsv, struct CRGB& rgb);
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void hsv2rgb_spectrum( const struct CHSV* phsv, struct CRGB * prgb, int numLeds);
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#define HUE_MAX_SPECTRUM 255
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// hsv2rgb_raw - convert hue, saturation, and value to RGB.
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// This 'spectrum' conversion will be more green & blue
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// than a real 'rainbow', and the hue is specified just
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// in the range 0-191. Together, these result in a
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// slightly faster conversion speed, at the expense of
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// color balance.
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//
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// NOTE: Hue is 0-191 only!
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// Saturation & value are 0-255 each.
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//
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void hsv2rgb_raw(const struct CHSV& hsv, struct CRGB & rgb);
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void hsv2rgb_raw(const struct CHSV* phsv, struct CRGB * prgb, int numLeds);
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#define HUE_MAX 191
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// rgb2hsv_approximate - recover _approximate_ HSV values from RGB.
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//
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// NOTE 1: This function is a long-term work in process; expect
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// results to change slightly over time as this function is
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// refined and improved.
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//
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// NOTE 2: This function is most accurate when the input is an
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// RGB color that came from a fully-saturated HSV color to start
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// with. E.g. CHSV( hue, 255, 255) -> CRGB -> CHSV will give
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// best results.
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//
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// NOTE 3: This function is not nearly as fast as HSV-to-RGB.
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// It is provided for those situations when the need for this
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// function cannot be avoided, or when extremely high performance
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// is not needed.
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//
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// NOTE 4: Why is this 'only' an "approximation"?
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// Not all RGB colors have HSV equivalents! For example, there
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// is no HSV value that will ever convert to RGB(255,255,0) using
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// the code provided in this library. So if you try to
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// convert RGB(255,255,0) 'back' to HSV, you'll necessarily get
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// only an approximation. Emphasis has been placed on getting
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// the 'hue' as close as usefully possible, but even that's a bit
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// of a challenge. The 8-bit HSV and 8-bit RGB color spaces
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// are not a "bijection".
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//
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// Nevertheless, this function does a pretty good job, particularly
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// at recovering the 'hue' from fully saturated RGB colors that
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// originally came from HSV rainbow colors. So if you start
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// with CHSV(hue_in,255,255), and convert that to RGB, and then
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// convert it back to HSV using this function, the resulting output
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// hue will either exactly the same, or very close (+/-1).
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// The more desaturated the original RGB color is, the rougher the
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// approximation, and the less accurate the results.
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//
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CHSV rgb2hsv_approximate( const CRGB& rgb);
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FASTLED_NAMESPACE_END
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#endif
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