Add fill_rainbow_endless util functions

For filling a rainbow pattern that's continuous in hue between the end of the strip and the beginning. Useful for out-of-the-box rainbow animations on looped strips and LED rings.

3 files changed, 55 insertions, 0 deletions

diff --git a/keywords.txt b/keywords.txt
index 75df500c..91e7b3b1 100644
--- a/keywords.txt
+++ b/keywords.txt
@@ -131,6 +131,7 @@ fill_gradient	KEYWORD2
 fill_gradient_RGB	KEYWORD2
 fill_palette	KEYWORD2
 fill_rainbow	KEYWORD2
+fill_rainbow_endless	KEYWORD2
 fill_solid	KEYWORD2
 map_data_into_colors_through_palette	KEYWORD2
 nblend	KEYWORD2
diff --git a/src/colorutils.cpp b/src/colorutils.cpp
index a1acaa5a..d1f45bd9 100644
--- a/src/colorutils.cpp
+++ b/src/colorutils.cpp
@@ -62,6 +62,45 @@ void fill_rainbow( struct CHSV * targetArray, int numToFill,
 }
 
 
+void fill_rainbow_endless(struct CRGB* targetArray, int numToFill, uint8_t initialhue)
+{
+    if (numToFill == 0) return;  // avoiding div/0
+
+    CHSV hsv;
+    hsv.hue = initialhue;
+    hsv.val = 255;
+    hsv.sat = 240;
+
+    const uint16_t hueChange = 65536 / (uint16_t)numToFill;  // hue change for each LED, * 256 for precision
+    uint16_t hueOffset = 0;  // offset for hue value, with precision (*256)
+
+    for (int i = 0; i < numToFill; ++i) {
+        targetArray[i] = hsv;
+        hueOffset += hueChange;  // increase precise offset
+        hsv.hue = initialhue + (uint8_t)(hueOffset >> 8);  // assign new hue with precise offset (as 8-bit)
+    }
+}
+
+void fill_rainbow_endless(struct CHSV* targetArray, int numToFill, uint8_t initialhue)
+{
+    if (numToFill == 0) return;  // avoiding div/0
+
+    CHSV hsv;
+    hsv.hue = initialhue;
+    hsv.val = 255;
+    hsv.sat = 240;
+
+    const uint16_t hueChange = 65536 / (uint16_t)numToFill;  // hue change for each LED, * 256 for precision
+    uint16_t hueOffset = 0;  // offset for hue value, with precision (*256)
+
+    for (int i = 0; i < numToFill; ++i) {
+        targetArray[i] = hsv;
+        hueOffset += hueChange;  // increase precise offset
+        hsv.hue = initialhue + (uint8_t)(hueOffset >> 8);  // assign new hue with precise offset (as 8-bit)
+    }
+}
+
+
 void fill_gradient_RGB( CRGB* leds,
                    uint16_t startpos, CRGB startcolor,
                    uint16_t endpos,   CRGB endcolor )
diff --git a/src/colorutils.h b/src/colorutils.h
index f09d525f..237e9400 100644
--- a/src/colorutils.h
+++ b/src/colorutils.h
@@ -37,6 +37,21 @@ void fill_rainbow( struct CHSV * targetArray, int numToFill,
                    uint8_t deltahue = 5);
 
 
+/// fill_rainbow_endless - fill a range of LEDs with a rainbow of colors, at
+///                        full saturation and full value (brightness),
+///                        so that the hues are continuous between the end
+///                        of the strip and the beginning
+void fill_rainbow_endless(struct CRGB* targetArray, int numToFill,
+                          uint8_t initialhue);
+
+/// fill_rainbow_endless - fill a range of LEDs with a rainbow of colors, at
+///                        full saturation and full value (brightness),
+///                        so that the hues are continuous between the end
+///                        of the strip and the beginning
+void fill_rainbow_endless(struct CHSV* targetArray, int numToFill,
+                          uint8_t initialhue);
+
+
 // fill_gradient - fill an array of colors with a smooth HSV gradient
 //                 between two specified HSV colors.
 //                 Since 'hue' is a value around a color wheel,