From 8b4c6f303af08fd52fd0debd936a36ed522abc43 Mon Sep 17 00:00:00 2001
From: Greger <gregersn@gmail.com>
Date: Mon, 2 Nov 2015 19:15:01 +0100
Subject: [PATCH] added function to set only one color channel without touching
 the others

---
 Adafruit_NeoPixel.cpp | 30 ++++++++++++++++++++++++++++++
 Adafruit_NeoPixel.h   |  1 +
 2 files changed, 31 insertions(+)

diff --git a/Adafruit_NeoPixel.cpp b/Adafruit_NeoPixel.cpp
index 916e721d..7cf7ab71 100644
--- a/Adafruit_NeoPixel.cpp
+++ b/Adafruit_NeoPixel.cpp
@@ -1195,6 +1195,36 @@ void Adafruit_NeoPixel::setPixelColor(uint16_t n, uint32_t c) {
   }
 }
 
+// Set the r, g or b value of a single pixel
+void Adafruit_NeoPixel::setPixelChannel(uint16_t n, uint8_t v, uint8_t c) {
+  // set channel (red, green or blue) 'c' of pixel n to value v
+  if(n < numLEDs) {
+    uint8_t *p;
+    uint8_t offset;
+    if(c == 0) {
+      offset = rOffset;
+    } else if(c == 1) {
+      offset = gOffset;
+    } else if(c == 2) {
+      offset = bOffset;
+    } else {
+      return;
+    }
+
+    if(wOffset == rOffset) {
+      p = &pixels[n * 3];
+    } else {
+      p = &pixels[n * 4];
+    }
+    if(brightness) {
+       v = (v * brightness) >> 8; 
+    }
+
+    p[offset] = v;
+    
+  }
+}
+
 // Convert separate R,G,B into packed 32-bit RGB color.
 // Packed format is always RGB, regardless of LED strand color order.
 uint32_t Adafruit_NeoPixel::Color(uint8_t r, uint8_t g, uint8_t b) {
diff --git a/Adafruit_NeoPixel.h b/Adafruit_NeoPixel.h
index c32e3bf0..b9edd1fd 100644
--- a/Adafruit_NeoPixel.h
+++ b/Adafruit_NeoPixel.h
@@ -129,6 +129,7 @@ class Adafruit_NeoPixel {
     setPixelColor(uint16_t n, uint8_t r, uint8_t g, uint8_t b),
     setPixelColor(uint16_t n, uint8_t r, uint8_t g, uint8_t b, uint8_t w),
     setPixelColor(uint16_t n, uint32_t c),
+    setPixelChannel(uint16_t n, uint8_t v, uint8_t c),
     setBrightness(uint8_t),
     clear(),
     updateLength(uint16_t n),