small optimization for color_blend

* Early exit when color1 == color2 (nothing to blend)
* pre-calculate `blendmax - blend` (repeated 4 times)

Author: softhack007

wled00/colors.cpp

@@ -9,9 +9,11 @@
  */
 IRAM_ATTR_YN uint32_t color_blend(uint32_t color1, uint32_t color2, uint_fast16_t blend, bool b16) {
   if(blend == 0)   return color1;
-  uint_fast16_t blendmax = b16 ? 0xFFFF : 0xFF;
+  if (color1 == color2) return color1;  // WLEDMM shortcut
+  const uint_fast16_t blendmax = b16 ? 0xFFFF : 0xFF;
   if(blend == blendmax) return color2;
   const uint_fast8_t shift = b16 ? 16 : 8;
+  const uint_fast16_t blend2 = blendmax - blend; // WLEDMM pre-calculate value
 
   uint32_t w1 = W(color1);
   uint32_t r1 = R(color1);
@@ -23,10 +25,10 @@ IRAM_ATTR_YN uint32_t color_blend(uint32_t color1, uint32_t color2, uint_fast16_
   uint32_t g2 = G(color2);
   uint32_t b2 = B(color2);
 
-  uint32_t w3 = ((w2 * blend) + (w1 * (blendmax - blend))) >> shift;
-  uint32_t r3 = ((r2 * blend) + (r1 * (blendmax - blend))) >> shift;
-  uint32_t g3 = ((g2 * blend) + (g1 * (blendmax - blend))) >> shift;
-  uint32_t b3 = ((b2 * blend) + (b1 * (blendmax - blend))) >> shift;
+  uint32_t w3 = ((w2 * blend) + (w1 * blend2)) >> shift;
+  uint32_t r3 = ((r2 * blend) + (r1 * blend2)) >> shift;
+  uint32_t g3 = ((g2 * blend) + (g1 * blend2)) >> shift;
+  uint32_t b3 = ((b2 * blend) + (b1 * blend2)) >> shift;
 
   return RGBW32(r3, g3, b3, w3);
 }