using segment buffer instead of local buffer for PS (#4776)

- using segment buffer instead of local buffer to save FX ram
- fix rendering if gamma correction is disabled
- some code cleanup
- Fix for low RAM: reduce number of particles dynamically
- updated add and scale color functions to not use references
- FPS is now more consistent and on average about 15% faster

wled00/FX_fcn.cpp

@@ -645,6 +645,14 @@ uint16_t Segment::virtualLength() const {
   return vLength;
 }
 
+#ifndef WLED_DISABLE_2D
+// maximum length of a mapped 1D segment, used in PS for buffer allocation
+uint16_t Segment::maxMappingLength() const {
+  uint32_t vW = virtualWidth();
+  uint32_t vH = virtualHeight();
+  return max(sqrt32_bw(vH*vH + vW*vW), (uint32_t)getPinwheelLength(vW, vH)); // use diagonal
+}
+#endif
 // pixel is clipped if it falls outside clipping range
 // if clipping start > stop the clipping range is inverted
 bool IRAM_ATTR_YN Segment::isPixelClipped(int i) const {