Adding center bin selection to 2D GEQ (#4764)

* adding center bin selection to 2D GEQ: this makes it possible to use subsets of the GEQ on distributed strips

setting custom3 to 0 gives the "old" behaviour, this is the default. existing presets will have the custom3 slider at the center, changing presets that do not use the full width so this is a breaking change for those but I assume theser are rare.

Author: DedeHai

wled00/FX.cpp

@@ -7275,6 +7275,7 @@ uint16_t mode_2DGEQ(void) { // By Will Tatam. Code reduction by Ewoud Wijma.
   if (!strip.isMatrix || !SEGMENT.is2D()) return mode_static(); // not a 2D set-up
 
   const int NUM_BANDS = map(SEGMENT.custom1, 0, 255, 1, 16);
+  const int CENTER_BIN = map(SEGMENT.custom3, 0, 31, 0, 15);
   const int cols = SEG_W;
   const int rows = SEG_H;
 
@@ -7296,8 +7297,14 @@ uint16_t mode_2DGEQ(void) { // By Will Tatam. Code reduction by Ewoud Wijma.
   if ((fadeoutDelay <= 1 ) || ((SEGENV.call % fadeoutDelay) == 0)) SEGMENT.fadeToBlackBy(SEGMENT.speed);
 
   for (int x=0; x < cols; x++) {
-    uint8_t  band       = map(x, 0, cols, 0, NUM_BANDS);
-    if (NUM_BANDS < 16) band = map(band, 0, NUM_BANDS - 1, 0, 15); // always use full range. comment out this line to get the previous behaviour.
+    int band = map(x, 0, cols, 0, NUM_BANDS);
+    if (NUM_BANDS < 16) {
+        int startBin = constrain(CENTER_BIN - NUM_BANDS/2, 0, 15 - NUM_BANDS + 1);
+        if(NUM_BANDS <= 1)
+          band = CENTER_BIN; // map() does not work for single band
+        else
+          band = map(band, 0, NUM_BANDS - 1, startBin, startBin + NUM_BANDS - 1);
+    }
     band = constrain(band, 0, 15);
     unsigned colorIndex = band * 17;
     int barHeight  = map(fftResult[band], 0, 255, 0, rows); // do not subtract -1 from rows here
@@ -7319,7 +7326,7 @@ uint16_t mode_2DGEQ(void) { // By Will Tatam. Code reduction by Ewoud Wijma.
 
   return FRAMETIME;
 } // mode_2DGEQ()
-static const char _data_FX_MODE_2DGEQ[] PROGMEM = "GEQ@Fade speed,Ripple decay,# of bands,,,Color bars;!,,Peaks;!;2f;c1=255,c2=64,pal=11,si=0"; // Beatsin
+static const char _data_FX_MODE_2DGEQ[] PROGMEM = "GEQ@Fade speed,Ripple decay,# of bands,,Bin,Color bars;!,,Peaks;!;2f;c1=255,c2=64,pal=11,si=0,c3=0";
 
 
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