imported from "final" folder

.pio/libdeps/esp01_1m/FastLED/apa102fix.md

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+I was dissatisfied with a gamma corrected ramp using the APA102HD mode (it seemed to visibly step at one or more points), and some analysis of the 8 bit rgb + 5 bit brightness function showed why:
+https://www.argyllcms.com/APA102_loglog.svg.
+
+So here is a suggested replacement for five_bit_bitshift() in fl/five_bit_hd_gamma.cpp, that fixed the problem for me:
+
+// Improved FastLED five_bit_bitshift() function
+// This appears to exactly match the floating point reference,
+// with a worst case resulting error of 0.2% over the full 16 bit input range,
+// and an average error of 0.05% over that range. Errors scale with maximum
+// magnitude.
+
+// ix/31 * 255/65536 * 256 scaling factors, valid for indexes 1..31
+static uint32_t bright_scale[32] =  {
+    0, 2023680, 1011840, 674560, 505920, 404736, 337280, 289097,
+    252960, 224853, 202368, 183971, 168640, 155668, 144549, 134912,
+    126480, 119040, 112427, 106509, 101184, 96366, 91985, 87986,
+    84320, 80947, 77834, 74951, 72274, 69782, 67456, 65280
+};
+
+// Since the return value wasn't used, it has been omitted.
+// It's not clear what scale brightness is, or how it is to be applied,
+// so we assume 8 bits applied over the given rgb values.
+void five_bit_bitshift(uint16_t r16, uint16_t g16, uint16_t b16, uint8_t brightness,
+                          CRGB *out, uint8_t *out_power_5bit) {
+    uint8_t r8 = 0, g8 = 0, b8 = 0;
+
+    // Apply any brightness setting (we assume brightness is 0..255)
+    if (brightness != 0xff) {
+        r16 = scale16by8(r16, brightness);
+        g16 = scale16by8(g16, brightness);
+        b16 = scale16by8(b16, brightness);
+    }
+
+    // Locate the largest value to set the brightness/scale factor
+    uint16_t scale = max3(r16, g16, b16);
+
+    if (scale == 0) {
+        *out = CRGB(0, 0, 0);
+        *out_power_5bit = 0;
+        return;
+    } else {
+        uint32_t scalef;
+
+        // Compute 5 bit quantized scale that is at or above the maximum value.
+        scale = (scale + (2047 - (scale >> 5))) >> 11;
+
+        // Adjust the 16 bit values to account for the scale, then round to 8 bits
+        scalef = bright_scale[scale];
+        r8 = (r16 * scalef + 0x808000) >> 24;
+        g8 = (g16 * scalef + 0x808000) >> 24;
+        b8 = (b16 * scalef + 0x808000) >> 24;
+
+        *out = CRGB(r8, g8, b8);
+        *out_power_5bit = scale;
+        return;
+    }
+}