Bug in Neopixel getPixelColor function - and proposed fix for library

[KayleeAmelia]

Hi all,
I... have never done a github upload before. So I hope I'm doing this right.

I noticed a problem with the getPixelColor function in Neopixel library, when using non-default brightness settings. Comments on lines 3311-3315 note innaccuracy as a known issue, however, I have managed to fix it.

In "Adafruit_NeoPixel.cpp", from line 3310 onwards:

if (brightness) {
      // Stored color was decimated by setBrightness(). Returned value
      // attempts to scale back to an approximation of the original 24-bit
      // value used when setting the pixel color, but there will always be
      // some error -- those bits are simply gone. Issue is most
      // pronounced at low brightness levels.
      
	  return (((uint32_t)(p[rOffset] *255) / (brightness-1)) << 16) |
             (((uint32_t)(p[gOffset] *255) / (brightness-1)) << 8) |
             ((uint32_t)(p[bOffset] *255) / (brightness-1));//returns the adjusted rgb colour, accounting for brightness.
	//old return was return (((uint32_t)(p[rOffset] << 8) / brightness) << 16) |
        //     (((uint32_t)(p[gOffset] << 8) / brightness) << 8) |
        //     ((uint32_t)(p[bOffset] << 8) / brightness);
    }

And a bit further along:

    } else { // Is RGBW-type device
    p = &pixels[n * 4];
    if (brightness) { // Return scaled color
      return (((uint32_t)(p[wOffset] *255) / (brightness-1)) << 24) |
             (((uint32_t)(p[rOffset] *255) / (brightness-1)) << 16) |
             (((uint32_t)(p[gOffset] *255) / (brightness-1)) << 8) |
             ((uint32_t)(p[bOffset] *255) / (brightness-1));
	  /*return (((uint32_t)(p[wOffset] << 8) / brightness) << 24) |
             (((uint32_t)(p[rOffset] << 8) / brightness) << 16) |
             (((uint32_t)(p[gOffset] << 8) / brightness) << 8) |
             ((uint32_t)(p[bOffset] << 8) / brightness);
	  */ //old version
    } else { // Return raw color

In short, it seems that the error was an 'off by one' type error.
I have thoroughly tested the first block using an ESP32-S3, but cannot test the second block, as I do not have RGBW LEDs.
Tested using ESP32-S3 on Arduino IDE 2.3.0

How have I tested this? My sketch repeatedly grabs the old colour from a neopixel, changed it, then changes it back. I have left this running for several hours, and the only rounding error is the initial rounding used from the first setPixelColor command with brightness applied, and restoring and re-writing the colour several thousand times has produced no further rounding errors.
I offer this fix, in the hope that it helps someone, and hoping the fix makes it into the next update for Neopixel library.