【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812硬屏

实验使用的硬件，软件平台使用Arduino IDE（见《【花雕体验】15 尝试搭建Beetle ESP32 C3之Arduino开发环境》）

WS2812B
是一个集控制电路与发光电路于一体的智能外控LED光源。其外型与一个5050LED灯珠相同，每个元件即为一个像素点。像素点内部包含了智能数字接口数据锁存信号整形放大驱动电路，还包含有高精度的内部振荡器和12V高压可编程定电流控制部分，有效保证了像素点光的颜色高度一致。数据协议采用单线归零码的通讯方式，像素点在上电复位以后，DIN端接受从控制器传输过来的数据，首先送过来的24bit数据被第一个像素点提取后，送到像素点内部的数据锁存器，剩余的数据经过内部整形处理电路整形放大后通过DO端口开始转发输出给下一个级联的像素点，每经过一个像素点的传输，信号减少24bit。像素点采用自动整形转发技术，使得该像素点的级联个数不受信号传送的限制，仅仅受限信号传输速度要求。

主要特点
●     智能反接保护，电源反接不会损坏IC。
●     IC控制电路与LED点光源公用一个电源。
●     控制电路与RGB芯片集成在一个5050封装的元器件中，构成一个完整的外控像素点。
●     内置信号整形电路，任何一个像素点收到信号后经过波形整形再输出，保证线路波形畸变不会累加。
●     内置上电复位和掉电复位电路。
●     每个像素点的三基色颜色可实现256级亮度显示，完成16777216种颜色的全真色彩显示，扫描频率不低于400Hz/s。
●     串行级联接口，能通过一根信号线完成数据的接收与解码。
●     任意两点传传输距离在不超过5米时无需增加任何电路。
●     当刷新速率30帧/秒时，级联数不小于1024点。
●      数据发送速度可达800Kbps。
●      光的颜色高度一致，性价比高。

WS2812B典型应用电路

Beetle ESP32-C3是一款基于ESP32-C3 RISC-V 32位单核处理器芯片的主控板，专为物联网 (IoT) 设备而设计。Beetle ESP32-C3在仅硬币大小的体积上引出了多达13个IO口，制作项目时不必再担心IO口不够用的情况，同时主控板还集成锂电池充电管理功能，可以直接连接锂电池，不需要外围模块，同时保证应用体积和安全性。Beetle ESP32-C3配套的扩展板在未增加太大体积的情况下，引出了更多的电源，在制作项目时焊接更加方便，板载的GDI显示屏接口解决使用屏幕时的接线烦恼。实验使用的引脚为A0和D6。

8X32灯板采用独立电源供电，这里使用华为5V2A手机电源

打开Arduino IDE——工具——管理库，搜索Adafruit NeoPixel，并安装驱动库

  【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812灯板
    实验程序一：逐一点亮256个绿色LED灯

/*
  【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812灯板
  实验程序一：逐一点亮256个绿色LED灯
*/

#include <Adafruit_NeoPixel.h>

#define PIN            6
#define NUMPIXELS      256

Adafruit_NeoPixel pixels = Adafruit_NeoPixel(NUMPIXELS, PIN, NEO_GRB + NEO_KHZ800);
int delayval = 60;

void setup() {
  pixels.begin();
}

void loop() {
  for (int i = 0; i < NUMPIXELS; i++) {
    pixels.setPixelColor(i, pixels.Color(0, 30, 0));
    pixels.show();
    delay(delayval);
  }
}
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实验场景图

动态图

【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812灯板
    实验程序二：简单的流水变幻彩虹灯

/*
  【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812灯板
  实验程序二：简单的流水变幻彩虹灯
*/

#include <Adafruit_NeoPixel.h>

#define PIN 6
#define BRIGHTNESS 128

Adafruit_NeoPixel strip = Adafruit_NeoPixel(BRIGHTNESS, PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  strip.setBrightness(BRIGHTNESS);
  strip.begin();
  strip.show();
}

void loop() {
  colorWipe(strip.Color(40, 0, 0), 20); // Red
  colorWipe(strip.Color(0, 40, 0), 20); // Green
  colorWipe(strip.Color(0, 0, 50), 20); // Blue
  colorWipe(strip.Color(40, 40, 50), 20); // BlueWite
  rainbowCycle(1);

}

void colorWipe(uint32_t c, uint8_t wait) {
  for (uint16_t i = 0; i < strip.numPixels(); i++) {
    strip.setPixelColor(i, c);
    strip.show();
    delay(wait);
  }
}

void rainbow(uint8_t wait) {
  uint16_t i, j;
  for (j = 0; j < 256; j++) {
    for (i = 0; i < strip.numPixels(); i++) {
      strip.setPixelColor(i, Wheel((i + j) & 255 ));
    }
    strip.show();
    delay(wait);
  }
}

void rainbowCycle(uint8_t wait) {
  uint16_t i, j;
  for (j = 0; j < 256 * 5; j++) { // 5 cycles of all colors on wheel
    for (i = 0; i < strip.numPixels(); i++) {
      strip.setPixelColor(i, Wheel(((i * 256 / strip.numPixels()) + j) & 255));
    }
    strip.show();
    delay(wait);
  }
}

uint32_t Wheel(byte WheelPos) {
  if (WheelPos < 85) {
    return strip.Color(WheelPos * 3, 255 - WheelPos * 3, 0);
  } else if (WheelPos < 170) {
    WheelPos -= 85;
    return strip.Color(255 - WheelPos * 3, 0, WheelPos * 3);
  } else {
    WheelPos -= 170;
    return strip.Color(0, WheelPos * 3, 255 - WheelPos * 3);
  }
}
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动态图

动态图

http://bbs.eeworld.com.cn/data/a ... feq52s556iigmpj.gif

实验场景图

实验的视频记录（1分18秒）

https://v.youku.com/v_show/id_XNTg4NTQ2MDYyMA==.html?firsttime=0

  【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812灯板
  实验程序三：256位多彩流水灯变幻彩虹灯

/*
  【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812灯板
  实验程序三：256位多彩流水灯变幻彩虹灯
*/

#include <Adafruit_NeoPixel.h>

#define LED_PIN 6
#define LED_COUNT 256

Adafruit_NeoPixel strip = Adafruit_NeoPixel(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);

void setup() {
  strip.setBrightness(30);
  strip.begin();
  strip.show();
}

void loop() {
  // Fill along the length of the strip in various colors...
  colorWipe(strip.Color(255,   0,   0), 50); // Red
  colorWipe(strip.Color(  0, 255,   0), 50); // Green
  colorWipe(strip.Color(  0,   0, 255), 50); // Blue

  // Do a theater marquee effect in various colors...
  theaterChase(strip.Color(127, 127, 127), 50); // White, half brightness
  theaterChase(strip.Color(127,   0,   0), 50); // Red, half brightness
  theaterChase(strip.Color(  0,   0, 127), 50); // Blue, half brightness

  rainbow(10);             // Flowing rainbow cycle along the whole strip
  theaterChaseRainbow(50); // Rainbow-enhanced theaterChase variant
}


// Some functions of our own for creating animated effects -----------------

// Fill strip pixels one after another with a color. Strip is NOT cleared
// first; anything there will be covered pixel by pixel. Pass in color
// (as a single 'packed' 32-bit value, which you can get by calling
// strip.Color(red, green, blue) as shown in the loop() function above),
// and a delay time (in milliseconds) between pixels.
void colorWipe(uint32_t color, int wait) {
  for (int i = 0; i < strip.numPixels(); i++) { // For each pixel in strip...
    strip.setPixelColor(i, color);         //  Set pixel's color (in RAM)
    strip.show();                          //  Update strip to match
    delay(wait);                           //  Pause for a moment
  }
}

// Theater-marquee-style chasing lights. Pass in a color (32-bit value,
// a la strip.Color(r,g,b) as mentioned above), and a delay time (in ms)
// between frames.
void theaterChase(uint32_t color, int wait) {
  for (int a = 0; a < 10; a++) { // Repeat 10 times...
    for (int b = 0; b < 3; b++) { //  'b' counts from 0 to 2...
      strip.clear();         //   Set all pixels in RAM to 0 (off)
      // 'c' counts up from 'b' to end of strip in steps of 3...
      for (int c = b; c < strip.numPixels(); c += 3) {
        strip.setPixelColor(c, color); // Set pixel 'c' to value 'color'
      }
      strip.show(); // Update strip with new contents
      delay(wait);  // Pause for a moment
    }
  }
}

// Rainbow cycle along whole strip. Pass delay time (in ms) between frames.
void rainbow(int wait) {
  // Hue of first pixel runs 5 complete loops through the color wheel.
  // Color wheel has a range of 65536 but it's OK if we roll over, so
  // just count from 0 to 5*65536. Adding 256 to firstPixelHue each time
  // means we'll make 5*65536/256 = 1280 passes through this outer loop:
  for (long firstPixelHue = 0; firstPixelHue < 5 * 65536; firstPixelHue += 256) {
    for (int i = 0; i < strip.numPixels(); i++) { // For each pixel in strip...
      // Offset pixel hue by an amount to make one full revolution of the
      // color wheel (range of 65536) along the length of the strip
      // (strip.numPixels() steps):
      int pixelHue = firstPixelHue + (i * 65536L / strip.numPixels());
      // strip.ColorHSV() can take 1 or 3 arguments: a hue (0 to 65535) or
      // optionally add saturation and value (brightness) (each 0 to 255).
      // Here we're using just the single-argument hue variant. The result
      // is passed through strip.gamma32() to provide 'truer' colors
      // before assigning to each pixel:
      strip.setPixelColor(i, strip.gamma32(strip.ColorHSV(pixelHue)));
    }
    strip.show(); // Update strip with new contents
    delay(wait);  // Pause for a moment
  }
}

// Rainbow-enhanced theater marquee. Pass delay time (in ms) between frames.
void theaterChaseRainbow(int wait) {
  int firstPixelHue = 0;     // First pixel starts at red (hue 0)
  for (int a = 0; a < 30; a++) { // Repeat 30 times...
    for (int b = 0; b < 3; b++) { //  'b' counts from 0 to 2...
      strip.clear();         //   Set all pixels in RAM to 0 (off)
      // 'c' counts up from 'b' to end of strip in increments of 3...
      for (int c = b; c < strip.numPixels(); c += 3) {
        // hue of pixel 'c' is offset by an amount to make one full
        // revolution of the color wheel (range 65536) along the length
        // of the strip (strip.numPixels() steps):
        int      hue   = firstPixelHue + c * 65536L / strip.numPixels();
        uint32_t color = strip.gamma32(strip.ColorHSV(hue)); // hue -> RGB
        strip.setPixelColor(c, color); // Set pixel 'c' to value 'color'
      }
      strip.show();                // Update strip with new contents
      delay(wait);                 // Pause for a moment
      firstPixelHue += 65536 / 90; // One cycle of color wheel over 90 frames
    }
  }
}
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实验动态图

  【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812灯板
  实验程序四：256位多彩火焰灯

/*
  【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812灯板
  实验程序四：256位多彩火焰灯
*/

#include <FastLED.h>

#define LED_PIN     6
#define COLOR_ORDER GRB
#define CHIPSET     WS2811
#define NUM_LEDS    256

#define BRIGHTNESS  22
#define FRAMES_PER_SECOND 60

bool gReverseDirection = false;

CRGB leds[NUM_LEDS];

// Fire2012 with programmable Color Palette
//
// This code is the same fire simulation as the original "Fire2012",
// but each heat cell's temperature is translated to color through a FastLED
// programmable color palette, instead of through the "HeatColor(...)" function.
//
// Four different static color palettes are provided here, plus one dynamic one.
//
// The three static ones are:
//   1. the FastLED built-in HeatColors_p -- this is the default, and it looks
//      pretty much exactly like the original Fire2012.
//
//  To use any of the other palettes below, just "uncomment" the corresponding code.
//
//   2. a gradient from black to red to yellow to white, which is
//      visually similar to the HeatColors_p, and helps to illustrate
//      what the 'heat colors' palette is actually doing,
//   3. a similar gradient, but in blue colors rather than red ones,
//      i.e. from black to blue to aqua to white, which results in
//      an "icy blue" fire effect,
//   4. a simplified three-step gradient, from black to red to white, just to show
//      that these gradients need not have four components; two or
//      three are possible, too, even if they don't look quite as nice for fire.
//
// The dynamic palette shows how you can change the basic 'hue' of the
// color palette every time through the loop, producing "rainbow fire".

CRGBPalette16 gPal;

void setup() {
  delay(3000); // sanity delay
  FastLED.addLeds<CHIPSET, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection( TypicalLEDStrip );
  FastLED.setBrightness( BRIGHTNESS );

  // This first palette is the basic 'black body radiation' colors,
  // which run from black to red to bright yellow to white.
  gPal = HeatColors_p;
  
  // These are other ways to set up the color palette for the 'fire'.
  // First, a gradient from black to red to yellow to white -- similar to HeatColors_p
  //   gPal = CRGBPalette16( CRGB::Black, CRGB::Red, CRGB::Yellow, CRGB::White);
  
  // Second, this palette is like the heat colors, but blue/aqua instead of red/yellow
  //   gPal = CRGBPalette16( CRGB::Black, CRGB::Blue, CRGB::Aqua,  CRGB::White);
  
  // Third, here's a simpler, three-step gradient, from black to red to white
  //   gPal = CRGBPalette16( CRGB::Black, CRGB::Red, CRGB::White);

}

void loop()
{
  // Add entropy to random number generator; we use a lot of it.
  random16_add_entropy( random());

  // Fourth, the most sophisticated: this one sets up a new palette every
  // time through the loop, based on a hue that changes every time.
  // The palette is a gradient from black, to a dark color based on the hue,
  // to a light color based on the hue, to white.
  //
  //   static uint8_t hue = 0;
  //   hue++;
  //   CRGB darkcolor  = CHSV(hue,255,192); // pure hue, three-quarters brightness
  //   CRGB lightcolor = CHSV(hue,128,255); // half 'whitened', full brightness
  //   gPal = CRGBPalette16( CRGB::Black, darkcolor, lightcolor, CRGB::White);


  Fire2012WithPalette(); // run simulation frame, using palette colors
  
  FastLED.show(); // display this frame
  FastLED.delay(1000 / FRAMES_PER_SECOND);
}


// Fire2012 by Mark Kriegsman, July 2012
// as part of "Five Elements" shown here: http://youtu.be/knWiGsmgycY
////
// This basic one-dimensional 'fire' simulation works roughly as follows:
// There's a underlying array of 'heat' cells, that model the temperature
// at each point along the line.  Every cycle through the simulation,
// four steps are performed:
//  1) All cells cool down a little bit, losing heat to the air
//  2) The heat from each cell drifts 'up' and diffuses a little
//  3) Sometimes randomly new 'sparks' of heat are added at the bottom
//  4) The heat from each cell is rendered as a color into the leds array
//     The heat-to-color mapping uses a black-body radiation approximation.
//
// Temperature is in arbitrary units from 0 (cold black) to 255 (white hot).
//
// This simulation scales it self a bit depending on NUM_LEDS; it should look
// "OK" on anywhere from 20 to 100 LEDs without too much tweaking.
//
// I recommend running this simulation at anywhere from 30-100 frames per second,
// meaning an interframe delay of about 10-35 milliseconds.
//
// Looks best on a high-density LED setup (60+ pixels/meter).
//
//
// There are two main parameters you can play with to control the look and
// feel of your fire: COOLING (used in step 1 above), and SPARKING (used
// in step 3 above).
//
// COOLING: How much does the air cool as it rises?
// Less cooling = taller flames.  More cooling = shorter flames.
// Default 55, suggested range 20-100
#define COOLING  55

// SPARKING: What chance (out of 255) is there that a new spark will be lit?
// Higher chance = more roaring fire.  Lower chance = more flickery fire.
// Default 120, suggested range 50-200.
#define SPARKING 120


void Fire2012WithPalette()
{
// Array of temperature readings at each simulation cell
  static uint8_t heat[NUM_LEDS];

  // Step 1.  Cool down every cell a little
    for( int i = 0; i < NUM_LEDS; i++) {
      heat[i] = qsub8( heat[i],  random8(0, ((COOLING * 10) / NUM_LEDS) + 2));
    }
  
    // Step 2.  Heat from each cell drifts 'up' and diffuses a little
    for( int k= NUM_LEDS - 1; k >= 2; k--) {
      heat[k] = (heat[k - 1] + heat[k - 2] + heat[k - 2] ) / 3;
    }
   
    // Step 3.  Randomly ignite new 'sparks' of heat near the bottom
    if( random8() < SPARKING ) {
      int y = random8(7);
      heat[y] = qadd8( heat[y], random8(160,255) );
    }

    // Step 4.  Map from heat cells to LED colors
    for( int j = 0; j < NUM_LEDS; j++) {
      // Scale the heat value from 0-255 down to 0-240
      // for best results with color palettes.
      uint8_t colorindex = scale8( heat[j], 240);
      CRGB color = ColorFromPalette( gPal, colorindex);
      int pixelnumber;
      if( gReverseDirection ) {
        pixelnumber = (NUM_LEDS-1) - j;
      } else {
        pixelnumber = j;
      }
      leds[pixelnumber] = color;
    }
}
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实验场景  动态图

  【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812灯板
  实验程序五：FastLED的八种动态颜色的配色板

/*
  【花雕体验】16 使用Beetle ESP32 C3控制8X32位WS2812灯板
  实验程序五：FastLED的八种动态颜色的配色板
*/

#include <FastLED.h>

#define LED_PIN     6
#define NUM_LEDS    256
#define BRIGHTNESS  22
#define LED_TYPE    WS2811
#define COLOR_ORDER GRB
CRGB leds[NUM_LEDS];

#define UPDATES_PER_SECOND 100 //定义每秒更新数

// This example shows several ways to set up and use 'palettes' of colors
// with FastLED.
//
// These compact palettes provide an easy way to re-colorize your
// animation on the fly, quickly, easily, and with low overhead.
//
// USING palettes is MUCH simpler in practice than in theory, so first just
// run this sketch, and watch the pretty lights as you then read through
// the code.  Although this sketch has eight (or more) different color schemes,
// the entire sketch compiles down to about 6.5K on AVR.
//
// FastLED provides a few pre-configured color palettes, and makes it
// extremely easy to make up your own color schemes with palettes.
//
// Some notes on the more abstract 'theory and practice' of
// FastLED compact palettes are at the bottom of this file.



CRGBPalette16 currentPalette;
TBlendType    currentBlending;

extern CRGBPalette16 myRedWhiteBluePalette;
extern const TProgmemPalette16 myRedWhiteBluePalette_p PROGMEM;


void setup() {
    delay( 3000 ); // power-up safety delay
    FastLED.addLeds<LED_TYPE, LED_PIN, COLOR_ORDER>(leds, NUM_LEDS).setCorrection( TypicalLEDStrip );
    FastLED.setBrightness(  BRIGHTNESS );
    currentPalette = RainbowColors_p;
    currentBlending = LINEARBLEND;
}


void loop(){
    ChangePalettePeriodically();
   
    static uint8_t startIndex = 0;
    startIndex = startIndex + 1; /* motion speed */
   
    FillLEDsFromPaletteColors( startIndex);
   
    FastLED.show();
    FastLED.delay(1000 / UPDATES_PER_SECOND);
}

void FillLEDsFromPaletteColors( uint8_t colorIndex)
{
    uint8_t brightness = 255;
   
    for( int i = 0; i < NUM_LEDS; ++i) {
        leds[i] = ColorFromPalette( currentPalette, colorIndex, brightness, currentBlending);
        colorIndex += 3;
    }
}


// There are several different palettes of colors demonstrated here.
//
// FastLED provides several 'preset' palettes: RainbowColors_p, RainbowStripeColors_p,
// OceanColors_p, CloudColors_p, LavaColors_p, ForestColors_p, and PartyColors_p.
//
// Additionally, you can manually define your own color palettes, or you can write
// code that creates color palettes on the fly.  All are shown here.

void ChangePalettePeriodically()
{
    uint8_t secondHand = (millis() / 1000) % 60;
    static uint8_t lastSecond = 99;
   
    if( lastSecond != secondHand) {
        lastSecond = secondHand;
        if( secondHand ==  0)  { currentPalette = RainbowColors_p;         currentBlending = LINEARBLEND; }
        if( secondHand == 10)  { currentPalette = RainbowStripeColors_p;   currentBlending = NOBLEND;  }
        if( secondHand == 15)  { currentPalette = RainbowStripeColors_p;   currentBlending = LINEARBLEND; }
        if( secondHand == 20)  { SetupPurpleAndGreenPalette();             currentBlending = LINEARBLEND; }
        if( secondHand == 25)  { SetupTotallyRandomPalette();              currentBlending = LINEARBLEND; }
        if( secondHand == 30)  { SetupBlackAndWhiteStripedPalette();       currentBlending = NOBLEND; }
        if( secondHand == 35)  { SetupBlackAndWhiteStripedPalette();       currentBlending = LINEARBLEND; }
        if( secondHand == 40)  { currentPalette = CloudColors_p;           currentBlending = LINEARBLEND; }
        if( secondHand == 45)  { currentPalette = PartyColors_p;           currentBlending = LINEARBLEND; }
        if( secondHand == 50)  { currentPalette = myRedWhiteBluePalette_p; currentBlending = NOBLEND;  }
        if( secondHand == 55)  { currentPalette = myRedWhiteBluePalette_p; currentBlending = LINEARBLEND; }
    }
}

// This function fills the palette with totally random colors.
void SetupTotallyRandomPalette()
{
    for( int i = 0; i < 16; ++i) {
        currentPalette[i] = CHSV( random8(), 255, random8());
    }
}

// This function sets up a palette of black and white stripes,
// using code.  Since the palette is effectively an array of
// sixteen CRGB colors, the various fill_* functions can be used
// to set them up.
void SetupBlackAndWhiteStripedPalette()
{
    // 'black out' all 16 palette entries...
    fill_solid( currentPalette, 16, CRGB::Black);
    // and set every fourth one to white.
    currentPalette[0] = CRGB::White;
    currentPalette[4] = CRGB::White;
    currentPalette[8] = CRGB::White;
    currentPalette[12] = CRGB::White;
   
}

// This function sets up a palette of purple and green stripes.
void SetupPurpleAndGreenPalette()
{
    CRGB purple = CHSV( HUE_PURPLE, 255, 255);
    CRGB green  = CHSV( HUE_GREEN, 255, 255);
    CRGB black  = CRGB::Black;
   
    currentPalette = CRGBPalette16(
                                   green,  green,  black,  black,
                                   purple, purple, black,  black,
                                   green,  green,  black,  black,
                                   purple, purple, black,  black );
}


// This example shows how to set up a static color palette
// which is stored in PROGMEM (flash), which is almost always more
// plentiful than RAM.  A static PROGMEM palette like this
// takes up 64 bytes of flash.
const TProgmemPalette16 myRedWhiteBluePalette_p PROGMEM =
{
    CRGB::Red,
    CRGB::Gray, // 'white' is too bright compared to red and blue
    CRGB::Blue,
    CRGB::Black,
   
    CRGB::Red,
    CRGB::Gray,
    CRGB::Blue,
    CRGB::Black,
   
    CRGB::Red,
    CRGB::Red,
    CRGB::Gray,
    CRGB::Gray,
    CRGB::Blue,
    CRGB::Blue,
    CRGB::Black,
    CRGB::Black
};

// Additional notes on FastLED compact palettes:
//
// Normally, in computer graphics, the palette (or "color lookup table")
// has 256 entries, each containing a specific 24-bit RGB color.  You can then
// index into the color palette using a simple 8-bit (one byte) value.
// A 256-entry color palette takes up 768 bytes of RAM, which on Arduino
// is quite possibly "too many" bytes.
//
// FastLED does offer traditional 256-element palettes, for setups that
// can afford the 768-byte cost in RAM.
//
// However, FastLED also offers a compact alternative.  FastLED offers
// palettes that store 16 distinct entries, but can be accessed AS IF
// they actually have 256 entries; this is accomplished by interpolating
// between the 16 explicit entries to create fifteen intermediate palette
// entries between each pair.
//
// So for example, if you set the first two explicit entries of a compact
// palette to Green (0,255,0) and Blue (0,0,255), and then retrieved
// the first sixteen entries from the virtual palette (of 256), you'd get
// Green, followed by a smooth gradient from green-to-blue, and then Blue.
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实验的视频记录（67秒）

https://v.youku.com/v_show/id_XN ... hcb.playlsit.page.1