TFT_eSPI/examples/Sprite/Sprite_draw_4bit/Sprite_draw_4bit.ino

/*
  Sketch to show how a 4 bit Sprite is created, how to draw pixels
  and text within the Sprite and then push the Sprite onto
  the display screen.

  The advantage of 4 bit sprites is:
    1. Small memory footprint
    2. Any set of 16 colours can be specified
    3. Colours can be changed without redrawing in Sprite
    4. Simple animations like flashing text can be achieved
       by colour palette cycling and pushing sprite to TFT:
       https://en.wikipedia.org/wiki/Color_cycling

  Example for library:
  https://github.com/Bodmer/TFT_eSPI

  A Sprite is notionally an invisible graphics screen that is
  kept in the processors RAM. Graphics can be drawn into the
  Sprite just as it can be drawn directly to the screen. Once
  the Sprite is completed it can be plotted onto the screen in
  any position. If there is sufficient RAM then the Sprite can
  be the same size as the screen and used as a frame buffer.

  A 4 bit Sprite occupies (width * height)/2 bytes in RAM.

*/

// Set delay after plotting the sprite
#define DELAY 1000

// Width and height of sprite
#define WIDTH  128
#define HEIGHT 128

#include <TFT_eSPI.h>                 // Include the graphics library (this includes the sprite functions)

TFT_eSPI    tft = TFT_eSPI();         // Declare object "tft"

TFT_eSprite spr = TFT_eSprite(&tft);  // Declare Sprite object "spr" with pointer to "tft" object


void setup()
{
  Serial.begin(115200);
  Serial.println();

  delay(500);

  // Initialise the TFT registers
  tft.init();

  // Set the sprite colour depth to 4
  spr.setColorDepth(4);

  // Create a sprite of defined size
  spr.createSprite(WIDTH, HEIGHT);

  // Clear the TFT screen to blue
  tft.fillScreen(TFT_BLUE);
}

void loop(void)
{
  // Fill the whole sprite with color 0 (Sprite is in memory so not visible yet)
  spr.fillSprite(0);

   // create a color map with known colors (16 maximum for 4 bit Sprite
  uint16_t cmap[16];


  cmap[0]  = TFT_BLACK; // We will keep this as black
  cmap[1]  = TFT_NAVY;
  cmap[2]  = TFT_DARKGREEN;
  cmap[3]  = TFT_DARKCYAN;
  cmap[4]  = TFT_MAROON;
  cmap[5]  = TFT_PURPLE;
  cmap[6]  = TFT_PINK;
  cmap[7]  = TFT_LIGHTGREY;
  cmap[8]  = TFT_YELLOW;
  cmap[9]  = TFT_BLUE;
  cmap[10] = TFT_GREEN;
  cmap[11] = TFT_CYAN;
  cmap[12] = TFT_RED;
  cmap[13] = TFT_MAGENTA;
  cmap[14] = TFT_WHITE;  // Keep as white for text
  cmap[15] = TFT_BLUE;   // Keep as blue for sprite border

  // Pass the palette to the Sprite class
  spr.createPalette(cmap);

  // Push Sprite parially off-screen to test cropping
  spr.pushSprite(-40, -40);
  spr.pushSprite(tft.width() / 2 - WIDTH / 2, tft.height() / 2 - HEIGHT / 2, 10);
  spr.pushSprite(tft.width() - WIDTH + 40, tft.height() - HEIGHT + 40);

  // Number of pixels to draw
  uint16_t n = 100;

  // Draw 100 random color pixels at random positions in sprite
  while (n--)
  {
    uint16_t color = random(0x10); // Returns color 0 - 0x0F (i.e. 0-15)
    int16_t x = random(WIDTH);     // Random x coordinate
    int16_t y = random(HEIGHT);    // Random y coordinate
    spr.drawPixel(x, y, color);    // Draw pixel in sprite
  }

  // Draw some lines
  spr.drawLine(1, 0, WIDTH, HEIGHT-1, 10);
  spr.drawLine(0, 0, WIDTH, HEIGHT, 10);
  spr.drawLine(0, 1, WIDTH-1, HEIGHT, 10);
  spr.drawLine(0, HEIGHT-1, WIDTH-1, 0, 12);
  spr.drawLine(0, HEIGHT, WIDTH, 0, 12);
  spr.drawLine(1, HEIGHT, WIDTH, 1, 12);

 // Draw some text with Middle Centre datum
  spr.setTextDatum(MC_DATUM);
  spr.setTextColor(14); // White text
  spr.drawString("Sprite", WIDTH / 2, HEIGHT / 2, 4);

  // Now push the sprite to the TFT at 3 positions on screen
  spr.pushSprite(-40, -40);
  spr.pushSprite(tft.width() / 2 - WIDTH / 2, tft.height() / 2 - HEIGHT / 2);
  spr.pushSprite(tft.width() - WIDTH + 40, tft.height() - HEIGHT + 40);

  delay(DELAY * 4);

  // create a new color map for colours 1-13 and use it instead
  for (auto i = 1; i <= 13; i++)
  {
    cmap[i] = random(0x10000);
  }

  spr.createPalette(cmap, 16);
  // Now push the sprite to the TFT at position 0,0 on screen

  spr.pushSprite(-40, -40);
  spr.pushSprite(tft.width() / 2 - WIDTH / 2, tft.height() / 2 - HEIGHT / 2);
  spr.pushSprite(tft.width() - WIDTH + 40, tft.height() - HEIGHT + 40);

  delay(DELAY);

    // Fill TFT screen with blue
  tft.fillScreen(TFT_BLUE);

  // Draw a blue rectangle in sprite so when we move it 1 pixel it does not leave a trail
  // on the blue screen background
  spr.createPalette(cmap);

  spr.drawRect(0, 0, WIDTH, HEIGHT, 15); // Blue rectangle

  int x = tft.width() / 2  -  WIDTH / 2;
  int y = tft.height() / 2 - HEIGHT / 2;

  uint32_t updateTime = 0;       // time for next update

  while (true)
  {
    // Random movement direction
    int dx = 1; if (random(2)) dx = -1;
    int dy = 1; if (random(2)) dy = -1;

    // Pull it back onto screen if it wanders off
    if (x < -WIDTH/2) dx = 1;
    if (x >= tft.width()-WIDTH/2) dx = -1;
    if (y < -HEIGHT/2) dy = 1;
    if (y >= tft.height()-HEIGHT/2) dy = -1;

    // Randomise the palette to change colours without redrawing
    // the sprite
    for (auto i = 1; i <= 13; i++)
    {
      cmap[i] = random(0x10000);
    }
    spr.createPalette(cmap); // Update sprite class palette

    // Draw it 50 times, moving in random direct or staying still
    n = 50;
    int wait = random (50);
    while (n)
    {
      if (updateTime <= millis())
      {
        // Use time delay so sprite does not move fast when not all on screen
        updateTime = millis() + wait;

        // Push the sprite to the TFT screen
          spr.pushSprite(x, y);

        // Change coord for next loop
        x += dx;
        y += dy;
        n--;
        yield(); // Stop watchdog reset
      }
    }
  } // Infinite while, will not exit!
}