Add 1 bpp examples

examples/Sprite/1_bit_Sprite_Demo/1_bit_Sprite_Demo.ino

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+/*
+  Sketch to show creation of a 1bpp sprite with a transparent
+  background, then plot it on the TFT.
+
+  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 1 bit Sprite occupies (width * height)/8 bytes in RAM. So,
+  for example, a 320 x 240 pixel Sprite occupies 9600 bytes.
+*/
+// A new setBitmapColor(fg_color, bg_color) function allows
+// any 2 colours to be used for the 1 bit sprite.
+// One colour can also be defined as transparent when
+// rendering to the screen.
+
+
+#include <TFT_eSPI.h>                 // Include the graphics library (this includes the sprite functions)
+
+TFT_eSPI    tft = TFT_eSPI();         // Create object "tft"
+
+TFT_eSprite img = TFT_eSprite(&tft);  // Create Sprite object "img" with pointer to "tft" object
+                                      // the pointer is used by pushSprite() to push it onto the TFT
+
+#define BITS_PER_PIXEL 1              // How many bits per pixel in Sprite
+
+// =========================================================================
+void setup(void) {
+  Serial.begin(250000);
+
+  tft.init();
+
+  tft.setRotation(0);
+}
+// =========================================================================
+void loop() {
+
+  tft.fillScreen(TFT_NAVY);
+
+  // Draw 10 sprites containing a "transparent" colour
+  for (int i = 0; i < 10; i++)
+  {
+    int x = random(240 - 70);
+    int y = random(320 - 80);
+    int c = random(0x10000); // Random colour 0 - 0xFFFF
+    drawStar(x, y, c);
+  }
+
+  delay(2000);
+
+  // Now go bananas and draw 500 more
+  for (int i = 0; i < 500; i++)
+  {
+    int x = random(240 - 70);
+    int y = random(320 - 80);
+    int c = random(0x10000); // Random colour
+    drawStar(x, y, c);
+    yield(); // Stop watchdog reset
+  }
+
+  delay(2000);
+}
+// =========================================================================
+// Create sprite, plot graphics in it, plot to screen, then delete sprite
+// =========================================================================
+void drawStar(int x, int y, int star_color)
+{
+  // 1 bpp colour values can only be 1 or 0 (one or zero)
+  uint16_t transparent = 0; // The transparent colour, can only be 1 or 0
+
+  // Create an 1 bit (2 colour) sprite 70x80 pixels (uses 70*80/8 = 700 bytes of RAM)
+  // Colour depths of 8 bits per pixel and 16 bits are also supported.
+  img.setColorDepth(BITS_PER_PIXEL);         // Set colour depth first
+  img.createSprite(70, 80);                  // then create the sprite
+
+  // Fill Sprite with the colour that will be defined later as "transparent"
+  // We could also fill with any colour as transparent, and later specify that
+  // same colour when we push the Sprite onto the display screen.
+  img.fillSprite(transparent);
+
+  // Draw 2 triangles to create a filled in star
+  img.fillTriangle(35, 0, 0, 59, 69, 59, star_color);
+  img.fillTriangle(35, 79, 0, 20, 69, 20, star_color);
+
+  // Punch a star shaped hole in the middle with a smaller "transparent" star
+  img.fillTriangle(35, 7, 6, 56, 63, 56, transparent);
+  img.fillTriangle(35, 73, 6, 24, 63, 24, transparent);
+
+  // Set the 2 pixel colours that 1 and 0 represent on the display screen
+  img.setBitmapColor(star_color, transparent);
+
+  // Push sprite to TFT screen CGRAM at coordinate x,y (top left corner)
+  // Specify what colour is to be treated as transparent (black in this example)
+  img.pushSprite(x, y, transparent);
+
+  // Delete Sprite to free memory, creating and deleting takes very little time.
+  img.deleteSprite();
+}
+// =========================================================================
+

examples/Sprite/1_bit_Yin_Yang/1_bit_Yin_Yang.ino

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+// This sketch draws a rotating Yin and Yang symbol. It illustrates
+// the drawimg and rendering of simple animated graphics using
+// a 1 bit per pixel (1 bpp) Sprite.
+
+// Note:  TFT_BLACK sets the pixel value to 0
+// Any other colour sets the pixel value to 1
+
+// A square sprite of side = 2 x RADIUS will be created
+// (80 * 80)/8 = 800 bytes needed for 1 bpp sprite
+//              6400 bytes for 8 bpp
+//             12800 bytes for 16 bpp
+#define RADIUS 40      // Radius of completed symbol = 40
+
+#define WAIT 0         // Loop delay
+
+// 1bpp Sprites are economical on memory but slower to render
+#define COLOR_DEPTH 1  // Colour depth (1, 8 or 16 bits per pixel)
+
+// Rotation angle increment and start angle
+#define ANGLE_INC 3
+int angle = 0;
+
+#include <TFT_eSPI.h>                 // Hardware-specific library
+
+TFT_eSPI    tft = TFT_eSPI();         // Invoke library
+
+TFT_eSprite img = TFT_eSprite(&tft);  // Sprite class
+
+
+// -------------------------------------------------------------------------
+void setup(void)
+{
+  tft.begin();
+  tft.setRotation(0);
+  tft.fillScreen(TFT_BLUE);
+
+  img.setColorDepth(COLOR_DEPTH);
+  img.createSprite(RADIUS*2+1, RADIUS*2+1);
+  img.fillSprite(TFT_BLACK);
+}
+// -------------------------------------------------------------------------
+// -------------------------------------------------------------------------
+void loop() {
+  // Draw Yin and Yang symbol circles into Sprite
+  yinyang(RADIUS, RADIUS, angle, RADIUS);
+
+  // Set the 2 pixel palette colours that 1 and 0 represent on the display screen
+  img.setBitmapColor(TFT_WHITE, TFT_BLACK); 
+
+  // Push Sprite image to the TFT screen at x, y
+  img.pushSprite(tft.width()/2 - RADIUS, 0); // Plot sprite
+
+  angle+=3;                   //Increment angle to rotate circle positions
+  if (angle > 359) angle = 0; // Limit angle range
+
+  // Slow things down
+  delay(WAIT);
+}
+// -------------------------------------------------------------------------
+
+
+// =========================================================================
+// Draw circles for Yin and Yang - rotate positions to create symbol
+// =========================================================================
+// x,y == coordinate center within Sprite
+// start_angle = 0 - 359
+// r = radius
+
+int yinyang(int x, int y, int start_angle, int r)
+{
+  int x1 = 0; // getCoord() will update these
+  int y1 = 0;
+
+  getCoord(x, y, &x1, &y1, r/2, start_angle); // Get x1 ,y1
+  img.fillCircle( x1,  y1, r/2, TFT_WHITE);
+  img.fillCircle( x1,  y1, r/8, TFT_BLACK);
+
+  getCoord(x, y, &x1, &y1, r/2, start_angle + 180);
+  img.fillCircle( x1,  y1, r/2, TFT_BLACK);
+  img.fillCircle( x1,  y1, r/8, TFT_WHITE);
+  
+  img.drawCircle(x, y, r, TFT_WHITE);
+}
+
+// =========================================================================
+// Get coordinates of end of a vector, pivot at x,y, length r, angle a
+// =========================================================================
+// Coordinates are returned to caller via the xp and yp pointers
+#define RAD2DEG 0.0174532925
+void getCoord(int x, int y, int *xp, int *yp, int r, int a)
+{
+  float sx1 = cos( (a-90) * RAD2DEG );    
+  float sy1 = sin( (a-90) * RAD2DEG );
+  *xp =  sx1 * r + x;
+  *yp =  sy1 * r + y;
+}
+