added color maps and examples

Extensions/Sprite.h

@@ -32,11 +32,14 @@ class TFT_eSprite : public TFT_eSPI {
            // Returns a pointer to the Sprite frame buffer
   void*    frameBuffer(int8_t f);
   
-           // Set or get the colour depth to 8 or 16 bits. Can be used to change depth an existing
+           // Set or get the colour depth to 4, 8 or 16 bits. Can be used to change depth an existing
            // sprite, but clears it to black, returns a new pointer if sprite is re-created.
   void*    setColorDepth(int8_t b);
   int8_t   getColorDepth(void);
 
+           // Set the colour map for a 4 bit depth sprite.  Only the first 16 colours in the map are used.
+  void     setColorMap(uint16_t *colorMap, int colors);
+
            // Set foreground and background colours for 1 bit per pixel Sprite
   void     setBitmapColor(uint16_t fg, uint16_t bg);
 
@@ -100,7 +103,10 @@ class TFT_eSprite : public TFT_eSPI {
            // Read the colour of a pixel at x,y and return value in 565 format 
   uint16_t readPixel(int32_t x0, int32_t y0);
 
-           // Write an image (colour bitmap) to the sprite
+           // return the color map index of the pixel at x,y (used when scrolling)
+  uint8_t  cmapPixel(int32_t x, int32_t y);
+
+           // Write an image (colour bitmap) to the sprite.  Not implemented for _bpp == 4.
   void     pushImage(int32_t x0, int32_t y0, int32_t w, int32_t h, uint16_t *data);
   void     pushImage(int32_t x0, int32_t y0, int32_t w, int32_t h, const uint16_t *data);
 
@@ -141,9 +147,12 @@ class TFT_eSprite : public TFT_eSPI {
   uint8_t  _bpp;     // bits per pixel (1, 8 or 16)
   uint16_t *_img;    // pointer to 16 bit sprite
   uint8_t  *_img8;   // pointer to  8 bit sprite
+  uint8_t  *_img4;   // pointer to 4 bit sprite (uses color map)
   uint8_t  *_img8_1; // pointer to  frame 1
   uint8_t  *_img8_2; // pointer to  frame 2
 
+  uint16_t *_colorMap; // color map: 16 entries, used with 4 bit color map.
+
   int16_t _xpivot;   // x pivot point coordinate
   int16_t _ypivot;   // y pivot point coordinate