finally ported the moire pattern from cyberleiber to master

src/animations/Makefile

@@ -30,6 +30,10 @@ ifeq ($(ANIMATION_MHERWEG),y)
   SRC += mherweg.c
 endif
 
+ifeq ($(ANIMATION_MOIRE),y)
+  SRC += moire.c
+endif
+
 ifeq ($(ANIMATION_BREAKOUT),y)
   SRC += breakout_demo.c
 endif

src/animations/config.in

@@ -42,6 +42,7 @@ comment "Animations"
 
 	dep_bool "Breakout Demo" ANIMATION_BREAKOUT      $GAME_BREAKOUT
 	dep_bool "Martin Herweg" ANIMATION_MHERWEG       $RANDOM_SUPPORT
+	dep_bool "Moire"         ANIMATION_MOIRE         $RANDOM_SUPPORT
 	dep_bool "Langton Ant"   ANIMATION_LTN_ANT       $RANDOM_SUPPORT
 
 	dep_bool_menu "Time Display"  ANIMATION_TIME $SCROLLTEXT_SUPPORT $LAP_TIME_EXTENSION

src/animations/mherweg.c

@@ -27,51 +27,6 @@
 #define PGM(x) pgm_read_byte(&(x))
 
 
-#if NUM_ROWS < 64 && NUM_COLS < 64
-	/** use 8 bit operands where feasible */
-	typedef signed char operand_t;
-#else
-	/** use 16 bit operands if either width or height are >= 64 */
-	typedef int operand_t;
-#endif
-
-
-/**
- * An implementation of Bresenham's line drawing algorithm.
- * @param p1 first coordinate of the line
- * @param p2 second coordinate of the line
- * @param color brightness level of the line
- */
-static void line(pixel p1,
-                 pixel const p2,
-                 unsigned char const color)
-{
-	operand_t const dx = p1.x < p2.x ? p2.x - p1.x : p1.x - p2.x;
-	operand_t const sx = p1.x < p2.x ? 1 : -1;
-	operand_t const dy = p1.y < p2.y ? p2.y - p1.y : p1.y - p2.y;
-	operand_t const sy = p1.y < p2.y ? 1 : -1;
-	operand_t error = dx - dy;
-
-	while(1)
-	{
-		setpixel(p1, color);
-		if ((p1.x == p2.x) && (p1.y == p2.y))
-			break;
-		operand_t const error2 = 2 * error;
-		if (error2 > -dy)
-		{
-			error -= dy;
-			p1.x += sx;
-		}
-		if (error2 < dx)
-		{
-			error += dx;
-			p1.y += sy;
-		}
-	}
-}
-
-
 /**
  * Draws a rectangle at the given coordinates.
  * @param p coordinate of the rectangle's upper right corner

src/animations/moire.c

@@ -0,0 +1,88 @@
+/**
+ * \defgroup moire A moire like pattern.
+ * @{
+ */
+
+/**
+ * @file moire.c
+ * @brief Implementation of a simple moire like pattern.
+ * @author Christian Kroll
+ */
+
+#include "../config.h"
+#include "../pixel.h"
+#include "../util.h"
+
+/**
+ * Number of pixels of the complete border.
+ */
+#define NUMBER_OF_BORDER_PIXELS (2u * UNUM_COLS + 2u * (UNUM_ROWS - 2u))
+
+/**
+ * Draws a moire like pattern. Works best if the number of border pixels is a
+ * multiple of the size of the gradient color map.
+ */
+void moire(void)
+{
+	// add rotating color map
+#if NUMPLANE == 3
+	static unsigned char const gradient[] = {0, 1, 2, 3, 2, 1};
+#else
+	static unsigned char gradient[NUMPLANE * 2u] = {0};
+	for (unsigned char i = 1; i <= NUMPLANE; ++i)
+	{
+		gradient[i] = i;
+		gradient[(NUMPLANE * 2) - i] = i;
+	}
+#endif
+
+	unsigned int cycles = 30000;
+	unsigned char pos = 0, color_index = 0;
+	pixel p1 = (pixel){0 ,0};
+
+	while(cycles--)
+	{
+		// walk around the border; do that by mapping a linear increasing value
+		// to appropriate screen coordinates
+
+		// first pixel is between top right and top left corner
+		if (pos < NUM_COLS)
+		{
+			p1.x = pos;
+		}
+		// first pixel is between top left and bottom left corner
+		else if (pos < (NUM_COLS + NUM_ROWS - 1))
+		{
+			p1.y = pos - (NUM_COLS - 1);
+		}
+		// first pixel is between bottom left and bottom right corner
+		else if (pos < (2 * NUM_COLS + NUM_ROWS - 2))
+		{
+			p1.x = 2 * NUM_COLS + NUM_ROWS - 3 - pos;
+		}
+		// first pixel is between bottom right and top left corner
+		else
+		{
+			p1.y = 3 * NUM_COLS + NUM_ROWS - 4 - pos;
+		}
+
+		// second pixel in opposite direction
+		pixel const p2 = (pixel){NUM_COLS - 1 - p1.x, NUM_ROWS - 1 - p1.y};
+
+		// draw line right accross the display and switch to next color
+		line(p1, p2, gradient[color_index++]);
+
+		// if we have reached the origin, reset position, rotate color index and
+		// wait for 40 ms (25 fps) to make the frame visible for human viewers
+		if (++pos == NUMBER_OF_BORDER_PIXELS)
+		{
+			pos = 0;
+			++color_index;
+			wait(40);
+		}
+		// ensure the color index keeps within bounds
+		color_index %= (2u * NUMPLANE);
+	}
+}
+
+/*@}*/

src/animations/moire.h

@@ -0,0 +1,19 @@
+/**
+ * \defgroup moire A moire like pattern.
+ * @{
+ */
+
+/**
+ * @file moire.h
+ * @brief Interface file for a moire pattern implementation.
+ * @author Christian Kroll
+ */
+
+#ifndef MOIRE_H_
+#define MOIRE_H_
+
+void moire(void);
+
+#endif /* MOIRE_H_ */
+
+/*@}*/

src/display_loop.c

@@ -18,6 +18,7 @@
 #include "animations/bitmapscroller/fairydust.h"
 #include "animations/fpmath_patterns.h"
 #include "animations/mherweg.h"
+#include "animations/moire.h"
 #include "animations/blackhole.h"
 #include "animations/squares.h"
 #ifdef ANIMATION_TIME
@@ -183,62 +184,68 @@ void display_loop(){
 			break;
 #endif
 
-#ifdef ANIMATION_TIME
+#ifdef ANIMATION_MOIRE
 		case 15:
+			moire();
+			break;
+#endif
+
+#ifdef ANIMATION_TIME
+		case 16:
 			time_anim();
 			break;
 #endif
 
 #ifdef ANIMATION_LTN_ANT
-		case 16:
+		case 17:
 			ltn_ant();
 			break;
 #endif
 
 #ifdef ANIMATION_LABORLOGO
-		case 17:
+		case 18:
 			laborlogo();
 			break;
 #endif
 
 #ifdef ANIMATION_AMPHIBIAN
-		case 18:
+		case 19:
 			amphibian();
 			break;
 #endif
 
 #ifdef ANIMATION_LOGO_OOS
-		case 19:
+		case 20:
 			logo_OutOfSpec();
 			break;
 #endif
 
 #ifdef ANIMATION_FAIRYDUST
-		case 20:
+		case 21:
 			fairydust();
 			break;
 #endif
 
 #ifdef ANIMATION_PLASMA
-		case 21:
+		case 22:
 			plasma();
 			break;
 #endif
 
 #ifdef ANIMATION_PSYCHEDELIC
-		case 22:
+		case 23:
 			psychedelic();
 			break;
 #endif
 
 #ifdef ANIMATION_BLACKHOLE
-		case 23:
+		case 24:
 			blackhole();
 			break;
 #endif
 
 #ifdef ANIMATION_SQUARES
-		case 24:
+		case 25:
 			squares();
 			break;
 #endif

src/pixel.c

@@ -58,3 +58,38 @@ unsigned char get_pixel(pixel p){
 		return 0!= (pixmap[0][p.y][p.x/8] & shl_table[p.x%8]);
 	}
 }
+
+/**
+ * An implementation of Bresenham's line drawing algorithm.
+ * @param p1 first coordinate of the line
+ * @param p2 second coordinate of the line
+ * @param color brightness level of the line
+ */
+void line(pixel p1,
+          pixel const p2,
+          unsigned char const color)
+{
+	operand_t const dx = p1.x < p2.x ? p2.x - p1.x : p1.x - p2.x;
+	operand_t const sx = p1.x < p2.x ? 1 : -1;
+	operand_t const dy = p1.y < p2.y ? p2.y - p1.y : p1.y - p2.y;
+	operand_t const sy = p1.y < p2.y ? 1 : -1;
+	operand_t error = dx - dy;
+
+	while(1)
+	{
+		setpixel(p1, color);
+		if ((p1.x == p2.x) && (p1.y == p2.y))
+			break;
+		operand_t const error2 = 2 * error;
+		if (error2 > -dy)
+		{
+			error -= dy;
+			p1.x += sx;
+		}
+		if (error2 < dx)
+		{
+			error += dx;
+			p1.y += sy;
+		}
+	}
+}

src/pixel.h

@@ -42,6 +42,15 @@ typedef struct cursor{
 	pixelmode_t mode;
 } cursor_t;
 
+
+#if NUM_ROWS < 64 && NUM_COLS < 64
+	/** use 8 bit operands where feasible */
+	typedef signed char operand_t;
+#else
+	/** use 16 bit operands if either width or height are >= 64 */
+	typedef int operand_t;
+#endif
+
 /****************************************************************************
  * Pixel routines
  */
@@ -79,4 +88,8 @@ static inline void set_cursor(cursor_t* cur, pixel p){
 	setpixel(p, cur->mode ? 3 : 0);
 }
 
+void line(pixel p1,
+          pixel const p2,
+          unsigned char const color);
+
 #endif // PIXEL_H