Implement anti-aliasing in the NuttX graphics line drawing

graphics/Kconfig

@@ -39,6 +39,14 @@ config NX_BGCOLOR
 		logic would have to be extended if you want to support multiple
 		color planes.
 
+config NX_ANTIALIASING
+	bool "Anti-aliasing support"
+	default n
+	depends on (!NX_DISABLE_16BPP || !NX_DISABLE_24BPP || !NX_DISABLE_32BPP) && !NX_LCDDRIVER
+	---help---
+		Enable support for ant-alising when rendering lines as various
+		orientations.
+
 config NX_WRITEONLY
 	bool "Write-only Graphics Device"
 	default y if NX_LCDDRIVER && LCD_NOGETRUN

graphics/nxglib/fb/nxglib_filltrapezoid.c

@@ -1,7 +1,7 @@
 /****************************************************************************
  * graphics/nxglib/fb/nxglib_filltrapezoid.c
  *
- *   Copyright (C) 2008-2012 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2008-2012, 2015 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -50,27 +50,12 @@
 /****************************************************************************
  * Pre-processor Definitions
  ****************************************************************************/
+/* Make sure that this file is used in the proper context */
 
 #ifndef NXGLIB_SUFFIX
 #  error "NXGLIB_SUFFIX must be defined before including this header file"
 #endif
 
-/****************************************************************************
- * Private Types
- ****************************************************************************/
-
-/****************************************************************************
- * Private Data
- ****************************************************************************/
-
-/****************************************************************************
- * Public Data
- ****************************************************************************/
-
-/****************************************************************************
- * Private Functions
- ****************************************************************************/
-
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -191,6 +176,9 @@ void NXGL_FUNCNAME(nxgl_filltrapezoid,NXGLIB_SUFFIX)(
 
   while (nrows--)
     {
+#ifdef CONFIG_NX_ANTIALIASING
+      b16_t frac;
+#endif
       int ix1;
       int ix2;
 
@@ -265,12 +253,43 @@ void NXGL_FUNCNAME(nxgl_filltrapezoid,NXGLIB_SUFFIX)(
               NXGL_MEMSET(dest, (NXGL_PIXEL_T)color, lnlen);
             }
 
-#else
+#else /* NXGLIB_BITSPERPIXEL < 8 */
+
           /* Then draw the run from (line + ix1) to (line + ix2) */
 
           dest = line + NXGL_SCALEX(ix1);
+
+#ifdef CONFIG_NX_ANTIALIASING
+
+          /* Perform blending on the first pixel of the row */
+
+          frac = b16ONE - b16frac(x1);
+          NXGL_BLEND(dest, (NXGL_PIXEL_T)color, frac);
+          dest += NXGL_SCALEX(1);
+          width--;
+
+          if (width > 0)
+            {
+              /* Copy pixels between the first and last pixel of the row. */
+
+              if (width > 1)
+                {
+                  NXGL_MEMSET(dest, (NXGL_PIXEL_T)color, width-1);
+                }
+
+              /* And blend the final pixel */
+
+              dest += NXGL_SCALEX(width-1);
+              frac  = b16frac(x2);
+              NXGL_BLEND(dest, (NXGL_PIXEL_T)color, frac);
+            }
+
+#else /* CONFIG_NX_ANTIALIASING */
+
           NXGL_MEMSET(dest, (NXGL_PIXEL_T)color, width);
-#endif
+
+#endif /* CONFIG_NX_ANTIALIASING */
+#endif /* NXGLIB_BITSPERPIXEL < 8 */
         }
 
       /* Move to the start of the next line */

graphics/nxglib/nxglib_bitblit.h

@@ -58,6 +58,13 @@
 #  error "NXGLIB_BITSPERPIXEL must be defined before including this header file"
 #endif
 
+/* Anti-aliasing can only be supported for 16-, 24-, and 32-bit RGB types */
+
+#if NXGLIB_BITSPERPIXEL < 16
+#  undef CONFIG_NX_ANTIALIASING
+#endif
+
+
 /* Set up bit blit macros for this BPP */
 
 #if NXGLIB_BITSPERPIXEL == 1
@@ -90,20 +97,24 @@
 
 #  define NXGL_SCALEX(x)           ((x) << 1)
 #  define NXGL_PIXEL_T             uint16_t
+#  define NXGL_BLENDER             nxglib_rgb565_blend
 
 #elif NXGLIB_BITSPERPIXEL == 24
 
 #  define NXGL_SCALEX(x)           (((x) << 1) + (x))
 #  define NXGL_PIXEL_T             uint32_t
+#  define NXGL_BLENDER             nxglib_rgb24_blend
 
 #elif NXGLIB_BITSPERPIXEL == 32
 
 #  define NXGL_SCALEX(x)           ((x) << 2)
 #  define NXGL_PIXEL_T             uint32_t
+#  define NXGL_BLENDER             nxglib_rgb24_blend
 
 #endif
 
 #if NXGLIB_BITSPERPIXEL < 8
+
 #  define NXGL_SCALEX(x)           ((x) >> NXGL_PIXELSHIFT)
 #  define NXGL_REMAINDERX(x)       ((x) & NXGL_PIXELMASK)
 #  define NXGL_ALIGNDOWN(x)        ((x) & ~NXGL_PIXELMASK)
@@ -118,6 +129,7 @@
          *_ptr++ = (value); \
        } \
    }
+
 #  define NXGL_MEMCPY(dest,src,width) \
    { \
      FAR uint8_t *_dptr = (FAR uint8_t*)(dest); \
@@ -130,6 +142,7 @@
    }
 
 #elif NXGLIB_BITSPERPIXEL == 24
+
 #  define NXGL_MEMSET(dest,value,width) \
    { \
      FAR uint8_t *_ptr  = (FAR uint8_t*)(dest); \
@@ -141,6 +154,7 @@
          *_ptr++ = (value) >> 16; \
        } \
    }
+
 #  define NXGL_MEMCPY(dest,src,width) \
    { \
      FAR uint8_t *_dptr = (FAR uint8_t*)(dest); \
@@ -153,7 +167,26 @@
          *_dptr++ = *_sptr++; \
        } \
    }
-#else
+
+#ifdef CONFIG_NX_ANTIALIASING
+
+#  define NXGL_BLEND(dest,color1,frac) \
+   { \
+     FAR uint8_t *_dptr = (FAR uint8_t*)(dest); \
+     uint32_t color2; \
+     uint32_t blend; \
+     color2 = ((uint32_t)_dptr[0] << 16) | \
+              ((uint32_t)_dptr[1] << 8) | \
+               (uint32_t)_dptr[2]; \
+     blend =  NXGL_BLENDER(color1, color2, frac); \
+     *_dptr++ = (blend >> 16) & 0xff; \
+     *_dptr++ = (blend >> 8)  & 0xff; \
+     *_dptr++ =  blend        & 0xff; \
+   }
+
+#endif /* CONFIG_NX_ANTIALIASING */
+#else /* NXGLIB_BITSPERPIXEL == 16 || NXGLIB_BITSPERPIXEL == 32 */
+
 #  define NXGL_MEMSET(dest,value,width) \
    { \
      FAR NXGL_PIXEL_T *_ptr = (FAR NXGL_PIXEL_T*)(dest); \
@@ -163,6 +196,7 @@
          *_ptr++ = (value); \
        } \
    }
+
 #  define NXGL_MEMCPY(dest,src,width) \
    { \
      FAR NXGL_PIXEL_T *_dptr = (FAR NXGL_PIXEL_T*)(dest); \
@@ -173,7 +207,18 @@
          *_dptr++ = *_sptr++; \
        } \
    }
-#endif
+
+#ifdef CONFIG_NX_ANTIALIASING
+
+#  define NXGL_BLEND(dest,color1,frac) \
+   { \
+     FAR NXGL_PIXEL_T *_dptr = (FAR NXGL_PIXEL_T*)(dest); \
+     NXGL_PIXEL_T color2 = *_dptr; \
+     *_dptr = NXGL_BLENDER(color1, color2, frac); \
+   }
+
+#endif /* CONFIG_NX_ANTIALIASING */
+#endif /* NXGLIB_BITSPERPIXEL */
 
 /* Form a function name by concatenating two strings */