Add RGB blending logic needed to support anti-aliasing

include/fixedmath.h

@@ -121,6 +121,7 @@
 /* Conversions */
 
 #define b8toi(a)        ((a) >> 8)              /* Conversion to integer */
+#define ub8toi(a)       ((a) >> 8)              /* Conversion to unsigned integer */
 #define itob8(i)        (((b8_t)(i)) << 8)      /* Conversion from integer */
 #define uitoub8(i)      (((ub8_t)(i)) << 8)     /* Conversion from unsigned integer */
 #define b8tof(b)        (((float)b)/256.0)      /* Conversion to float */
@@ -152,6 +153,7 @@
 /* Conversions */
 
 #define b16toi(a)       ((a) >> 16)             /* Conversion to integer */
+#define ub16toi(a)      ((a) >> 16)             /* Conversion to unsgined integer */
 #define itob16(i)       (((b16_t)(i)) << 16)    /* Conversion from integer */
 #define uitoub16(i)     (((ub16_t)(i)) << 16)   /* Conversion from unsigned integer */
 #define b16tof(b)       (((float)b)/65536.0)    /* Conversion to float */

include/nuttx/nx/nxglib.h

@@ -745,6 +745,39 @@ void nxgl_circletraps(FAR const struct nxgl_point_s *center,
                       nxgl_coord_t radius,
                       FAR struct nxgl_trapezoid_s *circle);
 
+/****************************************************************************
+ * Name: nxglib_rgb24_blend and nxglib_rgb565_blend
+ *
+ * Description:
+ *   Blend a foreground color onto a background color.  This is *not* alpha
+ *   blending:  color2 is assumed to be opaque and "under" a semi-
+ *   transparent color1.
+ *
+ *   The frac1 value could be though as related to the 1/alpha value for
+ *   color1.  However, the background, color2, is always treated as though
+ *   alpha == 1.
+ *
+ *   This algorithm is used to handle endpoints as part of the
+ *   implementation of anti-aliasing without transparency.
+ *
+ * Input Parameters:
+ *   color1 - The semi-transparent, forground color
+ *   color2 - The opaque, background color
+ *   frac1  - The fractional amount of color1 to blend into color2
+ *
+ * Returned Value:
+ *   The blended color, encoded just was the input color1 and color2
+ *
+ ****************************************************************************/
+
+#if !defined(CONFIG_NX_DISABLE_24BPP) || !defined(CONFIG_NX_DISABLE_32BPP)
+uint32_t nxglib_rgb24_blend(uint32_t color1, uint32_t color2, ub16_t frac1);
+#endif
+
+#ifndef CONFIG_NX_DISABLE_16BPP
+uint16_t nxglib_rgb565_blend(uint16_t color1, uint16_t color2, ub16_t frac1);
+#endif
+
 #undef EXTERN
 #if defined(__cplusplus)
 }

libnx/nxglib/Make.defs

@@ -41,10 +41,10 @@ CSRCS += nxglib_circlepts.c nxglib_circletraps.c nxglib_intersecting.c
 CSRCS += nxglib_nonintersecting.c nxglib_nullrect.c nxglib_rectadd.c
 CSRCS += nxglib_rectcopy.c nxglib_rectinside.c nxglib_rectintersect.c
 CSRCS += nxglib_rectoffset.c nxglib_rectoverlap.c nxglib_rectsize.c
-CSRCS += nxglib_rectunion.c nxglib_rgb2yuv.c nxglib_runcopy.c
+CSRCS += nxglib_rectunion.c nxglib_rgb2yuv.c nxglib_rgbblend.c
-CSRCS += nxglib_runoffset.c nxglib_splitline.c nxglib_trapcopy.c
+CSRCS += nxglib_runcopy.c nxglib_runoffset.c nxglib_splitline.c
-CSRCS += nxglib_trapoffset.c nxglib_vectoradd.c nxglib_vectsubtract.c
+CSRCS += nxglib_trapcopy.c nxglib_trapoffset.c nxglib_vectoradd.c
-CSRCS += nxglib_yuv2rgb.c
+CSRCS += nxglib_vectsubtract.c nxglib_yuv2rgb.c
 
 ifneq ($(CONFIG_NX_NPLANES),1)
 CSRCS += nxglib_colorcmp.c nxglib_colorcopy.c