From: Jeff Muizelaar <jmuizelaar@mozilla.com>
Date: Thu, 17 Jul 2008 17:32:08 +0000 (-0400)
Subject: Comment FbByteMulAdd
X-Git-Tag: 1.0_branch~1288
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=d4855cd9d028c49c2a12f61c6227579fcb8af5b6;p=profile%2Fivi%2Fpixman.git

Comment FbByteMulAdd
---

diff --git a/pixman/combine.h.inc b/pixman/combine.h.inc
index 7dd97ae..8c70cb7 100644
--- a/pixman/combine.h.inc
+++ b/pixman/combine.h.inc
@@ -57,19 +57,31 @@
   x_c = (x_c * a) / 255 + y
 */
 #define FbByteMulAdd(x, a, y) do {                                      \
+        /* multiply and divide: trunc((i + 128)*257/65536) */           \
         comp4_t t = ((x & RB_MASK) * a) + RB_ONE_HALF;                  \
         t = (t + ((t >> COMPONENT_SIZE) & RB_MASK)) >> COMPONENT_SIZE;  \
         t &= RB_MASK;                                                   \
+                                                                        \
+        /* add */                                                       \
         t += y & RB_MASK;                                               \
+                                                                        \
+        /* saturate */                                                  \
         t |= RB_MASK_PLUS_ONE - ((t >> COMPONENT_SIZE) & RB_MASK);      \
         t &= RB_MASK;                                                   \
                                                                         \
+        /* multiply and divide */                                       \
         x = (((x >> COMPONENT_SIZE) & RB_MASK) * a) + RB_ONE_HALF;      \
         x = (x + ((x >> COMPONENT_SIZE) & RB_MASK)) >> COMPONENT_SIZE;  \
         x &= RB_MASK;                                                   \
+                                                                        \
+        /* add */                                                       \
         x += (y >> COMPONENT_SIZE) & RB_MASK;                           \
+                                                                        \
+        /* saturate */                                                  \
         x |= RB_MASK_PLUS_ONE - ((x >> COMPONENT_SIZE) & RB_MASK);      \
         x &= RB_MASK;                                                   \
+                                                                        \
+        /* recombine */                                                 \
         x <<= COMPONENT_SIZE;                                           \
         x += t;                                                         \
     } while (0)