vf_overlay: adopts FAST_DIV255 macro for calculating destination alpha

Ease readability, improve exactness.
14 years ago · 0b3e9d5dc6
parent 91dfb73852
commit 0b3e9d5dc6
1 changed files with 2 additions and 1 deletions
--- a/libavfilter/vf_overlay.c
+++ b/libavfilter/vf_overlay.c
@ -452,7 +452,8 @@ static void blend_slice(AVFilterContext *ctx,
                        alpha = (alpha_v + alpha_h) >> 1;
                    } else
                        alpha = a[0];
-                    *d = (*d * (0xff - alpha) + *s++ * alpha + 128) >> 8;
+                    *d = FAST_DIV255(*d * (255 - alpha) + *s * alpha);
+                    s++;
                    d++;
                    a += 1 << hsub;
                }