diff options
Diffstat (limited to 'libass/ass_parse.c')
| -rw-r--r-- | libass/ass_parse.c | 29 |
1 files changed, 25 insertions, 4 deletions
diff --git a/libass/ass_parse.c b/libass/ass_parse.c index 5c0ea40..935dbb0 100644 --- a/libass/ass_parse.c +++ b/libass/ass_parse.c @@ -128,21 +128,42 @@ void update_font(ASS_Renderer *render_priv) render_priv->state.font = ass_font_new(render_priv, &desc); } +static double calc_anim(double new, double old, double pwr) +{ + return (1 - pwr) * old + new * pwr; +} + +static int32_t calc_anim_int32(uint32_t new, uint32_t old, double pwr) +{ + double ret = calc_anim(new, old, pwr); + + // Avoid UB on out-of-range values; match x86 behavior + if (isnan(ret) || ret < INT32_MIN || ret > INT32_MAX) + return INT32_MIN; + + return ret; +} + /** * \brief Calculate a weighted average of two colors * calculates c1*(1-a) + c2*a, but separately for each component except alpha */ static void change_color(uint32_t *var, uint32_t new, double pwr) { - (*var) = ((uint32_t) (_r(*var) * (1 - pwr) + _r(new) * pwr) << 24) | - ((uint32_t) (_g(*var) * (1 - pwr) + _g(new) * pwr) << 16) | - ((uint32_t) (_b(*var) * (1 - pwr) + _b(new) * pwr) << 8) | _a(*var); + uint32_t co = ass_bswap32(*var); + uint32_t cn = ass_bswap32(new); + + uint32_t cc = (calc_anim_int32(cn & 0xff0000, co & 0xff0000, pwr) & 0xff0000) | + (calc_anim_int32(cn & 0x00ff00, co & 0x00ff00, pwr) & 0x00ff00) | + (calc_anim_int32(cn & 0x0000ff, co & 0x0000ff, pwr) & 0x0000ff); + + (*var) = (ass_bswap32(cc & 0xffffff)) | _a(*var); } // like change_color, but for alpha component only inline void change_alpha(uint32_t *var, int32_t new, double pwr) { - *var = (*var & 0xFFFFFF00) | (uint8_t) (_a(*var) * (1 - pwr) + new * pwr); + *var = (*var & 0xFFFFFF00) | (uint8_t)calc_anim_int32(_a(new), _a(*var), pwr); } /** |