diff options
Diffstat (limited to 'libass/ass_bitmap.c')
| -rw-r--r-- | libass/ass_bitmap.c | 29 |
1 files changed, 29 insertions, 0 deletions
diff --git a/libass/ass_bitmap.c b/libass/ass_bitmap.c index 5f0991d..286f904 100644 --- a/libass/ass_bitmap.c +++ b/libass/ass_bitmap.c @@ -749,6 +749,35 @@ void be_blur_post(uint8_t *buf, intptr_t w, intptr_t h, intptr_t stride) } } +/* + * To find these values, simulate blur on the border between two + * half-planes, one zero-filled (background) and the other filled + * with the maximum supported value (foreground). Keep incrementing + * the \be argument. The necessary padding is the distance by which + * the blurred foreground image extends beyond the original border + * and into the background. Initially it increases along with \be, + * but very soon it grinds to a halt. At some point, the blurred + * image actually reaches a stationary point and stays unchanged + * forever after, simply _shifting_ by one pixel for each \be + * step--moving in the direction of the non-zero half-plane and + * thus decreasing the necessary padding (although the large + * padding is still needed for intermediate results). In practice, + * images are finite rather than infinite like half-planes, but + * this can only decrease the required padding. Half-planes filled + * with extreme values are the theoretical limit of the worst case. + * Make sure to use the right pixel value range in the simulation! + */ +int be_padding(int be) +{ + if (be <= 3) + return be; + if (be <= 7) + return 4; + if (be <= 123) + return 5; + return FFMAX(128 - be, 0); +} + int outline_to_bitmap2(ASS_Renderer *render_priv, ASS_Outline *outline, ASS_Outline *border, Bitmap **bm_g, Bitmap **bm_o) |