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author | Oleg Oshmyan <chortos@inbox.lv> | 2015-02-09 15:18:44 +0200 |
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committer | Oleg Oshmyan <chortos@inbox.lv> | 2015-02-10 04:42:35 +0200 |
commit | e55955084f66971f6a268e0d0641da1f132fa979 (patch) | |
tree | 5e77ef1254f329650b2e7b9e4f104bb0a1fcbfab | |
parent | 0f367cc55086e46070e4c4cda9a1800176bed3c0 (diff) | |
download | libass-e55955084f66971f6a268e0d0641da1f132fa979.tar.bz2 libass-e55955084f66971f6a268e0d0641da1f132fa979.tar.xz |
Add enough padding for \be to avoid clipping
To avoid making bitmaps unnecessarily large, use just
the necessary amount of padding for the given \be value.
-rw-r--r-- | libass/ass_bitmap.c | 29 | ||||
-rw-r--r-- | libass/ass_bitmap.h | 1 | ||||
-rw-r--r-- | libass/ass_render.c | 2 |
3 files changed, 31 insertions, 1 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) diff --git a/libass/ass_bitmap.h b/libass/ass_bitmap.h index 5014f51..901adc7 100644 --- a/libass/ass_bitmap.h +++ b/libass/ass_bitmap.h @@ -69,6 +69,7 @@ void ass_free_bitmap(Bitmap *bm); void ass_gauss_blur(unsigned char *buffer, unsigned *tmp2, int width, int height, int stride, unsigned *m2, int r, int mwidth); +int be_padding(int be); void be_blur_c(uint8_t *buf, intptr_t w, intptr_t h, intptr_t stride, uint16_t *tmp); diff --git a/libass/ass_render.c b/libass/ass_render.c index 6140788..a02bcab 100644 --- a/libass/ass_render.c +++ b/libass/ass_render.c @@ -2257,7 +2257,7 @@ static void render_and_combine_glyphs(ASS_Renderer *render_priv, continue; } - int bbord = info->filter.be > 0 ? sqrt(2 * info->filter.be) : 0; + int bbord = be_padding(info->filter.be); int gbord = info->filter.blur > 0.0 ? FFMIN(info->filter.blur + 1, INT_MAX) : 0; int bord = FFMAX(bbord, gbord); |