Calculate \be using [0..64] value range (like VSFilter)

To avoid banding in the output, the full [0..255] value range
is restored before the last \be pass, which then uses the full
range and hides the bands by virtue of being a blur.

With this, our \be finally closely matches VSFilter's.

The only visible difference (other than the lack of banding) is
in clipping: we add proper padding and output the whole blurred
image, while VSFilter does not add any padding and hence clips
the blurred image too early.

1 files changed, 4 insertions, 0 deletions

diff --git a/libass/ass_bitmap.h b/libass/ass_bitmap.h
index 9a36a3ec..5014f51a 100644
--- a/libass/ass_bitmap.h
+++ b/libass/ass_bitmap.h
@@ -72,6 +72,10 @@ void ass_gauss_blur(unsigned char *buffer, unsigned *tmp2,
 void be_blur_c(uint8_t *buf, intptr_t w,
                intptr_t h, intptr_t stride,
                uint16_t *tmp);
+void be_blur_pre(uint8_t *buf, intptr_t w,
+                 intptr_t h, intptr_t stride);
+void be_blur_post(uint8_t *buf, intptr_t w,
+                  intptr_t h, intptr_t stride);
 void add_bitmaps_c(uint8_t *dst, intptr_t dst_stride,
                    uint8_t *src, intptr_t src_stride,
                    intptr_t height, intptr_t width);