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* grub-core/video/bitmap_scale.c (scale_bilinear): Increased precision

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to eliminate artefacts in bilinear interpolation.
This commit is contained in:
Vladimir Testov committed 2013-10-01 16:34:04 +04:00
1 parent 2b131610d0
commit d999ac72e2
2 files changed
+17 -10
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grub-core/video/bitmap_scale.c
+12 -10
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@@ -286,18 +286,20 @@ scale_bilinear (struct grub_video_bitmap *dst, struct grub_video_bitmap *src)
{
/* Get the component's values for the
four source corner pixels. */
grub_uint8_t f00 = sptr[comp];
grub_uint8_t f10 = sptr[comp + bytes_per_pixel];
grub_uint8_t f01 = sptr[comp + sstride];
grub_uint8_t f11 = sptr[comp + sstride + bytes_per_pixel];
int f00 = sptr[comp];
int f10 = sptr[comp + bytes_per_pixel];
int f01 = sptr[comp + sstride];
int f11 = sptr[comp + sstride + bytes_per_pixel];
/* Do linear interpolations along the top and bottom
rows of the box. */
grub_uint8_t f0y = (256 - v) * f00 / 256 + v * f01 / 256;
grub_uint8_t f1y = (256 - v) * f10 / 256 + v * f11 / 256;
/* Count coeffecients. */
int c00 = (256 - u) * (256 - v);
int c10 = u * (256 - v);
int c01 = (256 - u) * v;
int c11 = u * v;
/* Interpolate vertically. */
grub_uint8_t fxy = (256 - u) * f0y / 256 + u * f1y / 256;
/* Interpolate. */
int fxy = c00 * f00 + c01 * f01 + c10 * f10 + c11 * f11;
fxy = fxy / (256 * 256);
dptr[comp] = fxy;
}