From: Niklas Haas <g...@haasn.dev>
The current logic uses 12-bit linear light math, which is woefully insufficient
and leads to nasty postarization artifacts. This patch simply switches the
internal logic to 16-bit precision.
This raises the memory requirement of these tables from 32 kB to 272 kB.
Fixes: ticket 4829
Signed-off-by: Niklas Haas <g...@haasn.dev>
Sponsored-by: Sovereign Tech Fund
---
libswscale/swscale.c | 16 ++++++++--------
libswscale/swscale_internal.h | 8 ++++----
libswscale/utils.c | 19 ++++++++++++-------
3 files changed, 24 insertions(+), 19 deletions(-)
diff --git a/libswscale/swscale.c b/libswscale/swscale.c
index 96634acfd6..da3a082905 100644
--- a/libswscale/swscale.c
+++ b/libswscale/swscale.c
@@ -773,10 +773,10 @@ void ff_xyz12Torgb48(const SwsInternal *c, uint8_t *dst,
int dst_stride,
c->xyz2rgb_matrix[2][1] * y +
c->xyz2rgb_matrix[2][2] * z >> 12;
- // limit values to 12-bit depth
- r = av_clip_uintp2(r, 12);
- g = av_clip_uintp2(g, 12);
- b = av_clip_uintp2(b, 12);
+ // limit values to 16-bit depth
+ r = av_clip_uint16(r);
+ g = av_clip_uint16(g);
+ b = av_clip_uint16(b);
// convert from sRGBlinear to RGB and scale from 12bit to 16bit
if (desc->flags & AV_PIX_FMT_FLAG_BE) {
@@ -832,10 +832,10 @@ void ff_rgb48Toxyz12(const SwsInternal *c, uint8_t *dst,
int dst_stride,
c->rgb2xyz_matrix[2][1] * g +
c->rgb2xyz_matrix[2][2] * b >> 12;
- // limit values to 12-bit depth
- x = av_clip_uintp2(x, 12);
- y = av_clip_uintp2(y, 12);
- z = av_clip_uintp2(z, 12);
+ // limit values to 16-bit depth
+ x = av_clip_uint16(x);
+ y = av_clip_uint16(y);
+ z = av_clip_uint16(z);
// convert from XYZlinear to X'Y'Z' and scale from 12bit to 16bit
if (desc->flags & AV_PIX_FMT_FLAG_BE) {
diff --git a/libswscale/swscale_internal.h b/libswscale/swscale_internal.h
index 768e394560..5acd277b50 100644
--- a/libswscale/swscale_internal.h
+++ b/libswscale/swscale_internal.h
@@ -547,10 +547,10 @@ struct SwsInternal {
/* pre defined color-spaces gamma */
#define XYZ_GAMMA (2.6f)
#define RGB_GAMMA (2.2f)
- int16_t *xyzgamma;
- int16_t *rgbgamma;
- int16_t *xyzgammainv;
- int16_t *rgbgammainv;
+ uint16_t *xyzgamma;
+ uint16_t *rgbgamma;
+ uint16_t *xyzgammainv;
+ uint16_t *rgbgammainv;
int16_t xyz2rgb_matrix[3][4];
int16_t rgb2xyz_matrix[3][4];
diff --git a/libswscale/utils.c b/libswscale/utils.c
index 4dedbfc394..937e19f651 100644
--- a/libswscale/utils.c
+++ b/libswscale/utils.c
@@ -948,7 +948,8 @@ static void fill_xyztables(SwsInternal *c)
{1689, 1464, 739},
{ 871, 2929, 296},
{ 79, 488, 3891} };
- static int16_t xyzgamma_tab[4096], rgbgamma_tab[4096],
xyzgammainv_tab[4096], rgbgammainv_tab[4096];
+ static uint16_t xyzgamma_tab[4096], rgbgammainv_tab[4096];
+ static uint16_t rgbgamma_tab[65536], xyzgammainv_tab[65536];
memcpy(c->xyz2rgb_matrix, xyz2rgb_matrix, sizeof(c->xyz2rgb_matrix));
memcpy(c->rgb2xyz_matrix, rgb2xyz_matrix, sizeof(c->rgb2xyz_matrix));
@@ -957,15 +958,19 @@ static void fill_xyztables(SwsInternal *c)
c->xyzgammainv = xyzgammainv_tab;
c->rgbgammainv = rgbgammainv_tab;
- if (rgbgamma_tab[4095])
+ if (xyzgamma_tab[4095])
return;
- /* set gamma vectors */
+ /* set input gamma vectors */
for (i = 0; i < 4096; i++) {
- xyzgamma_tab[i] = lrint(pow(i / 4095.0, xyzgamma) * 4095.0);
- rgbgamma_tab[i] = lrint(pow(i / 4095.0, rgbgamma) * 4095.0);
- xyzgammainv_tab[i] = lrint(pow(i / 4095.0, xyzgammainv) * 4095.0);
- rgbgammainv_tab[i] = lrint(pow(i / 4095.0, rgbgammainv) * 4095.0);
+ xyzgamma_tab[i] = lrint(pow(i / 4095.0, xyzgamma) * 65535.0);
+ rgbgammainv_tab[i] = lrint(pow(i / 4095.0, rgbgammainv) * 65535.0);
+ }
+
+ /* set output gamma vectors */
+ for (i = 0; i < 65536; i++) {
+ rgbgamma_tab[i] = lrint(pow(i / 65535.0, rgbgamma) * 4095.0);
+ xyzgammainv_tab[i] = lrint(pow(i / 65535.0, xyzgammainv) * 4095.0);
}
}
--
2.47.0
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