To compute a gamma *correction* lookup table, use the specified gamma
value as the divisor in (1.0/gamma). This matches the semantics of
xgamma(1) and the "gamma-value" and "{red,green,blue}-gamma" xorg.conf(5)
options.
For more details, see:
http://www.poynton.com/PDFs/TIDV/Gamma.pdf (Gamma in computer graphics, page 17)
http://cgit.freedesktop.org/xorg/xserver/tree/hw/xfree86/common/xf86cmap.c:ComputeGamma()
Signed-off-by: Andy Ritger <arit...@nvidia.com>
Reviewed-by: Aaron Plattner <aplatt...@nvidia.com>
---
xrandr.c | 27 +++++++++++++++++++--------
1 files changed, 19 insertions(+), 8 deletions(-)
diff --git a/xrandr.c b/xrandr.c
index 6683ceb..75ed2ee 100644
--- a/xrandr.c
+++ b/xrandr.c
@@ -1326,6 +1326,9 @@ set_gamma(void)
int i, size;
crtc_t *crtc;
XRRCrtcGamma *gamma;
+ float gammaRed;
+ float gammaGreen;
+ float gammaBlue;
if (!(output->changes & changes_gamma))
continue;
@@ -1350,29 +1353,37 @@ set_gamma(void)
continue;
}
- if(output->gamma.red == 0.0 && output->gamma.green == 0.0 &&
output->gamma.blue == 0.0)
- output->gamma.red = output->gamma.green = output->gamma.blue = 1.0;
+ if (output->gamma.red == 0.0)
+ output->gamma.red = 1.0;
+ if (output->gamma.green == 0.0)
+ output->gamma.green = 1.0;
+ if (output->gamma.blue == 0.0)
+ output->gamma.blue = 1.0;
+
+ gammaRed = 1.0 / output->gamma.red;
+ gammaGreen = 1.0 / output->gamma.green;
+ gammaBlue = 1.0 / output->gamma.blue;
for (i = 0; i < size; i++) {
- if (output->gamma.red == 1.0 && output->brightness == 1.0)
+ if (gammaRed == 1.0 && output->brightness == 1.0)
gamma->red[i] = (i << 8) + i;
else
gamma->red[i] = dmin(pow((double)i/(double)(size - 1),
- output->gamma.red) *
output->brightness,
+ gammaRed) * output->brightness,
1.0) * 65535.0;
- if (output->gamma.green == 1.0 && output->brightness == 1.0)
+ if (gammaGreen == 1.0 && output->brightness == 1.0)
gamma->green[i] = (i << 8) + i;
else
gamma->green[i] = dmin(pow((double)i/(double)(size - 1),
- output->gamma.green) *
output->brightness,
+ gammaGreen) * output->brightness,
1.0) * 65535.0;
- if (output->gamma.blue == 1.0 && output->brightness == 1.0)
+ if (gammaBlue == 1.0 && output->brightness == 1.0)
gamma->blue[i] = (i << 8) + i;
else
gamma->blue[i] = dmin(pow((double)i/(double)(size - 1),
- output->gamma.blue) *
output->brightness,
+ gammaBlue) * output->brightness,
1.0) * 65535.0;
}
--
1.7.2.5
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