In order to generate a 256-entry ramp in [0,65535] which covers the full
range, one must mupliply eight-bit values not by 256 but rather by 257.
Many years back – well before the RANDR extension was written, and
before xorg@fdo – a similar bug fix was made to the DIX for converting
client-supplied eight-bit color values into sixteen-bit values.
Noticed by: Elle Stone and Graeme Gill.
Signed-off-by: James Cloos <[email protected]>
---
hw/xfree86/modes/xf86RandR12.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/hw/xfree86/modes/xf86RandR12.c b/hw/xfree86/modes/xf86RandR12.c
index a773c34..aca0734 100644
--- a/hw/xfree86/modes/xf86RandR12.c
+++ b/hw/xfree86/modes/xf86RandR12.c
@@ -1679,11 +1679,11 @@ gamma_to_ramp(float gamma, CARD16 *ramp, int size)
for (i = 0; i < size; i++) {
if (gamma == 1.0)
- ramp[i] = i << 8;
+ ramp[i] = i | i << 8;
else
ramp[i] =
(CARD16) (pow((double) i / (double) (size - 1), 1. / gamma)
- * (double) (size - 1) * 256);
+ * (double) (size - 1) * 257);
}
}
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