Fix RANDR’s gamma_to_ramp().

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's avatarJames Cloos <cloos@jhcloos.com>
parent e501c34d
......@@ -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);
}
}
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment