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wrlib: changed Gamma Correction calculation to use single-precision float

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The original code was using double precision floating point to perform the
color corrections for the creation of the standard colormap. This precision
is not necessary because color coding is 16 bits anyway, and on some
architecture the double precision comes with a cost.

Signed-off-by: Christophe CURIS <christophe.curis@free.fr>
This commit is contained in:
Christophe CURIS
2015-05-24 15:49:09 +02:00
committed by Carlos R. Mafra
parent 9ab2203456
commit b64d9e6be0
2 changed files with 16 additions and 11 deletions
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1
m4/wm_libmath.m4
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@@ -70,6 +70,7 @@ AC_CACHE_CHECK([if sinf+cosf are defined in math.h], [wm_cv_libm_sinf],
a = atan2f(a, b);
b = cosf(a);
a = sinf(b);
a = powf(a, b);
return (int)a;])],
[wm_cv_libm_sinf="`echo "$wm_arg" | sed -e 's,^.*% *,,' `" ; break])
done

26
wrlib/context.c
View File

@@ -38,6 +38,10 @@
#include "scale.h"
#ifndef HAVE_FLOAT_MATHFUNC
#define powf(x, y) ((float) pow((double)(x), (double)(y)))
#endif
static Bool bestContext(Display * dpy, int screen_number, RContext * context);
static const RContextAttributes DEFAULT_CONTEXT_ATTRIBS = {
@@ -248,13 +252,13 @@ static Bool allocatePseudoColor(RContext *ctx)
if ((ctx->attribs->flags & RC_GammaCorrection) && ctx->attribs->rgamma > 0
&& ctx->attribs->ggamma > 0 && ctx->attribs->bgamma > 0) {
double rg, gg, bg;
double tmp;
float rg, gg, bg;
float tmp;
/* do gamma correction */
rg = 1.0 / ctx->attribs->rgamma;
gg = 1.0 / ctx->attribs->ggamma;
bg = 1.0 / ctx->attribs->bgamma;
rg = 1.0F / ctx->attribs->rgamma;
gg = 1.0F / ctx->attribs->ggamma;
bg = 1.0F / ctx->attribs->bgamma;
for (r = 0; r < cpc; r++) {
for (g = 0; g < cpc; g++) {
for (b = 0; b < cpc; b++) {
@@ -263,14 +267,14 @@ static Bool allocatePseudoColor(RContext *ctx)
colors[i].blue = (b * 0xffff) / (cpc - 1);
colors[i].flags = DoRed | DoGreen | DoBlue;
tmp = (double)colors[i].red / 65536.0;
colors[i].red = (unsigned short)(65536.0 * pow(tmp, rg));
tmp = (float) colors[i].red / 65536.0F;
colors[i].red = (unsigned short)(65536.0F * powf(tmp, rg));
tmp = (double)colors[i].green / 65536.0;
colors[i].green = (unsigned short)(65536.0 * pow(tmp, gg));
tmp = (float) colors[i].green / 65536.0F;
colors[i].green = (unsigned short)(65536.0F * powf(tmp, gg));
tmp = (double)colors[i].blue / 65536.0;
colors[i].blue = (unsigned short)(65536.0 * pow(tmp, bg));
tmp = (float) colors[i].blue / 65536.0F;
colors[i].blue = (unsigned short)(65536.0F * powf(tmp, bg));
i++;
}