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RadiancePmap/rgbecontrib.c
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rgbecontrib.c
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/*
=========================================================================
Routines to encode/decode RGBE representation of normalised binned
contributions. See rgbecontrib.h for encoding details.
Compile with -D_RGBE_CONTRIB_TEST to enable unit test.
Roland Schregle (roland.schregle@{hslu.ch, gmail.com})
(c) Lucerne University of Applied Sciences and Arts,
supported by the Swiss National Science Foundation
(SNSF #179067, "Light Fields for Spatio-Temporal Glare Assessment")
=========================================================================
$Id$
*/
#include "rgbecontrib.h"
#include <stdlib.h>
#include <stdio.h>
#include <math.h>
#define absMax(a, b) (fabs(a) > fabs(b) ? a : b)
#define sgn(a) ((a) >= 0 ? 1 : -1)
RGBEContrib RGBEContribEnc (double rgb [3], unsigned bin)
/* Encode signed float RGB contributions with associated bin to RGBE. */
{
double rgbMax = absMax(absMax(rgb [0], rgb [1]), rgb [2]), mant;
int exp2;
RGBEContrib rgbeCont = {0, 0, 0, 0};
/* Check and set bin */
if (bin > RGBE_CONTRIB_MAXBIN) {
fprintf(stderr, "WARNING - RGBEContrib bin overflow\n");
return rgbeCont;
}
else
rgbeCont.bin = bin;
/* Check RGB range */
if (fabs(rgbMax) < RGBE_CONTRIB_MIN) {
/* Below encoding range, clamp to zero */
fprintf(stderr, "WARNING - RGBEContrib underflow, clamping to 0\n");
return rgbeCont;
}
if (fabs(rgbMax) > RGBE_CONTRIB_MAX) {
/* Exceeds encoding range, clamp to maximum */
fprintf(
stderr,
"WARNING - RGBEContrib overflow, clamping to %d\n", sgn(rgbMax)
);
rgbeCont.red = rgbeCont.grn = rgbeCont.blu =
sgn(rgbMax) * ((1 << RGBE_CONTRIB_MAXMANT) - 1);
return rgbeCont;
}
/* Get max mantissa and normalise, get exponent to base 2 */
mant = frexp(rgbMax, &exp2) * RGBE_CONTRIB_MAXMANT / rgbMax;
/* Set RGB integer mantissas, rounding up or down depending on sign, and
* add zero offset */
rgbeCont.red = (int)(
rgb [0] * mant + 0.5 * sgn(rgb [0]) + RGBE_CONTRIB_MAXMANT
);
rgbeCont.grn = (int)(
rgb [1] * mant + 0.5 * sgn(rgb [1]) + RGBE_CONTRIB_MAXMANT
);
rgbeCont.blu = (int)(
rgb [2] * mant + 0.5 * sgn(rgb [2]) + RGBE_CONTRIB_MAXMANT
);
/* Drop the exponent sign, since implicitly negative */
rgbeCont.exp = abs(exp2);
return rgbeCont;
}
unsigned RGBEContribDec (RGBEContrib rgbeCont, double rgb [3])
/* Decode rgbeCont, returning signed floating point contributions in array
* rgb, and the associated bin as return value */
{
}
#ifdef _RGBE_CONTRIB_TEST
/* Build standalone to run unit test */
int main ()
{
double rgb [3] = {0, 0, 0};
/* Test range checks */
RGBEContribEnc(rgb, RGBE_CONTRIB_MAXBIN << 1);
rgb [0] = RGBE_CONTRIB_MIN / 2;
RGBEContribEnc(rgb, 0);
rgb [0] = 2;
RGBEContribEnc(rgb, 0);
rgb [0] = -2;
RGBEContribEnc(rgb, 0);
return 0;
}
#endif
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