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#ifndef lint
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static const char RCSid[] = "$Id: ccyrgb.c,v 3.4 2012/05/17 17:11:33 greg Exp $";
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#endif
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/*
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* Convert MGF color to Radiance RGB and spectral representations
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*/
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#include <stdio.h>
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#include "color.h"
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#include "ccolor.h"
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void
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ccy2rgb( /* convert MGF color to RGB */
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C_COLOR *cin, /* input MGF chrominance */
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double cieY, /* input luminance or reflectance */
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COLOR cout /* output RGB color */
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)
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{
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double d;
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COLOR xyz;
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/* get CIE XYZ representation */
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c_ccvt(cin, C_CSXY);
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d = cin->cx/cin->cy;
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xyz[CIEX] = d * cieY;
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xyz[CIEY] = cieY;
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xyz[CIEZ] = (1./cin->cy - d - 1.) * cieY;
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cie_rgb(cout, xyz);
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}
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/* Convert RGB to MGF color and value */
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double
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rgb2ccy(COLOR cin, C_COLOR *cout)
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{
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COLOR xyz;
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double df;
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rgb_cie(xyz, cin);
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*cout = c_dfcolor;
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df = xyz[CIEX] + xyz[CIEY] + xyz[CIEZ];
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if (df <= .0)
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return(.0);
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df = 1./df;
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cout->cx = xyz[CIEX]*df;
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cout->cy = xyz[CIEZ]*df;
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cout->flags = (C_CSXY|C_CDXY);
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return(xyz[CIEY]);
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}
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void
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ccy2scolor( /* convert MGF color, Y to spectral color */
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C_COLOR *cin, /* input MGF color or spectrum */
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double cieY, /* input luminance or reflectance */
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SCOLOR sco /* output spectral color */
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)
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{
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COLORV nf, sorig[C_CNSS];
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int i;
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if (cin->flags & C_CDXY || NCSAMP <= 3) {
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COLOR col; /* tristimulus in or out, so... */
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ccy2rgb(cin, cieY, col);
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setscolor(sco, colval(col,RED), colval(col,GRN), colval(col,BLU));
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return;
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}
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c_ccvt(cin, C_CSXY);
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nf = cieY*C_CNSS/(cin->ssum*3*cin->cy);
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for (i = C_CNSS; i--; ) /* may as well reverse order */
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sorig[C_CNSS-1-i] = nf*(COLORV)cin->ssamp[i];
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convertscolor(sco, NCSAMP, WLPART[0], WLPART[3],
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sorig, C_CNSS, C_CMAXWL+.5*C_CWLI, C_CMINWL-.5*C_CWLI);
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}
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/* Convert spectral color to MGF color and Y value */
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double
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scolor2ccy(SCOLOR sci, C_COLOR *cout)
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{
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float hinc, cspec[MAXCSAMP];
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int i = NCSAMP;
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if (i <= 3) /* defined as RGB, so... */
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return(rgb2ccy(sci, cout));
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while (i-- > 0) /* need to reverse array */
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cspec[i] = sci[NCSAMP-1-i];
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hinc = (WLPART[0]-WLPART[3])/(float)(2*NCSAMP);
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return(c_sset(cout, WLPART[3]+hinc, WLPART[0]-hinc, cspec, NCSAMP));
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}
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