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#ifndef lint
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static const char RCSid[] = "$Id: pf2.c,v 2.10 2023/12/07 21:15:54 greg Exp $";
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#endif
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/*
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* pf2.c - routines used by pfilt.
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*/
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#include "pfilt.h"
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#include "random.h"
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#define AVGLVL 0.5 /* target mean brightness */
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double avgbrt; /* average picture brightness */
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long npix; /* # pixels in average */
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typedef struct hotpix { /* structure for avgbrt pixels */
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struct hotpix *next; /* next in list */
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COLOR val; /* pixel color */
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short x, y; /* pixel position */
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float slope; /* random slope for diffraction */
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} HOTPIX;
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HOTPIX *head; /* head of avgbrt pixel list */
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double sprdfact; /* computed spread factor */
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static void starpoint(SCOLOR fcol, int x, int y, HOTPIX *hp);
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void
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pass1init(void) /* prepare for first pass */
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{
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avgbrt = 0.0;
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npix = 0;
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head = NULL;
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}
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void
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pass1default(void) /* for single pass */
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{
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avgbrt = AVGLVL;
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npix = 1;
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head = NULL;
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}
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void
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pass1scan( /* process first pass scanline */
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COLORV *scan,
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int y
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)
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{
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double cbrt;
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int x;
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HOTPIX *hp;
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for (x = 0; x < xres; x++) {
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cbrt = (*ourbright)(scan+x*NCSAMP);
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if (cbrt <= 0)
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continue;
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if (avghot || cbrt < hotlvl) {
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avgbrt += cbrt;
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npix++;
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}
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if (npts && cbrt >= hotlvl) {
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hp = (HOTPIX *)malloc(sizeof(HOTPIX));
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if (hp == NULL) {
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fprintf(stderr, "%s: out of memory\n",
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progname);
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quit(1);
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}
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scolor_color(hp->val, scan+x*NCSAMP);
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hp->x = x;
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hp->y = y;
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hp->slope = ttan(PI*(0.5-(irandom(npts)+0.5)/npts));
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hp->next = head;
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head = hp;
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}
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}
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}
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void
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pass2init(void) /* prepare for final pass */
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{
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if (!npix) {
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fprintf(stderr, "%s: picture too dark or too bright\n",
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progname);
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quit(1);
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}
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avgbrt /= (double)npix;
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scalecolor(exposure, AVGLVL/avgbrt);
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sprdfact = spread / (hotlvl * bright(exposure))
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* ((double)xres*xres + (double)yres*yres) / 4.0;
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}
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void
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pass2scan( /* process final pass scanline */
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COLORV *scan,
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int y
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)
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{
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int xmin, xmax;
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int x;
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HOTPIX *hp;
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for (hp = head; hp != NULL; hp = hp->next) {
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if (hp->slope > FTINY) {
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xmin = (y - hp->y - 0.5)/hp->slope + hp->x;
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xmax = (y - hp->y + 0.5)/hp->slope + hp->x;
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} else if (hp->slope < -FTINY) {
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xmin = (y - hp->y + 0.5)/hp->slope + hp->x;
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xmax = (y - hp->y - 0.5)/hp->slope + hp->x;
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} else if (y == hp->y) {
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xmin = 0;
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xmax = xres-1;
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} else {
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xmin = 1;
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xmax = 0;
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}
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if (xmin < 0)
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xmin = 0;
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if (xmax >= xres)
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xmax = xres-1;
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for (x = xmin; x <= xmax; x++)
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starpoint(scan+x*NCSAMP, x, y, hp);
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}
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for (x = 0; x < xres; x++)
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smultcolor(scan+x*NCSAMP, exposure);
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}
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static void
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starpoint( /* pixel is on the star's point */
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SCOLOR fcol,
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int x,
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int y,
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HOTPIX *hp
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)
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{
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COLOR ctmp;
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double d2;
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d2 = (double)(x - hp->x)*(x - hp->x) + (double)(y - hp->y)*(y - hp->y);
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if (d2 > sprdfact) {
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d2 = sprdfact / d2;
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if (d2 < FTINY)
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return;
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copycolor(ctmp, hp->val);
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scalecolor(ctmp, d2);
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saddcolor(fcol, ctmp);
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} else if (d2 > FTINY) {
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saddcolor(fcol, hp->val);
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}
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}
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