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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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|
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#include "pfilt.h" |
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#include "random.h" |
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|
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#define AVGLVL 0.5 /* target mean brightness */ |
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|
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double avgbrt; /* average picture brightness */ |
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long npix; /* # pixels in average */ |
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|
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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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|
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HOTPIX *head; /* head of avgbrt pixel list */ |
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|
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double sprdfact; /* computed spread factor */ |
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|
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static void starpoint(SCOLOR fcol, int x, int y, HOTPIX *hp); |
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|
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|
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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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|
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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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|
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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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|
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for (x = 0; x < xres; x++) { |
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|
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cbrt = (*ourbright)(scan+x*NCSAMP); |
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|
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if (cbrt <= 0) |
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continue; |
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|
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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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|
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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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|
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scalecolor(exposure, AVGLVL/avgbrt); |
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|
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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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|
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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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|
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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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|
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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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|
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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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} |
