#### resample.c6.1 KB History Raw

 123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138139140141142143144145146147148149150151152153154155156157158159160161162163164165166167168169170171172173174175176177178179180181182183184185186187188189190191192193194195196197198199200201202203204205206207208209210211212213214215216217218219220221222223224225226227228229230231232233234235236237238239240241242243244245246247248249250251252253254255256257258259260261262263264265266267268269270271272273274275276277278279280281282283284285286287288289290291292293294295296297298299300301302303304305306307308309310311312313314315316317318319320321322323324325326327 ``````#include #include #include #include #define K2 7 /* from -.7 to +.7 inclusive, meaning .2 into each adjacent pixel */ #define NK (2*K2+1) double K[NK]; double fac(int L) { int i, f; f = 1; for(i=L; i>1; --i) f *= i; return f; } /* * i0(x) is the modified Bessel function, Σ (x/2)^2L / (L!)² * There are faster ways to calculate this, but we precompute * into a table so let's keep it simple. */ double i0(double x) { double v; int L; v = 1.0; for(L=1; L<10; L++) v += pow(x/2., 2*L)/pow(fac(L), 2); return v; } double kaiser(double x, double τ, double α) { if(fabs(x) > τ) return 0.; return i0(α*sqrt(1-(x*x/(τ*τ))))/i0(α); } void usage(void) { fprint(2, "usage: resample [-x xsize] [-y ysize] [imagefile]\n"); fprint(2, "\twhere size is an integer or a percentage in the form 25%%\n"); exits("usage"); } int getint(char *s, int *percent) { if(s == nil) usage(); *percent = (s[strlen(s)-1] == '%'); if(*s == '+') return atoi(s+1); if(*s == '-') return -atoi(s+1); return atoi(s); } void resamplex(uchar *in, int off, int d, int inx, uchar *out, int outx) { int i, x, k; double X, xx, v, rat; rat = (double)inx/(double)outx; for(x=0; x= inx) i = inx-1; v += in[off+i*d] * K[K2+k]; } out[off+x*d] = v; } } void resampley(uchar **in, int off, int iny, uchar **out, int outy) { int y, i, k; double Y, yy, v, rat; rat = (double)iny/(double)outy; for(y=0; y= iny) i = iny-1; v += in[i][off] * K[K2+k]; } out[y][off] = v; } } int max(int a, int b) { if(a > b) return a; return b; } Memimage* resample(int xsize, int ysize, Memimage *m) { int i, j, bpl, nchan; Memimage *new; uchar **oscan, **nscan; new = allocmemimage(Rect(0, 0, xsize, ysize), m->chan); if(new == nil) sysfatal("can't allocate new image: %r"); oscan = malloc(Dy(m->r)*sizeof(uchar*)); nscan = malloc(max(ysize, Dy(m->r))*sizeof(uchar*)); if(oscan == nil || nscan == nil) sysfatal("can't allocate: %r"); /* unload original image into scan lines */ bpl = bytesperline(m->r, m->depth); for(i=0; ir); i++){ oscan[i] = malloc(bpl); if(oscan[i] == nil) sysfatal("can't allocate: %r"); j = unloadmemimage(m, Rect(m->r.min.x, m->r.min.y+i, m->r.max.x, m->r.min.y+i+1), oscan[i], bpl); if(j != bpl) sysfatal("unloadmemimage"); } /* allocate scan lines for destination. we do y first, so need at least Dy(m->r) lines */ bpl = bytesperline(Rect(0, 0, xsize, Dy(m->r)), m->depth); for(i=0; ir)); i++){ nscan[i] = malloc(bpl); if(nscan[i] == nil) sysfatal("can't allocate: %r"); } /* resample in X */ nchan = m->depth/8; for(i=0; ir); i++){ for(j=0; jchan==XRGB32) continue; resamplex(oscan[i], j, nchan, Dx(m->r), nscan[i], xsize); } free(oscan[i]); oscan[i] = nscan[i]; nscan[i] = malloc(bpl); if(nscan[i] == nil) sysfatal("can't allocate: %r"); } /* resample in Y */ for(i=0; ir), nscan, ysize); /* pack data into destination */ bpl = bytesperline(new->r, m->depth); for(i=0; i 1) usage(); else if(argc == 1){ file = argv[0]; fd = open(file, OREAD); if(fd < 0) sysfatal("can't open %s: %r", file); } m = readmemimage(fd); if(m == nil) sysfatal("can't read %s: %r", file); if(xpercent) xsize = Dx(m->r)*xsize/100; if(ypercent) ysize = Dy(m->r)*ysize/100; if(ysize == 0) ysize = (xsize * Dy(m->r)) / Dx(m->r); if(xsize == 0) xsize = (ysize * Dx(m->r)) / Dy(m->r); new = nil; switch(m->chan){ case GREY8: case RGB24: case RGBA32: case ARGB32: case XRGB32: new = resample(xsize, ysize, m); break; case CMAP8: case RGB15: case RGB16: tchan = RGB24; goto Convert; case GREY1: case GREY2: case GREY4: tchan = GREY8; Convert: /* use library to convert to byte-per-chan form, then convert back */ t1 = allocmemimage(m->r, tchan); if(t1 == nil) sysfatal("can't allocate temporary image: %r"); memimagedraw(t1, t1->r, m, m->r.min, nil, ZP, S); t2 = resample(xsize, ysize, t1); freememimage(t1); new = allocmemimage(Rect(0, 0, xsize, ysize), m->chan); if(new == nil) sysfatal("can't allocate new image: %r"); /* should do error diffusion here */ memimagedraw(new, new->r, t2, t2->r.min, nil, ZP, S); freememimage(t2); break; default: sysfatal("can't handle channel type %s", chantostr(tmp, m->chan)); } assert(new); if(writememimage(1, new) < 0) sysfatal("write error on output: %r"); exits(nil); } ``````