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327
src/cmd/resample.c
Executable file
327
src/cmd/resample.c
Executable file
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#include <u.h>
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#include <libc.h>
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#include <draw.h>
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#include <memdraw.h>
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#define K2 7 /* from -.7 to +.7 inclusive, meaning .2 into each adjacent pixel */
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#define NK (2*K2+1)
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double K[NK];
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double
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fac(int L)
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{
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int i, f;
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f = 1;
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for(i=L; i>1; --i)
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f *= i;
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return f;
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}
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/*
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* i0(x) is the modified Bessel function, Σ (x/2)^2L / (L!)²
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* There are faster ways to calculate this, but we precompute
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* into a table so let's keep it simple.
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*/
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double
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i0(double x)
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{
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double v;
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int L;
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v = 1.0;
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for(L=1; L<10; L++)
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v += pow(x/2., 2*L)/pow(fac(L), 2);
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return v;
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}
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double
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kaiser(double x, double tau, double alpha)
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{
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if(fabs(x) > tau)
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return 0.;
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return i0(alpha*sqrt(1-(x*x/(tau*tau))))/i0(alpha);
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}
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void
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usage(void)
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{
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fprint(2, "usage: resample [-x xsize] [-y ysize] [imagefile]\n");
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fprint(2, "\twhere size is an integer or a percentage in the form 25%%\n");
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exits("usage");
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}
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int
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getint(char *s, int *percent)
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{
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if(s == nil)
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usage();
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*percent = (s[strlen(s)-1] == '%');
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if(*s == '+')
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return atoi(s+1);
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if(*s == '-')
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return -atoi(s+1);
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return atoi(s);
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}
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void
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resamplex(uchar *in, int off, int d, int inx, uchar *out, int outx)
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{
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int i, x, k;
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double X, xx, v, rat;
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rat = (double)inx/(double)outx;
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for(x=0; x<outx; x++){
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if(inx == outx){
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/* don't resample if size unchanged */
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out[off+x*d] = in[off+x*d];
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continue;
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}
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v = 0.0;
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X = x*rat;
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for(k=-K2; k<=K2; k++){
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xx = X + rat*k/10.;
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i = xx;
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if(i < 0)
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i = 0;
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if(i >= inx)
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i = inx-1;
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v += in[off+i*d] * K[K2+k];
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}
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out[off+x*d] = v;
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}
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}
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void
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resampley(uchar **in, int off, int iny, uchar **out, int outy)
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{
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int y, i, k;
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double Y, yy, v, rat;
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rat = (double)iny/(double)outy;
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for(y=0; y<outy; y++){
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if(iny == outy){
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/* don't resample if size unchanged */
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out[y][off] = in[y][off];
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continue;
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}
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v = 0.0;
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Y = y*rat;
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for(k=-K2; k<=K2; k++){
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yy = Y + rat*k/10.;
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i = yy;
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if(i < 0)
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i = 0;
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if(i >= iny)
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i = iny-1;
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v += in[i][off] * K[K2+k];
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}
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out[y][off] = v;
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}
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}
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int
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max(int a, int b)
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{
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if(a > b)
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return a;
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return b;
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}
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Memimage*
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resample(int xsize, int ysize, Memimage *m)
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{
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int i, j, bpl, nchan;
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Memimage *new;
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uchar **oscan, **nscan;
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new = allocmemimage(Rect(0, 0, xsize, ysize), m->chan);
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if(new == nil)
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sysfatal("can't allocate new image: %r");
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oscan = malloc(Dy(m->r)*sizeof(uchar*));
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nscan = malloc(max(ysize, Dy(m->r))*sizeof(uchar*));
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if(oscan == nil || nscan == nil)
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sysfatal("can't allocate: %r");
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/* unload original image into scan lines */
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bpl = bytesperline(m->r, m->depth);
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for(i=0; i<Dy(m->r); i++){
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oscan[i] = malloc(bpl);
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if(oscan[i] == nil)
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sysfatal("can't allocate: %r");
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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);
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if(j != bpl)
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sysfatal("unloadmemimage");
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}
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/* allocate scan lines for destination. we do y first, so need at least Dy(m->r) lines */
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bpl = bytesperline(Rect(0, 0, xsize, Dy(m->r)), m->depth);
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for(i=0; i<max(ysize, Dy(m->r)); i++){
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nscan[i] = malloc(bpl);
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if(nscan[i] == nil)
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sysfatal("can't allocate: %r");
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}
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/* resample in X */
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nchan = m->depth/8;
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for(i=0; i<Dy(m->r); i++){
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for(j=0; j<nchan; j++){
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if(j==0 && m->chan==XRGB32)
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continue;
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resamplex(oscan[i], j, nchan, Dx(m->r), nscan[i], xsize);
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}
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free(oscan[i]);
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oscan[i] = nscan[i];
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nscan[i] = malloc(bpl);
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if(nscan[i] == nil)
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sysfatal("can't allocate: %r");
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}
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/* resample in Y */
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for(i=0; i<xsize; i++)
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for(j=0; j<nchan; j++)
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resampley(oscan, nchan*i+j, Dy(m->r), nscan, ysize);
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/* pack data into destination */
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bpl = bytesperline(new->r, m->depth);
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for(i=0; i<ysize; i++){
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j = loadmemimage(new, Rect(0, i, xsize, i+1), nscan[i], bpl);
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if(j != bpl)
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sysfatal("loadmemimage: %r");
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}
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return new;
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}
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void
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main(int argc, char *argv[])
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{
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int i, fd, xsize, ysize, xpercent, ypercent;
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Rectangle rparam;
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Memimage *m, *new, *t1, *t2;
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char *file;
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ulong tchan;
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char tmp[100];
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double v;
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for(i=-K2; i<=K2; i++){
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K[K2+i] = kaiser(i/10., K2/10., 4.);
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// print("%g %g\n", i/10., K[K2+i]);
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}
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/* normalize */
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v = 0.0;
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for(i=0; i<NK; i++)
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v += K[i];
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for(i=0; i<NK; i++)
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K[i] /= v;
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memimageinit();
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memset(&rparam, 0, sizeof rparam);
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xsize = ysize = 0;
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xpercent = ypercent = 0;
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ARGBEGIN{
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case 'a': /* compatibility; equivalent to just -x or -y */
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if(xsize != 0 || ysize != 0)
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usage();
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xsize = getint(ARGF(), &xpercent);
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if(xsize <= 0)
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usage();
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ysize = xsize;
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ypercent = xpercent;
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break;
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case 'x':
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if(xsize != 0)
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usage();
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xsize = getint(ARGF(), &xpercent);
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if(xsize <= 0)
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usage();
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break;
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case 'y':
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if(ysize != 0)
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usage();
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ysize = getint(ARGF(), &ypercent);
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if(ysize <= 0)
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usage();
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break;
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default:
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usage();
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}ARGEND
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if(xsize == 0 && ysize == 0)
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usage();
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file = "<stdin>";
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fd = 0;
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if(argc > 1)
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usage();
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else if(argc == 1){
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file = argv[0];
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fd = open(file, OREAD);
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if(fd < 0)
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sysfatal("can't open %s: %r", file);
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}
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m = readmemimage(fd);
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if(m == nil)
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sysfatal("can't read %s: %r", file);
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if(xpercent)
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xsize = Dx(m->r)*xsize/100;
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if(ypercent)
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ysize = Dy(m->r)*ysize/100;
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if(ysize == 0)
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ysize = (xsize * Dy(m->r)) / Dx(m->r);
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if(xsize == 0)
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xsize = (ysize * Dx(m->r)) / Dy(m->r);
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new = nil;
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switch(m->chan){
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case GREY8:
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case RGB24:
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case RGBA32:
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case ARGB32:
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case XRGB32:
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new = resample(xsize, ysize, m);
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break;
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case CMAP8:
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case RGB15:
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case RGB16:
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tchan = RGB24;
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goto Convert;
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case GREY1:
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case GREY2:
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case GREY4:
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tchan = GREY8;
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Convert:
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/* use library to convert to byte-per-chan form, then convert back */
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t1 = allocmemimage(m->r, tchan);
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if(t1 == nil)
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sysfatal("can't allocate temporary image: %r");
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memimagedraw(t1, t1->r, m, m->r.min, nil, ZP, S);
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t2 = resample(xsize, ysize, t1);
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freememimage(t1);
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new = allocmemimage(Rect(0, 0, xsize, ysize), m->chan);
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if(new == nil)
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sysfatal("can't allocate new image: %r");
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/* should do error diffusion here */
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memimagedraw(new, new->r, t2, t2->r.min, nil, ZP, S);
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freememimage(t2);
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break;
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default:
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sysfatal("can't handle channel type %s", chantostr(tmp, m->chan));
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}
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assert(new);
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if(writememimage(1, new) < 0)
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sysfatal("write error on output: %r");
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exits(nil);
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}
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