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TeX 1995 July
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TeX CD-ROM July 1995 (Disc 1)(Walnut Creek)(1995).ISO
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umddvi
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lib
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conv.c
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1990-10-01
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/*
* Copyright (c) 1987 University of Maryland Department of Computer Science.
* All rights reserved. Permission to copy for any purpose is hereby granted
* so long as this copyright notice remains intact.
*/
#ifndef lint
static char rcsid[] = "$Header: conv.c,v 1.3 87/06/16 18:27:39 chris Exp $";
#endif
/*
* Conversions.
*/
#include "types.h"
#include "conv.h"
double DMagFactor();
/*
* Set a conversion (possibly the global conversion).
*/
void
CSetConversion(c, dpi, usermag, num, denom, dvimag)
register struct conversion *c;
int dpi, usermag;
i32 num, denom, dvimag;
{
double ddpi = dpi;
c->c_mag = DMagFactor((int) dvimag) * DMagFactor(usermag);
c->c_dpi = ddpi;
/*
* The conversion facture is figured as follows: there are exactly
* num/denom DVI units per decimicron, and 254000 decimicrons per
* inch, and dpi pixels per inch. Then we have to adjust this by
* the stated magnification.
*/
c->c_fromsp = (num / 254000.0) * (ddpi / denom) * c->c_mag;
/*
* c->c_tosp is 1/c->c_fromsp, but we will invert the expression
* above in the hopes of some extra accuracy.
*
* IS THIS ANY GOOD? I NEED A NUMERICAL ANALYST!
*/
c->c_tosp = (254000.0 / num) * (denom / ddpi) * (1.0 / c->c_mag);
}