110 lines
2.4 KiB
C
110 lines
2.4 KiB
C
|
/***
|
||
|
|
**
|
||
|
|
** Module: Trig
|
||
|
|
**
|
||
|
|
** Description:
|
||
|
|
** This is a module of the T1 to TT font converter. The module
|
||
|
|
** contains a look-up table for computing atan2() faster, and
|
||
|
|
** with less precision than that of the c run-time library.
|
||
|
|
**
|
||
|
|
** Author: Michael Jansson
|
||
|
|
**
|
||
|
|
** Created: 5/26/93
|
||
|
|
**
|
||
|
|
***/
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
#include "types.h"
|
||
|
|
#include "metrics.h"
|
||
|
|
#include "trig.h"
|
||
|
|
|
||
|
|
static const unsigned char atan_tbl[] = {
|
||
|
|
0,
|
||
|
|
2, 5, 7, 10, 12, 15, 17, 20, 22, 25, 27, 30, 32, 35, 38, 40,
|
||
|
|
43, 45, 48, 50, 53, 55, 57, 60, 62, 65, 67, 70, 72, 75, 77, 79,
|
||
|
|
82, 84, 87, 89, 91, 94, 96, 98, 101, 103, 105, 107, 110, 112, 114, 116,
|
||
|
|
119, 121, 123, 125, 127, 130, 132, 134, 136, 138, 140, 142, 144, 147, 149, 151,
|
||
|
|
153, 155, 157, 159, 161, 163, 165, 167, 168, 170, 172, 174, 176, 178, 180, 182,
|
||
|
|
183, 185, 187, 189, 191, 192, 194, 196, 198, 199, 201, 203, 204, 206, 208, 209,
|
||
|
|
211, 212, 214, 216, 217, 219, 220, 222, 223, 225, 226, 228, 229, 231, 232, 234,
|
||
|
|
235, 237, 238, 239, 241, 242, 244, 245, 246, 248, 249, 250, 252, 253, 254, 255
|
||
|
|
};
|
||
|
|
|
||
|
|
|
||
|
|
/***
|
||
|
|
** Function: Atan2
|
||
|
|
**
|
||
|
|
** Description:
|
||
|
|
** Compute atan2()
|
||
|
|
***/
|
||
|
|
int FASTCALL Atan2(const funit dy, const funit dx)
|
||
|
|
{
|
||
|
|
funit du, dv;
|
||
|
|
int a = 0;
|
||
|
|
|
||
|
|
/* Normalize the sign. */
|
||
|
|
if (ABS(dx)>ABS(dy)) {
|
||
|
|
du = ABS(dx);
|
||
|
|
dv = ABS(dy);
|
||
|
|
|
||
|
|
if (du==0) {
|
||
|
|
a = PI4;
|
||
|
|
} else {
|
||
|
|
|
||
|
|
/* Normalize for the size of the table. */
|
||
|
|
while (dv>256) {
|
||
|
|
dv = (dv+1)>>1;
|
||
|
|
du = (du+1)>>1;
|
||
|
|
}
|
||
|
|
dv = ((dv<<7)+(du>>1))/du;
|
||
|
|
|
||
|
|
/* Lookup the angle. */
|
||
|
|
if (dv==1)
|
||
|
|
a = (int)((long)PI4 * (long)ABS(dx) / (long)ABS(dy));
|
||
|
|
if (du!=dv)
|
||
|
|
a = (int)atan_tbl[dv];
|
||
|
|
}
|
||
|
|
|
||
|
|
} else {
|
||
|
|
du = ABS(dy);
|
||
|
|
dv = ABS(dx);
|
||
|
|
|
||
|
|
if (du==0) {
|
||
|
|
a = PI4;
|
||
|
|
} else {
|
||
|
|
|
||
|
|
/* Normalize for the size of the table. */
|
||
|
|
while (dv>256) {
|
||
|
|
dv = (dv+1)>>1;
|
||
|
|
du = (du+1)>>1;
|
||
|
|
}
|
||
|
|
dv = ((dv<<7)+(du>>1))/du;
|
||
|
|
|
||
|
|
/* Lookup the angle. */
|
||
|
|
if (dv==1)
|
||
|
|
a = (int)((long)PI4 * (long)ABS(dy) / (long)ABS(dx));
|
||
|
|
if (du!=dv)
|
||
|
|
a = PI2 - (int)atan_tbl[dv];
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
|
||
|
|
/* pick the right quadrant. */
|
||
|
|
if (dx>0) {
|
||
|
|
if (dy>0) {
|
||
|
|
/* NOOP */
|
||
|
|
} else {
|
||
|
|
a = -a;
|
||
|
|
}
|
||
|
|
} else {
|
||
|
|
if (dy>0) {
|
||
|
|
a = PI - a;
|
||
|
|
} else {
|
||
|
|
a = a - PI;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
return a;
|
||
|
|
}
|