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#include <stdio.h>
#include <math.h>
#include <stdlib.h>
#include <string.h>
/*
* adapted from Paul Heckbert's algorithm on p 657-659 of
* Andrew S. Glassner's book, "Graphics Gems"
* ISBN 0-12-286166-3
*
*/
#include "tickmarks.h"
#define MAX(a, b) (((a) < (b)) ? (b) : (a))
static double nicenum(double x, int round)
{
int exp; /* exponent of x */
double f; /* fractional part of x */
exp = floor(log10(x));
f = x / pow(10.0, exp);
if (round) {
if (f < 1.5)
return 1.0 * pow(10.0, exp);
if (f < 3.0)
return 2.0 * pow(10.0, exp);
if (f < 7.0)
return 5.0 * pow(10.0, exp);
return 10.0 * pow(10.0, exp);
}
if (f <= 1.0)
return 1.0 * pow(10.0, exp);
if (f <= 2.0)
return 2.0 * pow(10.0, exp);
if (f <= 5.0)
return 5.0 * pow(10.0, exp);
return 10.0 * pow(10.0, exp);
}
static void shorten(struct tickmark *tm, int nticks, int *power_of_ten,
int use_KMG_symbols, int base_offset)
{
const char shorten_chr[] = { 0, 'K', 'M', 'G', 'P', 'E', 0 };
int i, l, minshorten, shorten_idx = 0;
char *str;
minshorten = 100;
for (i = 0; i < nticks; i++) {
str = tm[i].string;
l = strlen(str);
if (strcmp(str, "0") == 0)
continue;
if (l > 9 && strcmp(&str[l - 9], "000000000") == 0) {
*power_of_ten = 9;
shorten_idx = 3;
} else if (6 < minshorten && l > 6 &&
strcmp(&str[l - 6], "000000") == 0) {
*power_of_ten = 6;
shorten_idx = 2;
} else if (l > 3 && strcmp(&str[l - 3], "000") == 0) {
*power_of_ten = 3;
shorten_idx = 1;
} else {
*power_of_ten = 0;
}
if (*power_of_ten < minshorten)
minshorten = *power_of_ten;
}
if (minshorten == 0)
return;
if (!use_KMG_symbols)
shorten_idx = 0;
else if (base_offset)
shorten_idx += base_offset;
for (i = 0; i < nticks; i++) {
str = tm[i].string;
l = strlen(str);
str[l - minshorten] = shorten_chr[shorten_idx];
if (shorten_idx)
str[l - minshorten + 1] = '\0';
}
}
int calc_tickmarks(double min, double max, int nticks, struct tickmark **tm,
int *power_of_ten, int use_KMG_symbols, int base_offset)
{
char str[100];
int nfrac;
double d; /* tick mark spacing */
double graphmin, graphmax; /* graph range min and max */
double range, x;
int count, i;
/* we expect min != max */
range = nicenum(max - min, 0);
d = nicenum(range / (nticks - 1), 1);
graphmin = floor(min / d) * d;
graphmax = ceil(max / d) * d;
nfrac = MAX(-floor(log10(d)), 0);
snprintf(str, sizeof(str)-1, "%%.%df", nfrac);
count = ((graphmax + 0.5 * d) - graphmin) / d + 1;
*tm = malloc(sizeof(**tm) * count);
i = 0;
for (x = graphmin; x < graphmax + 0.5 * d; x += d) {
(*tm)[i].value = x;
sprintf((*tm)[i].string, str, x);
i++;
}
shorten(*tm, i, power_of_ten, use_KMG_symbols, base_offset);
return i;
}
#if 0
static void test_range(double x, double y)
{
int nticks, i;
struct tickmark *tm = NULL;
printf("Testing range %g - %g\n", x, y);
nticks = calc_tickmarks(x, y, 10, &tm);
for (i = 0; i < nticks; i++)
printf(" (%s) %g\n", tm[i].string, tm[i].value);
printf("\n\n");
free(tm);
}
int main(int argc, char *argv[])
{
test_range(0.0005, 0.008);
test_range(0.5, 0.8);
test_range(5.5, 8.8);
test_range(50.5, 80.8);
test_range(-20, 20.8);
test_range(-30, 700.8);
}
#endif
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